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Artificial intelligence is expected to have tremendous societal impact across the globe in the near future. Now Luis Videgaray PhD ’98, former foreign minister and finance minister of Mexico, is coming to MIT to spearhead an effort that aims to help shape global AI policies, focusing on how such rising technologies will affect people living in all corners of the world.
Starting this month, Videgaray, an expert in geopolitics and AI policy, will serve as director of the MIT Artificial Intelligence Policy for the World Project (MIT AIPW), a collaboration between the MIT Sloan School of Management and the new MIT Stephen A. Schwarzman College of Computing. Videgaray will also serve as a senior lecturer at the MIT Sloan and as a distinguished fellow at the MIT Internet Policy Research Initiative.
The MIT AIPW will bring together researchers from across the Institute to explore and analyze best AI policies for countries around the world based on various geopolitical considerations. The end result of the year-long effort, Videgaray says, will be a report with actionable policy recommendations for national and local governments, businesses, international organizations, and universities — including MIT.
“The core idea is to analyze, raise awareness, and come up with useful policy recommendations for how the geopolitical context affects both the development and use of AI,” says Videgaray, who earned his PhD at MIT in economics. “It’s called AI Policy for the World, because it’s not only about understanding the geopolitics, but also includes thinking about people in poor nations, where AI is not really being developed but will be adopted and have significant impact in all aspects of life.”
“When we launched the MIT Stephen A. Schwarzman College of Computing, we expressed the desire for the college to examine the societal implications of advanced computational capabilities,” says MIT Provost Martin Schmidt. “One element of that is developing frameworks which help governments and policymakers contemplate these issues. I am delighted to see us jump-start this effort with the leadership of our distinguished alumnus, Dr. Videgaray.”
Democracy, diversity, and de-escalation
As Mexico’s finance minister from 2012 to 2016, Videgaray led Mexico’s energy liberalization process, a telecommunications reform to foster competition in the sector, a tax reform that reduced the country’s dependence on oil revenues, and the drafting of the country’s laws on financial technology. In 2012, he was campaign manager for President Peña Nieto and head of the presidential transition team.
As foreign minister from 2017 to 2018, Videgaray led Mexico’s relationship with the Trump White House, including the renegotiation of the North American Free Trade Agreement (NAFTA). He is one of the founders of the Lima Group, created to promote regional diplomatic efforts toward restoring democracy in Venezuela. He also directed Mexico’s leading role in the UN toward an inclusive debate on artificial intelligence and other new technologies. In that time, Videgaray says AI went from being a “science-fiction” concept in the first year to a major global political issue the following year.
In the past few years, academic institutions, governments, and other organizations have launched initiatives that address those issues, and more than 20 countries have strategies in place that guide AI development. But they miss a very important point, Videgaray says: AI’s interaction with geopolitics.
MIT AIWP will have three guiding principles to help shape policy around geopolitics: democratic values, diversity and inclusion, and de-escalation.
One of the most challenging and important issues MIT AIWP faces is if AI “can be a threat to democracy,” Videgaray says. In that way, the project will explore policies that help advance AI technologies, while upholding the values of liberal democracy.
“We see some countries starting to adopt AI technologies not for the improvement for the quality of life, but for social control,” he says. “This technology can be extremely powerful, but we are already seeing how it can also be used to … influence people and have an effect on democracy. In countries where institutions are not as strong, there can be an erosion of democracy.”
A policy challenge in that regard is how to deal with private data restrictions in different countries. If some countries don’t put any meaningful restrictions on data usage, it could potentially give them a competitive edge. “If people start thinking about geopolitical competition as more important than privacy, biases, or algorithmic transparency, and the concern is to win at all costs, then the societal impact of AI around the world could be quite worrisome,” Videgaray says.
In the same vein, MIT AIPW will focus on de-escalation of potential conflict, by promoting an analytical, practical, and realistic collaborative approach to developing and using AI technologies. While media has dubbed the rise of AI worldwide as a type of “arms race,” Videgaray says that type of thinking is potentially hazardous to society. “That reflects a sentiment that we’re moving again into an adversarial world, and technology will be a huge part of it,” he says. “That will have negative effects of how technology is developed and used.”
For inclusion and diversity, the project will make AI’s ethical impact “a truly global discussion,” Videgaray says. That means promoting awareness and participation from countries around the world, including those that may be less developed and more vulnerable. Another challenge is deciding not only what policies should be implemented, but also where those policies might be best implemented. That could mean at the state level or national level in the United States, in different European countries, or with the UN.
“We want to approach this in a truly inclusive way, which is not just about countries leading development of technology,” Videgaray says. “Every country will benefit and be negatively affected by AI, but many countries are not part of the discussion.”
While MIT AIPW won’t be drafting international agreements, Videgaray says another aim of the project is to explore different options and elements of potential international agreements. He also hopes to reach out to decision makers in governments and businesses around the world to gather feedback on the project’s research.
Part of Videgaray’s role includes building connections across MIT departments, labs, and centers to pull in researchers to focus on the issue. “For this to be successful, we need to integrate the thinking of people from different backgrounds and expertise,” he says.
At MIT Sloan, Videgaray will teach classes alongside Simon Johnson, the Ronald A. Kurtz Professor of Entrepreneurship Professor and a professor of global economics and management. His lectures will focus primarily on the issues explored by the MIT AIPW project.
Next spring, MIT AIPW plans to host a conference at MIT to convene researchers from the Institute and around the world to discuss the project’s initial findings and other topics in AI.
As a cucumber plant grows, it sprouts tightly coiled tendrils that seek out supports in order to pull the plant upward. This ensures the plant receives as much sunlight exposure as possible. Now, researchers at MIT have found a way to imitate this coiling-and-pulling mechanism to produce contracting fibers that could be used as artificial muscles for robots, prosthetic limbs, or other mechanical and biomedical applications.
While many different approaches have been used for creating artificial muscles, including hydraulic systems, servo motors, shape-memory metals, and polymers that respond to stimuli, they all have limitations, including high weight or slow response times. The new fiber-based system, by contrast, is extremely lightweight and can respond very quickly, the researchers say. The findings are being reported today in the journal Science.
The new fibers were developed by MIT postdoc Mehmet Kanik and MIT graduate student Sirma Örgüç, working with professors Polina Anikeeva, Yoel Fink, Anantha Chandrakasan, and C. Cem Taşan, and five others, using a fiber-drawing technique to combine two dissimilar polymers into a single strand of fiber.
The key to the process is mating together two materials that have very different thermal expansion coefficients — meaning they have different rates of expansion when they are heated. This is the same principle used in many thermostats, for example, using a bimetallic strip as a way of measuring temperature. As the joined material heats up, the side that wants to expand faster is held back by the other material. As a result, the bonded material curls up, bending toward the side that is expanding more slowly.
Credit: Courtesy of the researchers
Using two different polymers bonded together, a very stretchable cyclic copolymer elastomer and a much stiffer thermoplastic polyethylene, Kanik, Örgüç and colleagues produced a fiber that, when stretched out to several times its original length, naturally forms itself into a tight coil, very similar to the tendrils that cucumbers produce. But what happened next actually came as a surprise when the researchers first experienced it. “There was a lot of serendipity in this,” Anikeeva recalls.
As soon as Kanik picked up the coiled fiber for the first time, the warmth of his hand alone caused the fiber to curl up more tightly. Following up on that observation, he found that even a small increase in temperature could make the coil tighten up, producing a surprisingly strong pulling force. Then, as soon as the temperature went back down, the fiber returned to its original length. In later testing, the team showed that this process of contracting and expanding could be repeated 10,000 times “and it was still going strong,” Anikeeva says.
Credit: Courtesy of the researchers
One of the reasons for that longevity, she says, is that “everything is operating under very moderate conditions,” including low activation temperatures. Just a 1-degree Celsius increase can be enough to start the fiber contraction.
The fibers can span a wide range of sizes, from a few micrometers (millionths of a meter) to a few millimeters (thousandths of a meter) in width, and can easily be manufactured in batches up to hundreds of meters long. Tests have shown that a single fiber is capable of lifting loads of up to 650 times its own weight. For these experiments on individual fibers, Örgüç and Kanik have developed dedicated, miniaturized testing setups.
Credit: Courtesy of the researchers
The degree of tightening that occurs when the fiber is heated can be “programmed” by determining how much of an initial stretch to give the fiber. This allows the material to be tuned to exactly the amount of force needed and the amount of temperature change needed to trigger that force.
The fibers are made using a fiber-drawing system, which makes it possible to incorporate other components into the fiber itself. Fiber drawing is done by creating an oversized version of the material, called a preform, which is then heated to a specific temperature at which the material becomes viscous. It can then be pulled, much like pulling taffy, to create a fiber that retains its internal structure but is a small fraction of the width of the preform.
For testing purposes, the researchers coated the fibers with meshes of conductive nanowires. These meshes can be used as sensors to reveal the exact tension experienced or exerted by the fiber. In the future, these fibers could also include heating elements such as optical fibers or electrodes, providing a way of heating it internally without having to rely on any outside heat source to activate the contraction of the “muscle.”
Such fibers could find uses as actuators in robotic arms, legs, or grippers, and in prosthetic limbs, where their slight weight and fast response times could provide a significant advantage.
Some prosthetic limbs today can weigh as much as 30 pounds, with much of the weight coming from actuators, which are often pneumatic or hydraulic; lighter-weight actuators could thus make life much easier for those who use prosthetics. Such fibers might also find uses in tiny biomedical devices, such as a medical robot that works by going into an artery and then being activated,” Anikeeva suggests. “We have activation times on the order of tens of milliseconds to seconds,” depending on the dimensions, she says.
To provide greater strength for lifting heavier loads, the fibers can be bundled together, much as muscle fibers are bundled in the body. The team successfully tested bundles of 100 fibers. Through the fiber drawing process, sensors could also be incorporated in the fibers to provide feedback on conditions they encounter, such as in a prosthetic limb. Örgüç says bundled muscle fibers with a closed-loop feedback mechanism could find applications in robotic systems where automated and precise control are required.
Kanik says that the possibilities for materials of this type are virtually limitless, because almost any combination of two materials with different thermal expansion rates could work, leaving a vast realm of possible combinations to explore. He adds that this new finding was like opening a new window, only to see “a bunch of other windows” waiting to be opened.
“The strength of this work is coming from its simplicity,” he says.
The team also included MIT graduate student Georgios Varnavides, postdoc Jinwoo Kim, and undergraduate students Thomas Benavides, Dani Gonzalez, and Timothy Akintlio. The work was supported by the National Institute of Neurological Disorders and Stroke and the National Science Foundation.
A promising new way to treat some types of cancer is to program the patient’s own T cells to destroy the cancerous cells. This approach, termed CAR-T cell therapy, is now used to combat some types of leukemia, but so far it has not worked well against solid tumors such as lung or breast tumors.
MIT researchers have now devised a way to super-charge this therapy so that it could be used as a weapon against nearly any type of cancer. The research team developed a vaccine that dramatically boosts the antitumor T cell population and allows the cells to vigorously invade solid tumors.
In a study of mice, the researchers found that they could completely eliminate solid tumors in 60 percent of the animals that were given T-cell therapy along with the booster vaccination. Engineered T cells on their own had almost no effect.
“By adding the vaccine, a CAR-T cell treatment which had no impact on survival can be amplified to give a complete response in more than half of the animals,” says Darrell Irvine, who is the Underwood-Prescott Professor with appointments in Biological Engineering and Materials Science and Engineering, an associate director of MIT’s Koch Institute for Integrative Cancer Research, a member of the Ragon Institute of MGH, MIT, and Harvard, and the senior author of the study.
Leyuan Ma, an MIT postdoc, is the lead author of the study, which appears in the July 11 online edition of Science.
So far, the FDA has approved two types of CAR-T cell therapy, both used to treat leukemia. In those cases, T cells removed from the patient’s blood are programmed to target a protein, or antigen, found on the surface of B cells. (The “CAR” in CAR-T cell therapy is for “chimeric antigen receptor.”)
Scientists believe one reason this approach hasn’t worked well for solid tumors is that tumors usually generate an immunosuppressive environment that disarms the T cells before they can reach their target. The MIT team decided to try to overcome this by giving a vaccine that would go to the lymph nodes, which host huge populations of immune cells, and stimulate the CAR-T cells there.
“Our hypothesis was that if you boosted those T cells through their CAR receptor in the lymph node, they would receive the right set of priming cues to make them more functional so they’d be resistant to shutdown and would still function when they got into the tumor,” Irvine says.
To create such a vaccine, the MIT team used a trick they had discovered several years ago. They found that they could deliver vaccines more effectively to the lymph nodes by linking them to a fatty molecule called a lipid tail. This lipid tail binds to albumin, a protein found in the bloodstream, allowing the vaccine to hitch a ride directly to the lymph nodes.
In addition to the lipid tail, the vaccine contains an antigen that stimulates the CAR-T cells once they reach the lymph nodes. This antigen could be either the same tumor antigen targeted by the T cells, or an arbitrary molecule chosen by the researchers. For the latter case, the CAR-T cells have to be re-engineered so that they can be activated by both the tumor antigen and the arbitrary antigen.
In tests in mice, the researchers showed that either of these vaccines dramatically enhanced the T-cell response. When mice were given about 50,000 CAR-T cells but no vaccine, the CAR-T cells were nearly undetectable in the animals’ bloodstream. In contrast, when the booster vaccine was given the day after the T-cell infusion, and again a week later, CAR-T cells expanded until they made up 65 percent of the animals’ total T cell population, two weeks after treatment.
This huge boost in the CAR-T cell population translated to complete elimination of glioblastoma, breast, and melanoma tumors in many of the mice. CAR-T cells given without the vaccine had no effect on tumors, while CAR-T cells given with the vaccine eliminated tumors in 60 percent of the mice.
This technique also holds promise for preventing tumor recurrence, Irvine says. About 75 days after the initial treatment, the researchers injected tumor cells identical to those that formed the original tumor, and these cells were cleared by the immune system. About 50 days after that, the researchers injected slightly different tumor cells, which did not express the antigen that the original CAR-T cells targeted; the mice could also eliminate those tumor cells.
This suggests that once the CAR-T cells begin destroying tumors, the immune system is able to detect additional tumor antigens and generate populations of “memory” T cells that also target those proteins.
“If we take the animals that appear to be cured and we rechallenge them with tumor cells, they will reject all of them,” Irvine says. “That is another exciting aspect of this strategy. You need to have T cells attacking many different antigens to succeed, because if you have a CAR-T cell that sees only one antigen, then the tumor only has to mutate that one antigen to escape immune attack. If the therapy induces new T-cell priming, this kind of escape mechanism becomes much more difficult.”
While most of the study was done in mice, the researchers showed that human cells coated with CAR antigens also stimulated human CAR-T cells, suggesting that the same approach could work in human patients. The technology has been licensed to a company called Elicio Therapeutics, which is seeking to test it with CAR-T cell therapies that are already in development.
“There’s really no barrier to doing this in patients pretty soon, because if we take a CAR-T cell and make an arbitrary peptide ligand for it, then we don’t have to change the CAR-T cells,” Irvine says. “I’m hopeful that one way or another this can get tested in patients in the next one to two years.”
The research was funded by the National Institutes of Health, the Marble Center for Cancer Nanomedicine, Johnson and Johnson, and the National Institute of General Medical Sciences.
CRISPR-based tools have revolutionized our ability to target disease-linked genetic mutations. CRISPR technology comprises a growing family of tools that can manipulate genes and their expression, including by targeting DNA with the enzymes Cas9 and Cas12 and targeting RNA with the enzyme Cas13. This collection offers different strategies for tackling mutations. Targeting disease-linked mutations in RNA, which is relatively short-lived, would avoid making permanent changes to the genome. In addition, some cell types, such as neurons, are difficult to edit using CRISPR/Cas9-mediated editing, and new strategies are needed to treat devastating diseases that affect the brain.
McGovern Institute Investigator and Broad Institute of MIT and Harvard core member Feng Zhang and his team have now developed one such strategy, called RESCUE (RNA Editing for Specific C to U Exchange), described in the journal Science.
Zhang and his team, including first co-authors Omar Abudayyeh and Jonathan Gootenberg (both now McGovern fellows), made use of a deactivated Cas13 to guide RESCUE to targeted cytosine bases on RNA transcripts, and used a novel, evolved, programmable enzyme to convert unwanted cytosine into uridine — thereby directing a change in the RNA instructions. RESCUE builds on REPAIR, a technology developed by Zhang’s team that changes adenine bases into inosine in RNA.
RESCUE significantly expands the landscape that CRISPR tools can target to include modifiable positions in proteins, such as phosphorylation sites. Such sites act as on/off switches for protein activity and are notably found in signaling molecules and cancer-linked pathways.
“To treat the diversity of genetic changes that cause disease, we need an array of precise technologies to choose from. By developing this new enzyme and combining it with the programmability and precision of CRISPR, we were able to fill a critical gap in the toolbox,” says Zhang, the James and Patricia Poitras Professor of Neuroscience at MIT. Zhang has appointments in MIT’s departments of Brain and Cognitive Sciences and Biological Engineering.
Expanding the reach of RNA editing to new targets
The previously developed REPAIR platform used the RNA-targeting CRISPR/Cas13 to direct the active domain of an RNA editor, ADAR2, to specific RNA transcripts where it could convert the nucleotide base adenine to inosine, or letters A to I. Zhang and colleagues took the REPAIR fusion and evolved it in the lab until it could change cytosine to uridine, or C to U.
RESCUE can be guided to any RNA of choice, then perform a C-to-U edit through the evolved ADAR2 component of the platform. The team took the new platform into human cells, showing that they could target natural RNAs in the cell, as well as 24 clinically relevant mutations in synthetic RNAs. They then further optimized RESCUE to reduce off-target editing, while minimally disrupting on-target editing.
New targets in sight
Expanded targeting by RESCUE means that sites regulating activity and function of many proteins through post-translational modifications, such as phosphorylation, glycosylation, and methylation, can now be more readily targeted for editing.
A major advantage of RNA editing is its reversibility, in contrast to changes made at the DNA level, which are permanent. Thus, RESCUE could be deployed transiently in situations where a modification may be desirable temporarily, but not permanently. To demonstrate this, the team showed that in human cells, RESCUE can target specific sites in the RNA encoding β-catenin, that are known to be phosphorylated on the protein product, leading to a temporary increase in β-catenin activation and cell growth. If such a change were made permanent, it could predispose cells to uncontrolled cell growth and cancer, but by using RESCUE, transient cell growth could potentially stimulate wound healing in response to acute injuries.
The researchers also targeted a pathogenic gene variant, APOE4. The APOE4 allele has consistently emerged as a genetic risk factor for the development of late-onset Alzheimer’s disease. Isoform APOE4 differs from APOE2, which is not a risk factor, by just two differences (both C in APOE4 versus U in APOE2). Zhang and colleagues introduced the risk-associated APOE4 RNA into cells and showed that RESCUE can convert its signature Cs to an APOE2 sequence, essentially converting a risk to a non-risk variant.
To facilitate additional work that will push RESCUE toward the clinic, as well as enable researchers to use RESCUE as a tool to better understand disease-causing mutations, the Zhang lab plans to share the RESCUE system broadly, as they have with previously developed CRISPR tools. The technology will be freely available for academic research through the nonprofit plasmid repository Addgene. Additional information can be found on the Zhang lab’s webpage.
Support for the study was provided by The Phillips Family; J. and P. Poitras; the Poitras Center for Psychiatric Disorders Research; Hock E. Tan and K. Lisa Yang Center for Autism Research; Robert Metcalfe; David Cheng; and a Natinoal Institutes of Heatlh grant to Omar Abudayyeh. Feng Zhang is a New York Stem Cell Foundation–Robertson Investigator. Feng Zhang is supported by the National Institutes of Health; the Howard Hughes Medical Institute; the New York Stem Cell Foundation, and G. Harold and Leila Mathers Foundations.
Researchers at MIT have come up with a new pulsed laser deposition technique to make thinner lithium electrolytes using less heat, promising faster charging and potentially higher-voltage solid-state lithium ion batteries.
Key to the new technique for processing the solid-state battery electrolyte is alternating layers of the active electrolyte lithium garnet component (chemical formula, Li6.25Al0.25La3Zr2O12, or LLZO) with layers of lithium nitride (chemical formula Li3N). First, these layers are built up like a wafer cookie using a pulsed laser deposition process at about 300 degrees Celsius (572 degrees Fahrenheit). Then they are heated to 660 C and slowly cooled, a process known as annealing.
During the annealing process, nearly all of the nitrogen atoms burn off into the atmosphere and the lithium atoms from the original nitride layers fuse into the lithium garnet, forming a single lithium-rich, ceramic thin film. The extra lithium content in the garnet film allows the material to retain the cubic structure needed for positively charged lithium ions (cations) to move quickly through the electrolyte. The findings were reported in a Nature Energy paper published online recently by MIT Associate Professor Jennifer L. M. Rupp and her students Reto Pfenninger, Michal M. Struzik, Inigo Garbayo, and collaborator Evelyn Stilp.
“The really cool new thing is that we found a way to bring the lithium into the film at deposition by using lithium nitride as an internal lithiation source,” Rupp, the work's senior author, says. Rupp holds joint MIT appointments in the departments of Materials Science and Engineering and Electrical Engineering and Computer Science.
“The second trick to the story is that we use lithium nitride, which is close in bandgap to the laser that we use in the deposition, whereby we have a very fast transfer of the material, which is another key factor to not lose lithium to evaporation during a pulsed laser deposition,” Rupp explains.
Lithium batteries with commonly used electrolytes made by combining a liquid and a polymer can pose a fire risk when the liquid is exposed to air. Solid-state batteries are desirable because they replace the commonly used liquid polymer electrolytes in consumer lithium batteries with a solid material that is safer. “So we can kick that out, bring something safer in the battery, and decrease the electrolyte component in size by a factor of 100 by going from the polymer to the ceramic system,” Rupp explains.
Although other methods to produce lithium-rich ceramic materials on larger pellets or tapes, heated using a process called sintering, can yield a dense microstructure that retains a high lithium concentration, they require higher heat and result in bulkier material. The new technique pioneered by Rupp and her students produces a thin film that is about 330 nanometers thick (less than 1.5 hundred-thousandths of an inch). “Having a thin film structure instead of a thick ceramic is attractive for battery electrolyte in general because it allows you to have more volume in the electrodes, where you want to have the active storage capacity. So the holy grail is be thin and be fast,” she says.
Compared to the classic ceramic coffee mug, which under high magnification shows metal oxide particles with a grain size of tens to hundreds of microns, the lithium (garnet) oxide thin films processed using Rupp’s methods show nanometer scale grain structures that are one-thousandth to one-ten-thousandth the size. That means Rupp can engineer thinner electrolytes for batteries. “There is no need in a solid-state battery to have a large electrolyte,” she says.
Faster ionic conduction
Instead, what is needed is an electrolyte with faster conductivity. The unit of measurement for lithium ion conductivity is expressed in Siemens. The new multilayer deposition technique produces a lithium garnet (LLZO) material that shows the fastest ionic conductivity yet for a lithium-based electrolyte compound, about 2.9 x 10-5 Siemens (0.000029 Siemens) per centimeter. This ionic conductivity is competitive with solid-state lithium battery thin film electrolytes based on LIPON (lithium phosphorus oxynitride electrolytes) and adds a new film electrolyte material to the landscape.
“Having the lithium electrolyte as a solid-state very fast conductor allows you to dream out loud of anything else you can do with fast lithium motion,” Rupp says.
A battery’s negatively charged electrode stores power. The work points the way toward higher-voltage batteries based on lithium garnet electrolytes, both because its lower processing temperature opens the door to using materials for higher voltage cathodes that would be unstable at higher processing temperatures, and its smaller electrolyte size allows physically larger cathode volume in the same battery size.
Co-authors Michal Struzik and Reto Pfenninger carried out processing and Raman spectroscopy measurements on the lithium garnet material. These measurements were key to showing the material’s fast conduction at room temperature, as well as understanding the evolution of its different structural phases.
“One of the main challenges in understanding the development of the crystal structure in LLZO was to develop appropriate methodology. We have proposed a series of experiments to observe development of the crystal structure in the [LLZO] thin film from disordered or 'amorphous' phase to fully crystalline, highly conductive phase utilizing Raman spectroscopy upon thermal annealing under controlled atmospheric conditions,” says co-author Struzik, who was a postdoc working at ETH Zurich and MIT with Rupp’s group, and is now a professor at Warsaw University of Technology in Poland. “That allowed us to observe and understand how the crystal phases are developed and, as a consequence, the ionic conductivity improved,” he explains.
Their work shows that during the annealing process, lithium garnet evolves from the amorphous phase in the initial multilayer processed at 300 C through progressively higher temperatures to a low conducting tetragonal phase in a temperature range from about 585 C to 630 C, and to the desired highly conducting cubic phase after annealing at 660 C. Notably, this temperature of 660 C to achieve the highly conducting phase in the multilayer approach is nearly 400 C lower than the 1,050 C needed to achieve it with prior sintering methods using pellets or tapes.
“One of the greatest challenges facing the realization of solid-state batteries lies in the ability to fabricate such devices. It is tough to bring the manufacturing costs down to meet commercial targets that are competitive with today's liquid-electrolyte-based lithium-ion batteries, and one of the main reasons is the need to use high temperatures to process the ceramic solid electrolytes,” says Professor Peter Bruce, the Wolfson Chair of the Department of Materials at Oxford University, who was not involved in this research.
“This important paper reports a novel and imaginative approach to addressing this problem by reducing the processing temperature of garnet-based solid-state batteries by more than half — that is, by hundreds of degrees,” Bruce adds. “Normally, high temperatures are required to achieve sufficient solid-state diffusion to intermix the constituent atoms of ceramic electrolyte. By interleaving lithium layers in an elegant nanostructure the authors have overcome this barrier.”
After demonstrating the novel processing and high conductivity of the lithium garnet electrode, the next step will be to test the material in an actual battery to explore how the material reacts with a battery cathode and how stable it is. “There is still a lot to come,” Rupp predicts.
Understanding aluminum dopant sites
A small fraction of aluminum is added to the lithium garnet formulation because aluminum is known to stabilize the highly conductive cubic phase in this high-temperature ceramic. The researchers complemented their Raman spectroscopy analysis with another technique, known as negative-ion time-of-flight secondary ion mass spectrometry (TOF-SIMS), which shows that the aluminum retains its position at what were originally the interfaces between the lithium nitride and lithium garnet layers before the heating step expelled the nitrogen and fused the material.
“When you look at large-scale processing of pellets by sintering, then everywhere where you have a grain boundary, you will find close to it a higher concentration of aluminum. So we see a replica of that in our new processing, but on a smaller scale at the original interfaces,” Rupp says. “These little things are what adds up, also, not only to my excitement in engineering but my excitement as a scientist to understand phase formations, where that goes and what that does,” Rupp says.
“Negative TOF-SIMS was indeed challenging to measure since it is more common in the field to perform this experiment with focus on positively charged ions,” explains Pfenninger, who worked at ETH Zurich and MIT with Rupp’s group. “However, for the case of the negatively charged nitrogen atoms we could only track it in this peculiar setup. The phase transformations in thin films of LLZO have so far not been investigated in temperature-dependent Raman spectroscopy — another insight towards the understanding thereof.”
The paper’s other authors are Inigo Garbayo, who is now at CIC EnergiGUNE in Minano, Spain, and Evelyn Stilp, who was then with Empa, Swiss Federal Laboratories for Materials Science and Technology, in Dubendorf, Switzerland.
Rupp began this research while serving as a professor of electrochemical materials at ETH Zurich (the Swiss Federal Institute of Technology) before she joined the MIT faculty in February 2017. MIT and ETH have jointly filed for two patents on the multi-layer lithium garnet/lithium nitride processing. This new processing method, which allows precise control of lithium concentration in the material, can also be applied to other lithium oxide films such as lithium titanate and lithium cobaltate that are used in battery electrodes. “That is something we invented. That’s new in ceramic processing,” Rupp says.
“It is a smart idea to use Li3N as a lithium source during preparation of the garnet layers, as lithium loss is a critical issue during thin film preparation otherwise,” comments University Professor Jürgen Janek at Justus Liebig University Giessen in Germany. Janek, who was not involved in this research, adds that “the quality of the data and the analysis is convincing.”
“This work is an exciting first step in preparing one of the best oxide-based solid electrolytes in an intermediate temperature range,” Janek says. “It will be interesting to see whether the intermediate temperature of about 600 degrees C is sufficient to avoid side reactions with the electrode materials.”
Oxford Professor Bruce notes the novelty of the approach, adding “I'm not aware of similar nanostructured approaches to reduce diffusion lengths in solid-state synthesis.”
“Although the paper describes specific application of the approach to the formation of lithium-rich and therefore highly conducting garnet solid electrolytes, the methodology has more general applicability, and therefore significant potential beyond the specific examples provided in the paper,” Bruce says. Commercialization may be needed to be demonstrate this approach at larger scale, he suggests.
While the immediate impact of this work is likely to be on batteries, Rupp predicts another decade of exciting advances based on applications of her processing techniques to devices for neuromorphic computing, artificial intelligence, and fast gas sensors. “The moment the lithium is in a small solid-state film, you can use the fast motion to trigger other electrochemistry,” she says.
Several companies have already expressed interest in using the new electrolyte approach. “It’s good for me to work with strong players in the field so they can push out the technology faster than anything I can do,” Rupp says.
This work was funded by the MIT Lincoln Laboratory, the Thomas Lord Foundation, Competence Center Energy and Mobility, and Swiss Electrics.
Genevieve Barnard Oni’s iPhone lights up with the same notifications dozens of times each day — but they aren’t from a popular Instagram account or an overactive group chat. Instead, the notifications signal every time a patient is treated at MDaaS Global’s health clinic in Ibadan, Nigeria.
Last month Barnard Oni MBA ’19, who co-founded the company with her husband, Oluwasoga (Soga) Oni SM ’16, as well as Joe McCord SM ’15 and Opeyemi Ologun, received 750 such notifications. If all goes according to plan, that number is about to multiply.
Operating outside of the wealthier, well-resourced city center, the company’s clinic offers affordable diagnostic services, including ultrasounds, X-rays, malaria tests, and other lab services, that were previously inaccessible to many families in the area.
MDaaS has accomplished this by building a supply chain that gets refurbished medical equipment into the African communities that need them most, and by leveraging technology to streamline clinic operations.
By partnering with dozens of nearby hospitals and clinics to get patient referrals, the MDaaS clinic has diagnosed more than 10,000 patients since opening less than two years ago. Now, fresh off a $1 million funding round, the company is planning to export its model to other areas of Nigeria and West Africa, with the goal of operating 100 diagnostic centers in the next five years.
“We’re trying to build four diagnostic centers [by early next year] and show that the new centers will have the same trajectory as our first,” Soga says. “After we’ve proven that, we can start building for scale, building maybe two or three centers a month all over Africa, the idea being we know exactly how things will go when you build them.”
A desperate situation
Soga’s father runs a private medical practice in Ikare-Akoko, Nigeria. Like many doctors in rural areas of sub-Saharan Africa, he has long struggled to get reliable medical equipment at affordable prices. Negotiating to purchase used equipment from Europe or China requires expertise in the global equipment marketplace and also comes with risks, as most secondhand equipment lacks warranties and operating manuals.
Genevieve, on the other hand, worked on public health initiatives in Malawi, Ghana, and Uganda before coming to MIT. During those experiences, she realized how useless donated medical equipment is without technicians trained to set up and maintain them, and without access to spare parts.
“Countless times I saw rooms full of equipment that had never been set up or equipment that had been used for a few months before breaking down, with no hope of repair,” she says.
A common goal
Soga entered MIT’s system design and management graduate program in 2014 and met Genevieve later that year. The two quickly realized they shared a passion for improving health care in Africa. For their second date, Soga invited Genevieve to his development ventures class, where he pitched a rough idea for providing rural doctors like his father with high-quality, refurbished medical equipment and ongoing service support.
MIT offered Soga and Genevieve seed funding to further pursue the idea through the Legatum Center, the PKG Center, MIT IDEAS, and the Africa Business Club.
McCord joined the team in the summer of 2016, and the co-founders were able to secure a partnership with Coast 2 Coast Medical in Massachusetts to begin buying refurbished medical equipment in bulk.
But when they began selling the equipment in Nigeria, they realized their biggest customers were from hospitals and clinics in big cities that predominantly served high-income patients. These facilities already had access to many of the machines MDaaS was selling, but found they could save money through the startup.
The founders faced a dilemma: They weren’t serving the people that needed them most, the low-income communities they’d dreamed of helping since their time in Africa, and yet, by the summer of 2017, the business was profitable — a difficult milestone for startups anywhere, let alone one in Nigeria. They tried different financing options to get their equipment to poorer clinics, including offering to lease or rent out the equipment, but clinics in rural and low-income areas still struggled to achieve the patient volumes necessary to make it work.
“We weren’t reaching this really large market, the 130 million patients that live outside of the largest urban areas that have the biggest issues accessing medical equipment,” Soga says. “The market of high-end hospitals wasn’t exciting for us. … We’d be stuck in big cities, serving high-end clientele. That wasn’t what drove us.”
Upending their business model, they decided to take on new costs and open their own diagnostic center in a low-income community in southwestern Nigeria. The people in this community had limited access to the high-quality diagnostic services enabled by the company’s machines. By centralizing diagnostic services, the founders could aggregate patient demand across dozens of hospitals and clinics, helping them keep prices low and scale faster than if they just sold equipment. This approach would also give the founders a chance to work directly with the patients they were trying to help.
Even as they faced bigger challenges and risks associated with the new model, they never planned to stop at one clinic.
“We had to make the change,” Soga says. “We just kept following our north star, which is to improve health care outcomes. Anybody can build one clinic, but it gets really interesting when you’re building 20, 30, 40 clinics across the continent.”
The MDaaS clinic has been up and running since November 2017. It features a digital X-ray machine, an electrocardiogram (ECG), an electroencephalogram (EEG), an ultrasound, and a full suite lab. For most tests, in-house physicians interpret the results. For others, results are sent to specialized clinicians in big cities.
Today, MDaaS gets patient referrals from more than 60 hospitals and clinics in the region in addition to welcoming walk-ins and partnering with insurance companies. About 70 percent of the people MDaaS treats are women and children.
The founders say they broke even on their operations in just five months and have been operating profitably ever since, proving the need for their services in the area. In fact, the number of patients seen per day at the center has grown by a factor of five since January 2018.
Their dream of operating 100 diagnostic centers will begin by building a few more in Nigeria before they expand to nearby countries, including Ghana and Cote D’Ivoire, possibly as early as next year.
“Right now, we want to test replicating what we have and learn how to manage multiple facilities at once,” Soga says.
As for Genevieve’s mounting phone notifications, she remains thrilled to get constant reminders of the impact the co-founders’ hard work is having. Still, with the ultimate goal of transforming care across sub-Saharan Africa, she admits she’ll have to turn them off at some point soon.
“We’re trying to get to the point where it’s almost a diagnostic center in a box,” she says. “We can provide everything you’d need to go from zero patients to seeing 1,000 or 2,000 a month. We’re also getting so much data and information about the people we’re seeing, so we know the diseases they’re coming in for and the type of diagnostics they need. This information will become increasingly important as we look to build health care solutions for hundreds of thousands of patients instead of tens of thousands.”
Seven MIT faculty members were among the more than 300 recipients of the 2019 Presidential Early Career Awards for Scientists and Engineers (PECASE), the highest honor bestowed by the U.S. government to science and engineering professionals in the early stages of their independent research careers.
Those from MIT who were honored were:
- Joseph Checkelsky, assistant professor in the Department of Physics;
- Kwanghun Chung, associate professor in the departments of Brain and Cognitive Sciences and Chemical Engineering
- James M. LeBeau, the John Chipman Associate Professor of Materials Science and Engineering;
- Yen-Jie Lee, the Class of 1958 Career Development Associate Professor in the Department of Physics;
- Benedetto Marelli, the Paul M. Cook Career Development Assistant Professor in the Department of Civil and Environmental Engineering;
- Tracy Slatyer, the Jerrold R. Zacharias Career Development Associate Professor of Physics; and
- Yogesh Surendranath, the Paul M. Cook Career Development Assistant Professor in the Department of Chemistry.
All of the 2019 MIT recipients were employed or funded by the following U.S. departments and agencies: Department of Defense, Department of Energy, and the Department of Health and Human Services.
These departments and agencies annually nominate the most meritorious scientists and engineers whose early accomplishments show exceptional promise for leadership in science and engineering and contributing to the awarding agencies' missions.
Established by President Bill Clinton in 1996, the PECASE awards are coordinated by the Office of Science and Technology Policy within the Executive Office of the President. Awardees are selected for their pursuit of innovative research at the frontiers of science and technology and their commitment to community service as demonstrated through scientific leadership, public education, or community outreach.
Over the next decade, the biggest generator of data is expected to be devices which sense and control the physical world. From autonomy to robotics to smart cities, this data explosion — paired with advances in machine learning — creates new possibilities for designing and optimizing technological systems that use their own real-time generated data to make decisions.
To address the many scientific questions and application challenges posed by the real-time physical processes of these "dynamical" systems, researchers from MIT and elsewhere organized a new annual conference called Learning for Dynamics and Control. Dubbed L4DC, the inaugural conference was hosted at MIT by the Institute for Data, Systems, and Society (IDSS).
As excitement has built around machine learning and autonomy, there is an increasing need to consider both the data that physical systems produce and feedback these systems receive, especially from their interactions with humans. That extends into the domains of data science, control theory, decision theory, and optimization.
“We decided to launch L4DC because we felt the need to bring together the communities of machine learning, robotics, and systems and control theory,” said IDSS Associate Director Ali Jadbabaie, a conference co-organizer and professor in IDSS, the Department of Civil and Environmental Engineering (CEE), and the Laboratory for Information and Decision Systems (LIDS).
“The goal was to bring together these researchers because they all converged on a very similar set of research problems and challenges,” added co-organizer Ben Recht, of the University of California at Berkeley, in opening remarks.
Over the two days of the conference, talks covered core topics from the foundations of learning of dynamics models, data-driven optimization for dynamical models and optimization for machine learning, reinforcement learning for physical systems, and reinforcement learning for both dynamical and control systems. Talks also featured examples of applications in fields like robotics, autonomy, and transportation systems.
“How could self-driving cars change urban systems?” asked Cathy Wu, an assistant professor in CEE, IDSS, and LIDS, in a talk that investigated how transportation and urban systems may change over the next few decades. Only a small percentage of autonomous vehicles are needed to significantly affect traffic systems, Wu argued, which will in turn affect other urban systems. “Distribution learning provides us with an understanding for integrating autonomy into urban systems,” said Wu.
Claire Tomlin of UC Berkeley presented on integrating learning into control in the context of safety in robotics. Tomlin’s team integrates learning mechanisms that help robots adapt to sudden changes, such as a gust of wind, an unexpected human behavior, or an unknown environment. “We’ve been working on a number of mechanisms for doing this computation in real time,” Tomlin said.
Pablo Parillo, a professor in the Department of Electrical Engineering and Computer Science and faculty member of both IDSS and LIDS, was also a conference organizer, along with George Pappas of the University of Pennsylvania and Melanie Zellinger of ETH Zurich.
L4DC was sponsored by the National Science Foundation, the U.S. Air Force Office of Scientific Research, the Office of Naval Research, and the Army Research Office, a part of the Combat Capabilities Development Command Army Research Laboratory (CCDC ARL).
"The cutting-edge combination of classical control with recent advances in artificial intelligence and machine learning will have significant and broad potential impact on Army multi-domain operations, and include a variety of systems that will incorporate autonomy, decision-making and reasoning, networking, and human-machine collaboration," said Brian Sadler, senior scientist for intelligent systems, U.S. Army CCDC ARL.
Organizers plan to make L4DC a recurring conference, hosted at different institutions. “Everyone we invited to speak accepted,” Jadbabaie said. “The largest room in Stata was packed until the end of the conference. We take this as a testament to the growing interest in this area, and hope to grow and expand the conference further in the coming years.”
MIT granted tenure to eight School of Science faculty members in the departments of Biology; Chemistry; Earth, Atmospheric and Planetary Sciences; Mathematics; and Physics.
William Detmold’s research within the area of theoretical particle and nuclear physics incorporates analytical methods, as well as the power of the world’s largest supercomputers, to understand the structure, dynamics, and interactions of particles like protons and to look for evidence of new physical laws at the sub-femtometer scale probed in experiments such as those at the Large Hadron Collider. He joined the Department of Physics in 2012 from the College of William and Mary, where he was an assistant professor. Prior to that, he was a research assistant professor at the University of Washington. He received his BS and PhD from the University of Adelaide in Australia in 1996 and 2002, respectively. Detmold is a researcher in the Center for Theoretical Physics in the Laboratory for Nuclear Science.
Semyon Dyatlov explores scattering theory, quantum chaos, and general relativity by employing microlocal analytical and dynamical system methods. He came to the Department of Mathematics as a research fellow in 2013 and became an assistant professor in 2015. He completed his doctorate in mathematics at the University of California at Berkeley in 2013 after receiving a BS in mathematics at Novosibirsk State University in Russia in 2008. Dyatlov spent time after finishing his PhD as a postdoc at the Mathematical Sciences Research Institute before moving to MIT.
Mary Gehring studies plant epigenetics. By using a combination of genetic, genomic, and molecular biology, she explores how plants inherit and interpret information that is not encoded in their DNA to better understand plant growth and development. Her lab focuses primarily on Arabidopsis thaliana, a small flowering plant that is a model species for plant research. Gehring joined the Department of Biology in 2010 after performing postdoctoral research at the Fred Hutchinson Cancer Research Center. She received her BA in biology from Williams College in 1998 and her doctorate from the University of California at Berkeley in 2005. She is also a member of the Whitehead Institute for Biomedical Research.
David McGee performs research in the field of paleoclimate, merging information from stalagmites, lake deposits, and marine sediments with insights from models and theory to understand how precipitation patterns and atmospheric circulation varied in the past. He came to MIT in 2012, joining the Department of Earth, Atmospheric and Planetary Sciences after completing a NOAA Climate and Global Change Postdoctoral Fellowship at the University of Minnesota. Before that, he attended Carleton College for his BA in geology in 1993-97, Chatham College for an MA in teaching from 1999 to 2003, Tulane University for his MS from 2004 to 2006, and Columbia University for his PhD from 2006 to 2009. McGee is the director of the MIT Terrascope First-Year Learning Community, a role he has held for the past four years.
Ankur Moitra works at the interface between theoretical computer science and machine learning by developing algorithms with provable guarantees and foundations for reasoning about their behavior. He joined the Department of Mathematics in 2013. Prior to that, he received his BS in electrical and computer engineering from Cornell University in 2007, and his MS and PhD in computer science from MIT in 2009 and 2011, respectively. He was a National Science Foundation postdoc at the Institute for Advanced Study until 2013. Moitra was a 2018 recipient of a School of Science Teaching Prize. He is also a principal investigator in the Computer Science and Artificial Intelligence Laboratory (CSAIL) and a core member of the Center for Statistics.
Matthew Shoulders focuses on integrating biology and chemistry to understand how proteins function in the cellular setting, including proteins’ shape, quantity, and location within the body. This research area has important implications for genetic disorders and neurodegenerative diseases such as Alzheimer’s, diabetes, cancer, and viral infections. Shoulders’ lab works to elucidate, at the molecular level, how cells solve the protein-folding problem, and then uses that information to identify how diseases can develop and to provide insight into new targets for drug development. Shoulders joined the Department of Chemistry in 2012 after earning a BS in chemistry and minor in biochemistry from Virginia Tech in 2004 and a PhD in chemistry from the University of Wisconsin at Madison in 2009. He is also an associate member of the Broad Institute of MIT and Harvard, and a member of the MIT Center for Environmental Health Sciences.
Tracy Slatyer researches fundamental aspects of theoretical physics, answering questions about both visible and dark matter by searching for potential indications of new physics in astrophysical and cosmological data. She has developed and adapted novel techniques for data analysis, modeling, and calculations in quantum field theory; her work has also inspired a range of experimental investigations. The Department of Physics welcomed Slatyer in 2013 after she completed a three-year postdoctoral fellowship at the Institute for Advanced Study. She majored in theoretical physics as an undergraduate at the Australian National University, receiving a BS in 2005, and completed her PhD in physics at Harvard University in 2010. In 2017, Slatyer received the School of Science Prize in Graduate Teaching and was also named the first recipient of the school’s Future of Science Award. She is a member of the Center for Theoretical Physics in the Laboratory for Nuclear Science.
Michael Williams uses novel experimental methods to improve our knowledge of fundamental particles, including searching for new particles and forces, such as dark matter. He also works on advancing the usage of machine learning within the domain of particle physics research. He joined the Department of Physics in 2012. He previously attended Saint Vincent College as an undergraduate, where he double majored in mathematics and physics. Graduating in 2001, Williams then pursued a doctorate at Carnegie Mellon University, which he completed in 2007. From 2008 to 2012 he was a postdoc at Imperial College London. He is a member of the Laboratory for Nuclear Science.
When it comes to killing cancer cells, two drugs are often better than one. Some drug combinations offer a one-two punch that kills cells more effectively, requires lower doses of each drug, and can help to prevent drug resistance.
MIT biologists have now found that by combining two existing classes of drugs, both of which target cancer cells’ ability to divide, they can dramatically boost the drugs’ killing power. This drug combination also appears to largely spare normal cells, because cancer cells divide differently than healthy cells, the researchers say. They hope a clinical trial of this combination can be started within a year or two.
“This is a combination of one class of drugs that a lot of people are already using, with another type of drug that multiple companies have been developing,” says Michael Yaffe, a David H. Koch Professor of Science and the director of the MIT Center for Precision Cancer Medicine. “I think this opens up the possibility of rapid translation of these findings in patients.”
The discovery was enabled by a new software program the researchers developed, which revealed that one of the drugs had a previously unknown mechanism of action that strongly enhances the effect of the other drug.
Yaffe, who is also a member of the Koch Institute for Integrative Cancer Research, is the senior author of the study, which appears in the July 10 issue of Cell Systems. Koch Institute research scientists Jesse Patterson and Brian Joughin are the first authors of the paper.
Yaffe’s lab has a longstanding interest in analyzing cellular pathways that are active in cancer cells, to find how these pathways work together in signaling networks to create disease-specific vulnerabilities that can be targeted with multiple drugs. When the researchers began this study, they were looking for a drug that would amplify the effects of a type of drug known as a PLK1 inhibitor. Several PLK1 inhibitors, which interfere with cell division, have been developed, and some are now in phase 2 clinical trials.
Based on their previous work, the researchers knew that PLK1 inhibitors also produce a type of DNA and protein damage known as oxidation. They hypothesized that pairing PLK1 inhibitors with a drug that prevents cells from repairing oxidative damage could make them work even better.
To explore that possibility, the researchers tested a PLK1 inhibitor along with a drug called TH588, which blocks MTH1, an enzyme that helps cells counteract oxidative damage. This combination worked extremely well against many types of human cancer cells. In some cases, the researchers could use one-tenth of the original doses of each drug, given together, and achieve the same rates of cell death of either drug given on its own.
“It’s really striking,” Joughin says. “It’s more synergy than you generally see from a rationally designed combination.”
However, they soon realized that this synergy had nothing to do with oxidative damage. When the researchers treated cancer cells missing the gene for MTH1, which they thought was TH588’s target, they found that the drug combination still killed cancer cells at the same high rates.
“Then we were really stuck, because we had a good combination, but we didn’t know why it worked,” Yaffe says.
To solve the mystery, they developed a new software program that allowed them to identify the cellular networks most affected by the drugs. The researchers tested the drug combination in 29 different types of human cancer cells, then fed the data into the software, which compared the results to gene expression data for those cell lines. This allowed them to discover patterns of gene expression that were linked with higher or lower levels of synergy between the two drugs.
This analysis suggested that both drugs were targeting the mitotic spindle, a structure that forms when chromosomes align in the center of a cell as it prepares to divide. Experiments in the lab confirmed that this was correct. The researchers had already known that PLK1 inhibitors target the mitotic spindle, but they were surprised to see that TH588 affected the same structure.
“This combination that we found was very nonobvious,” Yaffe says. “I would never have given two drugs that both targeted the same process and expected anything better than just additive effects.”
“This is an exciting paper for two reasons,” says David Pellman, associate director for basic science at Dana-Farber/Harvard Cancer Center, who was not involved in the study. “First, Yaffe and colleagues make an important advance for the rational design of drug therapy combinations. Second, if you like scientific mysteries, this is a riveting example of molecular sleuthing. A drug that was thought to act in one way is unmasked to work through an entirely different mechanism.”
The researchers found that while both of the drugs they tested disrupt mitosis, they appear to do so in different ways. TH588 binds to microtubules, which form the mitotic spindle, and slows their assembly. Many similar microtubule inhibitors are already used clinically to treat cancer. The researchers showed that some of those microtubule inhibitors also synergize with PLK1 inhibitors, and they believe those would likely be more readily available for rapid use in patients than TH588, the drug they originally tested.
While the PLK1 protein is involved in multiple aspects of cell division and spindle formation, it’s not known exactly how PLK1 inhibitors interfere with the mitotic spindle to produce this synergy. Yaffe said he suspects they may block a motor protein that is necessary for chromosomes to travel along the spindle.
One potential benefit of this drug combination is that the synergistic effects appear to specifically target cancer cell division and not normal cell division. The researchers believe this could be because cancer cells are forced to rely on alternative strategies for cell division because they often have too many or too few chromosomes, a state known as aneuploidy.
“Based on the work we have done, we propose that this drug combination targets something fundamentally different about the way cancer cells divide, such as altered cell division checkpoints, chromosome number and structure, or other structural differences in cancer cells,” Patterson says.
The researchers are now working on identifying biomarkers that could help them to predict which patients would respond best to this drug combination. They are also trying to determine the exact function of PLK1 that is responsible for this synergy, in hopes of finding additional drugs that would block that interaction.
The research was funded by the National Institutes of Health, the Charles and Marjorie Holloway Foundation, the Ovarian Cancer Research Fund, the MIT Center for Precision Cancer Medicine, the Koch Institute Dana Farber/Harvard Cancer Center Bridge Project, an American Cancer Society Postdoctoral Fellowship, the Koch Institute Support (core) Grant from the National Cancer Institute, and the Center for Environmental Health Support Grant.
Economist Daron Acemoglu, whose far-ranging research agenda has produced influential studies about government, innovation, labor, and globalization, has been named Institute Professor, MIT’s highest faculty honor.
Acemoglu is one of two MIT professors earning that distinction in 2019. The other, political scientist Suzanne Berger, has been named the inaugural John M. Deutch Institute Professor.
Acemoglu and Berger join a select group of people holding the Institute Professor title at MIT. There are now 12 Institute Professors, along with 11 Institute Professors Emeriti. The new appointees are the first faculty members to be named Institute Professors since 2015.
“As an Institute Professor, Daron Acemoglu embodies the essence of MIT: boldness, rigor and real-world impact,” says MIT President L. Rafael Reif. “From the John Bates Clark Medal to his decades of pioneering contributions to the literature, Daron has built an exceptional record of academic accomplishment. And because he has focused his creativity on broad, deep questions around the practical fate of nations, communities and workers, his work will be essential to making a better world in our time.”
In a letter sent to the MIT faculty today, MIT Provost Martin A. Schmidt and MIT Chair of the Faculty Susan Silbey noted that the honor recognizes “exceptional distinction by a combination of leadership, accomplishment, and service in the scholarly, educational, and general intellectual life of the Institute and wider community.” Schmidt and Silbey also cited Acemoglu’s “significant impacts in diverse fields of economics” and praised him as “one of the most dedicated teachers and mentors in his department.”
Nominations for faculty to be promoted to the rank of Institute Professor may be made at any time, by any member of the faculty, and should be directed to MIT’s Chair of the Faculty.
A highly productive scholar with broad portfolio of research interests, Acemoglu has spent more than 25 years at MIT examining complicated, large-scale economic questions — and producing important answers.
“I’m greatly honored,” he says. “I’ve spent all my career at MIT, and this is a recognition that makes me humbled and happy.”
At different times in his career, Acemoglu has published significant research on topics ranging from labor economics to network effects within economies. However, his most prominent work in the public sphere examines the dynamics of political institutions, democracy, and economic growth.
Working with colleagues, Acemoglu has built an extensive empirical case that the existence of government institutions granting significant rights for individuals has spurred greater economic activity over the last several hundred years. At the same time, he has also produced theoretical work modeling political changes in many countries.
He has researched the relationship between institutions and economics most extensively with political scientist James Robinson at the University of Chicago, as well as with Simon Johnson of the MIT Sloan School of Management. However, he has published papers about political dynamics with many other scholars as well.
Acemoglu has also been keenly interested in other issues during the course of his career. In labor economics, Acemoglu’s work has helped account for the wage gap between higher-skill and lower-skill workers; he has also shown why firms benefit from investing in improving employee skills, even if those workers might leave or require higher wages.
In multiple papers over the last decade, Acemoglu has also examined the labor-market implications of automation, robotics, and AI. Using both theoretical and empirical approaches, Acemoglu has shown how these technologies can reduce employment and wages unless accompanied by other, counterbalancing innovations that increase labor productivity.
In still another area of recent work, Acemoglu has shown how economic shocks within particular industrial sectors can produce cascading effects that propagate through an entire economy, work that has helped economists re-evaluate ideas about the aggregate performance of economies.
Acemoglu credits the intellectual ethos at MIT and the environment created by his colleagues as beneficial to his own research.
“MIT is a very down-to-earth, scientific, no-nonsense environment, and the economics department here has been very open-minded, in an age when economics is more relevant than ever but also in the midst of a deep transformation,” he says. “I think it’s great to have an institution, and colleagues, open to new ideas and new things.”
Acemoglu has authored or co-authored over 120 (and still rapidly counting) peer-reviewed papers. His fifth book, “The Narrow Corridor,” co-authored with Robinson, will be published in September. It takes a global look at the development of, and pressures on, individual rights and liberties. He has advised over 60 PhD students at MIT and is known for investing considerable time reading the work of his colleagues.
As a student, Acemoglu received his BA from the University of York, and his MSc and PhD from the London School of Economics, the latter in 1992. His first faculty appointment was at MIT in 1993, and he has been at the Institute ever since. He was promoted to full professor in 2000, and since 2010 has been the Elizabeth and James Killian Professor of Economics.
Among Acemoglu’s honors, in 2005 he won the John Bates Clark Medal, awarded by the American Economic Association to the best economist under age 40. Acemoglu has also won the Nemmers Prize in Economics, the BBVA Foundation Frontiers of Knowledge Award, and been elected to the National Academy of Sciences. This month, Acemoglu also received the Global Economy Prize 2019, from the Institute for the World Economy.
Political scientist Suzanne Berger has been named MIT’s inaugural John M. Deutch Institute Professor, joining the select group of people holding MIT’s highest faculty honor.
Berger is a lauded scholar who has published many studies of European politics and society, and who, in an overlapping phase of her career, has become an influential expert about the prospects of America’s innovation economy and advanced manufacturing.
Along with Berger, economist Daron Acemoglu has also been named Institute Professor. There are now 12 faculty holding the Institute Professor title, along with 11 Institute Professors Emeriti. The new appointees are the first faculty members to be named Institute Professors since 2015.
“It is difficult to imagine anyone more deserving of the distinction of Institute Professor than Suzanne Berger,” says MIT President L. Rafael Reif. “Throughout her one-of-a-kind career, Suzanne has worked at the frontier of at least three distinct research areas and made influential contributions in every one. She stepped forward to inspire and lead groundbreaking research collaborations that brilliantly served both MIT and the nation. And — before we knew how much we needed it — she had the wisdom to invent the signature program that now leads MIT students into deep engagement with cultures around the world.”
In a letter sent to MIT faculty today, MIT Provost Martin A. Schmidt and MIT Chair of the Faculty Susan Silbey lauded Berger as an “internationally acclaimed scholar” and praised her work on numerous campus-wide MIT initiatives.
Berger’s central role in multiple MIT studies of the innovation economy and global business competition has “helped MIT in the realization of its mission to ‘serve the nation and the world,’” Schmidt and Silbey wrote. They added that Berger, as founding director of the MIT International Science and Technology Initiatives (MISTI), “has had a profound impact on generations of MIT students.”
MISTI sends hundreds of MIT students a year to internships in overseas labs and companies, and funds MIT faculty collaborations with researchers globally.
Nominations for faculty to be promoted to the rank of Institute Professor may be made at any time, by any member of the faculty, and should be directed to MIT’s Chair of the Faculty.
In a sense, Berger has almost packed two careers into her time at MIT. When Berger joined MIT in 1968, she was studying the political ideologies of French peasants, and she has published multiple books and articles about French and European society and politics, including “Peasants Against Politics,” (1972), “The French Political System,” (1974), and “Dualism and Discontinuity in Industrial Societies,” (1980), the latter co-authored with Michael Piore.
Additionally, starting in the 1980s, Berger became a key figure in several MIT-wide study projects, a branching interest that Berger credits in part to the broad-ranging research environment at MIT.
“MIT really changed me,” Berger says. “I’ve learned a lot at MIT. What an extraordinary place to be constantly learning, and rethinking your basic assumptions about how the world works.”
Berger adds that she “deeply honored” to be named an Institute Professor, and noted that outside of MIT, “many people do not understand that we have extraordinary departments in economics, political science, linguistics, philosophy, and more. So on behalf of those of us on social sciences, I feel this is recognition of the role social scientists play, both in research and in the education of our students.”
As Berger also notes, her career is also marked by both her own individual research, and her participation in Institute initiatives, some of which have been highly influential in shaping public discourse.
“Over all my years at MIT, I’ve come to see that Institute Professors are people who both have worked in their own fields and made contributions to the Institute,” Berger says.
That certainly is true in her case. In 1986, Berger was named to MIT’s Commission on Industrial Productivity, which conducted an intensive multiyear study of U.S. industry. That resulted in the widely read book “Made in America” and spurred MIT to found its Industrial Performance Center.
For Berger’s part, serving on the commission also spurred her to play a central role in subsequent Institute-wide projects. That included studies of Hong Kong and Taiwan, for which she and Richard Lester, now associate provost at MIT overseeing international activities, co-edited the books “Made By Hong Kong” (1997) and “Global Taiwan” (2005).
More recently, Berger was a key part of a five-year Institute global study of manufacturing that resulted in a 2006 book she authored, “How We Compete.” The book evaluated the strategies of multinational companies, examining when they outsource tasks to other firms and under what circumstances they move their own operations overseas.
Berger followed that up by co-chairing MIT’s commission on Production in the Innovation Economy, formed in 2010, which took a deep look at the state of advanced manufacturing in the U.S., providing important input for federal policy in this area. Berger was also lead author of a 2013 book written with the other commission members, “Making in America,” summarizing the group’s findings.
Currently Berger’s work is continuing along two tracks. She is a member of MIT’s “Work of the Future” task force, which is studying the condition of labor in the U.S., and working to complete a book project of her own, on the wave of globalization that occurred in the late 19th century.
Berger received her undergraduate degree from the University of Chicago and her PhD from Harvard University in 1967. She joined the MIT faculty in 1968 and has been at the Institute ever since.
Berger has received many other honors in her career. She was made a Chevalier de la Légion d’Honneur by France in 2009. She has also been awarded a Guggenheim fellowship, and been named a fellow of the American Academy of Arts and Sciences.
Lisa Volpatti loves helping people. She also loves a challenge. That’s part of the reason why she’s working to improve insulin therapies for diabetic patients.
A PhD student in chemical engineering, Volpatti is researching avenues for a self-regulating insulin treatment that people with diabetes could take once a day. The insulin would be released from an implanted reservoir when a person’s blood sugar levels are high. Manual insulin administration doesn’t always mimic the function of a healthy pancreas, and it’s a burden for patients to give themselves regular injections. Volpatti hopes a self-regulating insulin system could help keep patients’ blood sugar at therapeutic levels for longer periods of time.
One in 11 people across the globe have diabetes, and so the potential reach of Volpatti’s research is massive.
“I get really excited about working on something that could potentially help so many people across the globe and give them a higher quality of life,” she says. “And it’s a really challenging problem, so that’s also exciting from a scientific standpoint.”
Dispelling imposter syndrome
Before coming to MIT, Volpatti studied chemical engineering at the University of Pittsburgh. During her senior year, she applied to the graduate program in MIT’s Department of Chemical Engineering (ChemE). She didn’t get in, but that didn’t dissuade her from trying a second time. After going abroad and earning a master’s degree in chemistry from Cambridge University, Volpatti applied to MIT again and was accepted.
“I was really embarrassed to share that with people because I felt like I didn’t really belong. But now, I think that I’ve had a lot of success here, and I’m more willing to share that with people who are also struggling with imposter syndrome, or who think that they can’t do it, or that if they get a rejection it’s the end. It’s never the end,” Volpatti says.
At Cambridge University, her research involved looking at amyloid fibrils, proteins that are typically associated with neurodegenerative disorders, and investigating possible uses for them in biotechnology, specifically in drug delivery. As a fifth-year doctoral student at MIT, working in the labs of Daniel Anderson and Robert Langer, Volpatti continues to work with drug-delivery applications, now for insulin therapies.
Caring for her community
Volpatti’s passion for helping others is reflected in her community service at the Institute, especially in the department where she makes her academic home.
“It’s always been my goal, broadly, to help people. Since I was really excited about chemistry, I thought medicine would be a great place to do that. Throughout my undergrad and grad careers, I try to be involved in other things [in addition to academics] so I can give back, because I also have gotten a lot of help,” explains Volpatti.
She is the co-founder of the Institute’s Graduate Women in Chemical Engineering group that provides support for female graduate students in the department. The group is relatively new — it was established last fall — and Volpatti is excited to see where the initiative will go. When the Department of Chemical Engineering received a 2019 Change-maker award for this effort, they asked Volpatti to accept the award on the department’s behalf. She also recently received a 2019 PKG award.
“I’ve had a lot of really important mentors that have helped me make my decisions, so I try to be a mentor for other people as well,” she says.
Volpatti is also a fellow in the ChemE Communication Lab, where she helps students and postdocs with their communication needs. From dissertation help to resume workshopping, Volpatti tries to help her peers effectively translate their work outside of the department.
She is also active in Resources for Easing Friction and Stress (REFS), a confidential peer-to-peer counseling service that serves as a mental health resource for graduate students. In addition to being a peer counselor, Volpatti and her colleagues organize stress-reducing activities such as free ice cream events and mindfulness workshops.
“Anyone can learn”
Volpatti and her colleagues haven’t created the perfect self-regulating insulin system quite yet, but they have made good progress. For example, they have made headway in the kinetics of insulin release. In mouse models, they have minimized the lag in the self-regulating insulin’s response to high glucose levels.
She will finish her degree in December, and will pursue a postdoc in immunology, specifically in cancer immunotherapy, which involves similar materials and delivery principles as her work with insulin, but with a focus on the immune system.
To take a break from her research, Volpatti loves taking runs down to the esplanade along the Charles River. She also enjoys hiking and camping, and staying in touch with her family. She video-chats with her sister and niece on a daily basis, often showing them her experiments in the lab.
Something that not many people know about Volpatti is that she is an adept juggler — a skill she acquired with her signature determination and persistence.
“One summer I just practiced with a friend who knew how and finally figured it out. I now believe that anyone can learn how to juggle,” she says. “You think ‘no I can’t, I’m not coordinated enough’ but you can. Anyone can learn.”
Professor Anne White, head of the Department of Nuclear Science and Engineering (NSE), has announced the appointment of Professor Benoit Forget as associate department head.
The MIT Computational Reactor Physics Group — which Forget leads with Professor Kord Smith — focuses on developing new ways of streamlining the complex software needed to simulate the vast numbers of random interactions that take place inside a nuclear reactor core, in order to better understand how to develop new generations of improved reactor architectures.
Forget earned a BS in chemical engineering and an MS in energy engineering at the École Polytechnique de Montréal. He completed his PhD in nuclear engineering at Georgia Tech in 2006, after which he spent a year and a half working at Idaho National Laboratory before accepting an appointment at MIT.
As associate head, Professor Forget will focus on expanding computational science and engineering activities within NSE, including leading NSE engagement with the new MIT Stephen A. Schwarzman College of Computing. He currently serves as co-chair of the Working Group on College Infrastructure for the MIT Schwarzman College of Computing, which is charged with examining how to ensure that departments, labs, and centers have the information and resources they require to meet their computational needs, such as accessing and storing data.
Forget replaces Professor Jacopo Buongiorno, who served as associate department head and led academic organization and oversight in NSE from 2015 through June 2019.
A graduate student researching red blood cell production, another studying alternative aviation fuels, and an MBA candidate: What do they have in common? They all enrolled in 6.883/6.S083 (Modeling with Machine Learning: From Algorithms to Applications) in spring 2019. The class, offered for the first time during that term, focused on machine learning applications in engineering and the sciences, attracting students from fields ranging from biology to business to architecture.
Among them was Thalita Berpan, who was in her last term before graduating from the MIT Sloan School of Management in June. Berpan previously worked in asset management, where she observed how financial companies increasingly focus on machine learning and related technologies. “I wanted to come to business school to dive into emerging technology and get exposure to all of it,” says Berpan, who has also taken courses on blockchain and robotics. “I thought; ‘Why not take the class so I can understand the building blocks?’”
The class provided Berpan with a thorough grounding in the basics — and more. “Not only do you understand the fundamentals of machine learning, but you actually know how to use them and apply them,” she says. “It’s very satisfying to know how to build machine learning algorithms myself and know what they mean.”
Berpan plans to use what she has learned about data and algorithms to work with design engineers in her post-graduation job in project management. “What are some of the ways that engineers and data scientists can leverage a data set? For me to be able to help guide them through that process is going to be extremely useful,” she says.
Open to both undergraduate and graduate students, 6.883/6.S083 enrolled 66 students for credit in its debut semester. It was created as an experimental alternative to 6.036 (Introduction to Machine Learning), a course that professors Regina Barzilay and Tommi Jaakkola developed and initially taught, and which has become one of the most popular on campus since its introduction in 2013.
Having received feedback that 6.036 was too specialized for some non-electrical engineering and computer science (EECS) majors, Barzilay and Jaakkola designed 6.883/6.S083 to focus on different applications of machine learning. For example, Berpan, along with students from the Department of Biology and the Department of Aeronautics and Astronautics, worked on a group project that used machine learning to predict the accuracy of DNA repair in the CRISPR/Cas9 genome-editing system.
“It doesn’t necessarily mean that the class is easier. It just has a different emphasis,” says Barzilay, the Delta Electronics Professor of Electrical Engineering and Computer Science. “Our goal was to provide the students with a set of tools that would enable them to solve problems in their respective areas of specialization.”
The class includes live lectures that focus on modeling and online materials for building a shared background in machine learning methods, including tutorials for students who have less prior exposure to the subject. “We wanted to help students learn how to model and predict, and understand when they succeeded — skills that are increasingly needed across the Institute,” says Jaakkola, the Thomas Siebel Professor in EECS and the Institute for Data, Systems, and Society (IDSS).
In fact, about two-thirds of those enrolled for spring term were non-EECS majors. “We had a surprising number of people from the MIT School of Architecture and Planning. That’s very exciting,” Jaakkola says.
Ultimately, the instructors say, the new course was built to bring a variety of students together to study an exciting, fast-growing area. “They constantly hear about the wonders of AI, and this enables them to become part of it,” says Barzilay. “Obviously, it brings challenges, too, because they are now in totally new, uncharted territory. But I think they are learning a lot about their abilities to expand to new areas.”
Melissa Nobles, the Kenan Sahin Dean of MIT's School of Humanities, Arts, and Social Sciences, has announced that David Singer is the new head of the Department of Political Science.
Singer is a scholar of international political economy, a subfield of political science focused on international economic relations. He is the author of "Regulating Capital: Setting Standards for the International Financial System" (Cornell University Press, 2007) and co-author, with Mark Copelovitch, of "Banks on the Brink: Global Capital, Securities Markets, and the Political Roots of Financial Crises" (Cambridge University Press, forthcoming).
“David’s well-deserved reputation for dedication and integrity, as well as his research and teaching focus, and his depth of experience in Institute affairs make him remarkably well-suited for this new leadership role,” Nobles says.
Singer says, "I am delighted to be appointed head of the political science department. This is an exhilarating time for MIT, and for political science in particular, as we navigate an evolving intellectual landscape. The computation and big-data revolution poses opportunities and challenges for the discipline, and has been a topic of spirited discussion in the department. Meanwhile, we remain committed to a number of exciting research areas: the dynamics of elections, political accountability, lobbying, and public opinion; the causes of conflict, terrorism, and nuclear proliferation; the evolution of institutions; and the development of new tools for causal inference, to name just a few."
Singer joined the MIT faculty in 2006, following an assistant professorship at the University of Notre Dame. His research interests include the politics of financial regulation, migration, central banking, and global capital markets. He has lectured throughout the world on these topics, with sponsorship by the U.S. State Department, MIT's Industrial Liaison Program, and leading research universities and national central banks. He was a visiting scholar at the American Academy of Arts and Sciences and Harvard's Weatherhead Center, and a visiting professor at Singapore University of Technology and Design. He currently sits on the board of directors of the International Political Economy Society.
Singer is also the incoming secretary of the faculty, the latest role in a long history of service to MIT. He was the inaugural chair of the Committee on Sexual Misconduct Prevention and Response, for which he received a Change Maker Award in 2017. He also served on the Committee on Student Life, the Committee on Distinguished Fellowships, the Medical Consumers' Advisory Council, and the Rainbow Compass LGBTQ Mentorship program. He is currently associate head of MacGregor House, an undergraduate residence hall, where he has lived since 2007.
Fulfilling the ultimate goal of the 2015 Paris Agreement on climate change — keeping global warming well below 2 degrees Celsius, if not 1.5 C — will be impossible without dramatic action from the world’s largest emitter of greenhouse gases, China. Toward that end, China began in 2017 developing an emissions trading scheme (ETS), a national carbon dioxide market designed to enable the country to meet its initial Paris pledge with the greatest efficiency and at the lowest possible cost. China’s pledge, or nationally determined contribution (NDC), is to reduce its CO2 intensity of gross domestic product (emissions produced per unit of economic activity) by 60 to 65 percent in 2030 relative to 2005, and to peak CO2 emissions around 2030.
When it’s rolled out, China’s carbon market will initially cover the electric power sector (which currently produces more than 3 billion tons of CO2) and likely set CO2 emissions intensity targets (e.g., grams of CO2 per kilowatt hour) to ensure that its short-term NDC is fulfilled. But to help the world achieve the long-term 2 C and 1.5 C Paris goals, China will need to continually decrease these targets over the course of the century.
A new study of China’s long-term power generation mix under the nation’s ETS projects that until 2065, renewable energy sources will likely expand to meet these targets; after that, carbon capture and storage (CCS) could be deployed to meet the more stringent targets that follow. Led by researchers at the MIT Joint Program on the Science and Policy of Global Change, the study appears in the journal Energy Economics.
“This research provides insight into the level of carbon prices and mix of generation technologies needed for China to meet different CO2 intensity targets for the electric power sector,” says Jennifer Morris, lead author of the study and a research scientist at the MIT Joint Program. ”We find that coal CCS has the potential to play an important role in the second half of the century, as part of a portfolio that also includes renewables and possibly nuclear power.”
To evaluate the impacts of multiple potential ETS pathways — different starting carbon prices and rates of increase — on the deployment of CCS technology, the researchers enhanced the MIT Economic Projection and Policy Analysis (EPPA) model to include the joint program’s latest assessments of the costs of low-carbon power generation technologies in China. Among the technologies included in the model are natural gas, nuclear, wind, solar, coal with CCS, and natural gas with CCS. Assuming that power generation prices are the same across the country for any given technology, the researchers identify different ETS pathways in which CCS could play a key role in lowering the emissions intensity of China’s power sector, particularly for targets consistent with achieving the long-term 2 C and 1.5 C Paris goals by 2100.
The study projects a two-stage transition — first to renewables, and then to coal CCS. The transition from renewables to CCS is driven by two factors. First, at higher levels of penetration, renewables incur increasing costs related to accommodating the intermittency challenges posed by wind and solar. This paves the way for coal CCS. Second, as experience with building and operating CCS technology is gained, CCS costs decrease, allowing the technology to be rapidly deployed at scale after 2065 and replace renewables as the primary power generation technology.
The study shows that carbon prices of $35-40 per ton of CO2 make CCS technologies coupled with coal-based generation cost-competitive against other modes of generation, and that carbon prices higher than $100 per ton of CO2 allow for a significant expansion of CCS.
“Our study is at the aggregate level of the country,” says Sergey Paltsev, deputy director of the joint program. “We recognize that the cost of electricity varies greatly from province to province in China, and hope to include interactions between provinces in our future modeling to provide deeper understanding of regional differences. At the same time, our current results provide useful insights to decision-makers in designing more substantial emissions mitigation pathways.”
Researchers at MIT and Singapore University of Technology (SUTD) have demonstrated a micro ring resonator made of amorphous silicon carbide with the highest quality factor to date. The resonator shows promise to be used as an on-chip photonic light source at the infrared telecom wavelength of 1,550 nanometers.
Ordinary daylight will pass through a window unaltered, in a process called linear transmission, but the same light passing through a prism will split into a rainbow of colors. Similarly in photonic devices, infrared light from a laser can pass through in linear fashion without changing its “color,” but at high intensity, the light can exhibit nonlinear behavior, generating additional colors, or wavelengths. For example, a single yellow laser coupled to a photonic device can generate blue, green, yellow, or orange colors.
Researchers led by MIT Materials Research Laboratory Research Scientist Anuradha M. Agarwal fabricated the amorphous silicon carbide ring resonators, and researchers at SUTD led by Associate Professor Dawn T.H. Tan analyzed the device’s linear and nonlinear properties.
“We are able to show one order of magnitude higher nonlinear effect than measured before in any of the silicon carbide substrates,” Agarwal says.
Quality factor is a measure of how strongly the resonator produces nonlinear effects. “The larger the quality factor, the better the nonlinear effect,” says Tan, who leads the Photonics Devices and Systems Group at SUTD. “So in this case, the quality factor was pretty good. It was actually much better than we expected.”
The findings are described in a paper, featured on the cover of ACS Photonics, by Agarwal, Tan, MIT materials science and engineering graduate student Danhao Ma, and three others in Singapore and Malaysia.
High intensity of light is needed to trigger nonlinear properties for photonic devices, which can be achieved either by ramping up the power of the laser or using a device such as a ring resonator. “A ring allows for that high intensity because it traps the photons for a long time,” Agarwal explains. “More and more photons build up to like a crescendo and that allows for the evaluation of nonlinear optical properties.”
Like a fiber optic cable, which transmits light by wrapping one material that carries the light inside a different material that won’t allow the light to pass through it, the amorphous silicon carbide ring resonator and straight waveguide for carrying the infrared light are surrounded by a layer of silicon oxide that minimizes the amount of light that can escape. The refractive indices of different materials determine how well they work together as the carrier layer and protective outer layer.
“We are trying to create this kind of a fiber optic waveguide on chip,” Agarwal explains. “So it’s like a fiber, but on a chip, and therefore what we need is a core with a high (refractive) index and a cladding with a low index.” Silicon carbide and silicon oxide have a large enough difference in their refractive indices that they work together well as the core and cladding for a waveguide.
The researchers achieved the record quality factor in this study using the plasma enhanced chemical (PECVD) process to deposit the silicon carbide, at a temperature that is compatible with complementary metal-oxide semiconductor (CMOS) silicon chip processing, and developing a method to pattern and etch the silicon carbide ring resonator, which is coupled to a straight waveguide.
MIT graduate student Ma overcame several processing challenges to make the high-quality resonator. When Ma began working on silicon carbide materials for this study about three years ago, there was no existing recipe for how to etch a pattern into the amorphous silicon carbide material when it is deposited on a silicon dioxide substrate. “Silicon carbide is a very rigid and physically and chemically hard material, so, in other words, it’s very difficult for it to be removed or etched,” Ma says.
To deposit and etch the silicon carbide waveguide on silicon oxide, Ma first used electron beam lithography to pattern the waveguides and reactive ion dry etching to remove excess silicon carbide. But his first attempts using a typical polymer-based mask didn’t work because the process removed more of the mask than the silicon carbide. Ma then tried a metal mask, but grain boundaries from the mask carried over to the silicon carbide, leaving behind rough sidewalls in the waveguides. Roughness is undesirable because it increases photon scattering and light loss. To resolve the issue, Ma developed a technique using a silicon dioxide-based mask for the reactive ion etching. During the process development, Ma worked closely with Qingyang Du, an MIT postdoc, and Mark K. Mondol, assistant director of the NanoStructures Laboratory in the MIT Research Laboratory of Electronics.
“We came up with the right type of chemistries in this reaction and controlled the gas flows and the plasma, or, in other words, the details of the processing recipe,” Ma says. “This recipe is really selective to etch silicon carbide compared to silicon dioxide, which made it possible for us to shape the silicon carbide photonic devices and have a smooth waveguide sidewall,” Ma says. The smooth sidewall is critical for maintaining the optical signals in the photonic device, he notes.
The main sources of light loss in these resonators are absorption of photons in the ring material and/or scattering of photons caused by edge roughness of the ring device. “Danhao’s processing yielded smooth sidewalls, which enabled low loss and a high Q (quality) factor resonator,” Agarwal explains.
“The beauty of this silicon carbide material and the technique that we used here in the paper is that the PECVD process of silicon carbide is an inexpensive process, standard in the silicon microelectronics industry,” says Ma, whose research concentration is materials design and engineering for integrated photonics. “Use of the existing microelectronics processes will make the adoption of silicon carbide into the integrated photonic and integrated electronic platforms easier.” The PECVD and reactive dry ion etching processes he used don’t require the lattice matching and other critical demands of epitaxial growth on silicon, and is substrate-agnostic, Ma says.
Tan has studied silicon nitride materials and other CMOS materials for their nonlinearity for several years. “For (amorphous) silicon carbide, you would have a better enhancement when cast as a resonator compared to ultra-silicon-rich nitride, and it also has a higher nonlinear refractive index than stoichiometric silicon nitride, which is prolific in nonlinear optics,” Tan says.
Several kinds of photon absorption known as two-photon and three-photon absorption are typically present in these devices. In this study, Tan says, loss was dominated by three-photon absorption, which is a relatively weak nonlinear loss mechanism, while two-photon absorption, which can be a problem in many crystalline silicon and amorphous silicon materials, was suppressed.
Agarwal and Tan began collaborating while Tan was a visiting scholar at MIT from August 2013 through August 2014. “We were very fortunate to be paired with Professor Tan’s team, and we benefited a great deal from this collaboration, and we continue to collaborate,” Agarwal says. Agarwal’s team previously worked on using silicon carbide in a sensor for harsh environments.
For the current work, the Singapore team measured the additional wavelengths of light generated in the ring resonator — a phenomenon called spectral broadening, which is quantified by a term called Kerr nonlinearity. The researchers found the Kerr nonlinearity of their silicon carbide film to be almost 10 times that of previously reported crystalline and amorphous silicon carbide.
“With this you see a spectral broadening effect, which we can leverage to our advantage because now instead of having just one frequency, we are generating several other frequencies which can provide a super continuum light source,” Agarwal says.
Professor David J. Moss, director of the Centre for Micro-Photonics at Swinburne University of Technology in Australia, who studies photonic materials, says, “This paper presents new results for amorphous silicon carbide as a promising CMOS-compatible platform for nonlinear optics, particularly focused on the important telecommunications window.”
“The achievement of a high Kerr nonlinearity — comparable to crystalline silicon — along with negligible two-photon absorption, together with record high (for silicon carbide) Q factor ring resonators, is an exciting development in the continuing quest for ever-more-efficient platforms for nonlinear optics at 1,550 nanometers,” adds Moss, who was not involved in this research.
Associate Professor Andrea Melloni, who heads the Photonics Devices Group at Politecnico di Milano in Italy, says, “Amorphous SiC (silicon carbide) deposited with PECVD is of great interest. The refractive index is extremely appealing (2.45 is not a common value) because it is high enough to allow large-scale integration, but not as high as silicon, thus minimizing problems associated with the very high index contrast of SOI (silicon-on-insulator) structures.” Melloni, who also did not participate in this research, published a paper last year on Silicon Oxycarbide Photonic Waveguides.
Looking ahead, Ma hopes to make a thicker silicon carbide waveguide for a broader set of applications — for example, creating more wavelengths (multiplexing) within the single waveguide.
“As a first demonstration of what we’ve done together, I think it’s a very promising platform where if we can continue refining the platform and device design, I think we probably would be able to demonstrate very good resonator enhancement because we have demonstrated very good quality factors,” Tan says. “If we wanted to do something like a frequency comb or an optical parametric oscillator, the threshold power becomes a lot smaller if the quality factor is large.”
“If this work can be jointly funded then we can think about making an integrated light source, sensor and detector, so there are a lot of exciting next steps in this,” Agarwal says.
This work was supported by SUTD–MIT International Design Center, the Singapore National Research Foundation, and the Singapore Ministry of Education.
In the brain, when neurons fire off electrical signals to their neighbors, this happens through an “all-or-none” response. The signal only happens once conditions in the cell breach a certain threshold.
Now an MIT researcher has observed a similar phenomenon in a completely different system: Earth’s carbon cycle.
Daniel Rothman, professor of geophysics and co-director of the Lorenz Center in MIT’s Department of Earth, Atmospheric and Planetary Sciences, has found that when the rate at which carbon dioxide enters the oceans pushes past a certain threshold — whether as the result of a sudden burst or a slow, steady influx — the Earth may respond with a runaway cascade of chemical feedbacks, leading to extreme ocean acidification that dramatically amplifies the effects of the original trigger.
This global reflex causes huge changes in the amount of carbon contained in the Earth’s oceans, and geologists can see evidence of these changes in layers of sediments preserved over hundreds of millions of years.
Rothman looked through these geologic records and observed that over the last 540 million years, the ocean’s store of carbon changed abruptly, then recovered, dozens of times in a fashion similar to the abrupt nature of a neuron spike. This “excitation” of the carbon cycle occurred most dramatically near the time of four of the five great mass extinctions in Earth’s history.
Scientists have attributed various triggers to these events, and they have assumed that the changes in ocean carbon that followed were proportional to the initial trigger — for instance, the smaller the trigger, the smaller the environmental fallout.
But Rothman says that’s not the case. It didn’t matter what initially caused the events; for roughly half the disruptions in his database, once they were set in motion, the rate at which carbon increased was essentially the same. Their characteristic rate is likely a property of the carbon cycle itself — not the triggers, because different triggers would operate at different rates.
What does this all have to do with our modern-day climate? Today’s oceans are absorbing carbon about an order of magnitude faster than the worst case in the geologic record — the end-Permian extinction. But humans have only been pumping carbon dioxide into the atmosphere for hundreds of years, versus the tens of thousands of years or more that it took for volcanic eruptions or other disturbances to trigger the great environmental disruptions of the past. Might the modern increase of carbon be too brief to excite a major disruption?
According to Rothman, today we are “at the precipice of excitation,” and if it occurs, the resulting spike — as evidenced through ocean acidification, species die-offs, and more — is likely to be similar to past global catastrophes.
“Once we’re over the threshold, how we got there may not matter,” says Rothman, who is publishing his results this week in the Proceedings of the National Academy of Sciences. “Once you get over it, you’re dealing with how the Earth works, and it goes on its own ride.”
A carbon feedback
In 2017, Rothman made a dire prediction: By the end of this century, the planet is likely to reach a critical threshold, based on the rapid rate at which humans are adding carbon dioxide to the atmosphere. When we cross that threshold, we are likely to set in motion a freight train of consequences, potentially culminating in the Earth’s sixth mass extinction.
Rothman has since sought to better understand this prediction, and more generally, the way in which the carbon cycle responds once it’s pushed past a critical threshold. In the new paper, he has developed a simple mathematical model to represent the carbon cycle in the Earth’s upper ocean and how it might behave when this threshold is crossed.
Scientists know that when carbon dioxide from the atmosphere dissolves in seawater, it not only makes the oceans more acidic, but it also decreases the concentration of carbonate ions. When the carbonate ion concentration falls below a threshold, shells made of calcium carbonate dissolve. Organisms that make them fare poorly in such harsh conditions.
Shells, in addition to protecting marine life, provide a “ballast effect,” weighing organisms down and enabling them to sink to the ocean floor along with detrital organic carbon, effectively removing carbon dioxide from the upper ocean. But in a world of increasing carbon dioxide, fewer calcifying organisms should mean less carbon dioxide is removed.
“It’s a positive feedback,” Rothman says. “More carbon dioxide leads to more carbon dioxide. The question from a mathematical point of view is, is such a feedback enough to render the system unstable?”
“An inexorable rise”
Rothman captured this positive feedback in his new model, which comprises two differential equations that describe interactions between the various chemical constituents in the upper ocean. He then observed how the model responded as he pumped additional carbon dioxide into the system, at different rates and amounts.
He found that no matter the rate at which he added carbon dioxide to an already stable system, the carbon cycle in the upper ocean remained stable. In response to modest perturbations, the carbon cycle would go temporarily out of whack and experience a brief period of mild ocean acidification, but it would always return to its original state rather than oscillating into a new equilibrium.
When he introduced carbon dioxide at greater rates, he found that once the levels crossed a critical threshold, the carbon cycle reacted with a cascade of positive feedbacks that magnified the original trigger, causing the entire system to spike, in the form of severe ocean acidification. The system did, eventually, return to equilibrium, after tens of thousands of years in today’s oceans — an indication that, despite a violent reaction, the carbon cycle will resume its steady state.
This pattern matches the geological record, Rothman found. The characteristic rate exhibited by half his database results from excitations above, but near, the threshold. Environmental disruptions associated with mass extinction are outliers — they represent excitations well beyond the threshold. At least three of those cases may be related to sustained massive volcanism.
“When you go past a threshold, you get a free kick from the system responding by itself,” Rothman explains. “The system is on an inexorable rise. This is what excitability is, and how a neuron works too.”
Although carbon is entering the oceans today at an unprecedented rate, it is doing so over a geologically brief time. Rothman’s model predicts that the two effects cancel: Faster rates bring us closer to the threshold, but shorter durations move us away. Insofar as the threshold is concerned, the modern world is in roughly the same place it was during longer periods of massive volcanism.
In other words, if today’s human-induced emissions cross the threshold and continue beyond it, as Rothman predicts they soon will, the consequences may be just as severe as what the Earth experienced during its previous mass extinctions.
“It’s difficult to know how things will end up given what’s happening today,” Rothman says. “But we’re probably close to a critical threshold. Any spike would reach its maximum after about 10,000 years. Hopefully that would give us time to find a solution.”
“We already know that our CO2-emitting actions will have consequences for many millennia,” says Timothy Lenton, professor of climate change and earth systems science at the University of Exeter. “This study suggests those consequences could be much more dramatic than previously expected. If we push the Earth system too far, then it takes over and determines its own response — past that point there will be little we can do about it.”
This research was supported, in part, by NASA and the National Science Foundation.
MIT.nano has announced that 11 companies have joined the facility’s consortium as founding members. Drawn from a variety of industries, the founding members are leaders in the development of systems, materials, and technologies for government, business, and consumers around the world.
Since MIT.nano’s official opening in October 2018, a significant effort has been underway to prepare the building’s facilities to support nanoscale researchers from departments, labs, and centers across the campus. The formation of the corporate consortium is an important step in this effort, says Vladimir Bulović, the founding faculty director of MIT.nano.
“Although our founding members come from different industries, they join MIT.nano in common cause: to harness the power of nanotechnology in service to humanity’s greatest challenges,” says Bulović, who is also the Fariborz Maseeh (1990) Chair in Emerging Technology. “We’re proud to have this group of visionary companies in the MIT.nano consortium. Their counsel, collaboration, and leadership will help MIT.nano fulfill its potential to build a better world.”
Companies that join the MIT.nano Consortium will help guide technical pursuits at MIT in two ways. First, their expertise in specific industries and global markets makes them invaluable advisors on real-world challenges and how to deliver solutions at scale. Second, as leading suppliers of advanced tools and processes for industry, research, and manufacturing, the member companies will be able to inform the selection of the tool sets and technologies that are installed in MIT.nano to support the interests of its users.
In return, the member companies benefit from an ongoing relationship with MIT.nano. A primary advantage is early awareness of innovative technologies emerging from MIT, such as through MIT.nano seminars and events. Members could translate this awareness into formal research collaborations with faculty, company-specific seminars, support for MIT startups, and other opportunities.
Member companies may also place an employee on campus as a visiting scientist, embedding this individual in a research group as an intellectual home to understand and explore MIT. And consortium members form natural and extensive connections to emerging MIT talent, enhancing their ability to attract and hire graduating students and postdoctoral associates.
Companies who joined the MIT.nano Consortium, or who began the conversation to do so, prior to January 2019 are recognized as founding members. MIT.nano is honored to recognize the following companies as founding members:
- Agilent Technologies, specializing in life sciences, diagnostics, and applied chemical markets. The company provides analytical, clinical, and academic laboratories worldwide with instruments, software, services, consumables, applications, expertise, and workflow solutions with a focus on six key market areas: food, environment and forensics, pharmaceutical, diagnostics, chemical and energy, and research.
- Analog Devices (ADI) is a provider of high-performance analog, mixed-signal, and digital signal processing solutions that bridge the physical and digital domains. More than 100,000 customers worldwide — across an array of industries including instrumentation, automation, communications, health care, and automotive domains — rely on ADI for its portfolio of products and technologies that sense, measure, power, connect, interpret, and secure.
- Dow, a materials science company with technology, asset integration, scale, and competitive capabilities that enable it to address complex global issues. Dow’s portfolio of performance materials, industrial intermediates, and plastics businesses deliver a range of differentiated technology-based products and solutions for customers in high-growth markets such as packaging, infrastructure, and consumer care.
- Draper, a not-for-profit engineering innovation company that focuses on the design, development, and deployment of advanced technological solutions, providing engineering expertise to government, industry, and academia in a myriad of domains including national security, strategic systems, commercial sectors, and space.
- DSM, a global purpose-led, science-based company active in nutrition, health, and sustainable living. DSM delivers innovative solutions for human nutrition, animal nutrition, personal care and aroma, medical devices, green products and applications, and new mobility and connectivity.
- Edwards, with a 100-year history specializing in the design, manufacture, and support of sophisticated vacuum system products, abatement solutions, and related services. Edwards products enable the discovery, development and manufacture of things that leverage the nanoscale, as well as a range of industrial processes, scientific instruments, and R&D applications.
- IBM Research, one of the world’s largest corporate research labs with more than 3,000 researchers in 12 labs located across six continents. IBM Research pioneers promising and disruptive technologies that will transform industries and society, including the future of artificial intelligence, hybrid cloud, and quantum computing.
- Lam Research, an enabler of the semiconductor industry whose wafer fabrication equipment and services allow chipmakers to build smaller, faster, and better-performing electronic devices. Today, nearly every advanced chip is built with Lam technology.
- NCSOFT, one of the largest gaming companies in the world and creator of many of the most prominent multiplayer online video games to date. It engages hundreds of millions of players daily, worldwide, with an extensive portfolio of game franchises such as Lineage, AION, Blade & Soul, and Guild Wars.
- NEC, a global provider of information and communications technology services, integrating IT and network technologies for industry, government, and individual customers through innovative software, applications, development tools, and services.
- Waters, a specialty measurement company, has pioneered chromatography, mass spectrometry, and thermal analysis innovations serving the life, materials, and food sciences for more than 60 years.
“MIT.nano will continue to welcome new companies and other organizations to the consortium, fulfilling its mission to search for a broader understanding of the most pressing issues our community of researchers and discoverers should address,” says Bulović. “Engagement, advice, and collaboration with industry leaders boost MIT.nano's ability to deliver the most pertinent solutions to the world."
For more details, visit the MIT.nano Consortium page.