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Training robots to manipulate soft and deformable objects

Wed, 06/09/2021 - 3:20pm

Robots can solve a Rubik’s cube and navigate the rugged terrain of Mars, but they struggle with simple tasks like rolling out a piece of dough or handling a pair of chopsticks. Even with mountains of data, clear instructions, and extensive training, they have a difficult time with tasks easily picked up by a child.

A new simulation environment, PlasticineLab, is designed to make robot learning more intuitive. By building knowledge of the physical world into the simulator, the researchers hope to make it easier to train robots to manipulate real-world objects and materials that often bend and deform without returning to their original shape. Developed by researchers at MIT, the MIT-IBM Watson AI Lab, and University of California at San Diego, the simulator was launched at the International Conference on Learning Representations in May.

In PlasticineLab, the robot agent learns how to complete a range of given tasks by manipulating various soft objects in simulation. In RollingPin, the goal is to flatten a piece of dough by pressing on it or rolling over it with a pin; in Rope, to wind a rope around a pillar; and in Chopsticks, to pick up a rope and move it to a target location.

The researchers trained their agent to complete these and other tasks faster than agents trained under reinforcement-learning algorithms, they say, by embedding physical knowledge of the world into the simulator, which allowed them to leverage gradient descent-based optimization techniques to find the best solution.  

“Programming a basic knowledge of physics into the simulator makes the learning process more efficient,” says the study’s lead author, Zhiao Huang, a former MIT-IBM Watson AI Lab intern who is now a PhD student at the University of California at San Diego. “This gives the robot a more intuitive sense of the real world, which is full of living things and deformable objects.”

“It can take thousands of iterations for a robot to master a task through the trial-and-error technique of reinforcement learning, which is commonly used to train robots in simulation,” says the work’s senior author, Chuang Gan, a researcher at IBM. “We show it can be done much faster by baking in some knowledge of physics, which allows the robot to use gradient-based planning algorithms to learn.”

Basic physics equations are baked in to PlasticineLab through a graphics programming language called Taichi. Both TaiChi and an earlier simulator that PlasticineLab is built on, ChainQueen, were developed by study co-author Yuanming Hu SM '19, PhD '21. Through the use of gradient-based planning algorithms, the agent in PlasticineLab is able to continuously compare its goal against the movements it has made to that point, leading to faster course-corrections.

“We can find the optimal solution through back propagation, the same technique used to train neural networks,” says study co-author Tao Du, a PhD student at MIT. “Back propagation gives the agent the feedback it needs to update its actions to reach its goal more quickly.”

The work is part of an ongoing effort to endow robots with more common sense so that they one day might be capable of cooking, cleaning, folding the laundry, and performing other mundane tasks in the real world.

Other authors of PlasticineLab are Siyuan Zhou of Peking University, Hao Su of UCSD, and MIT Professor Joshua Tenenbaum.

STEM + humanities = a framework for understanding the world

Wed, 06/09/2021 - 1:50pm

When Natasha Joglekar ’21 faced some serious medical issues back in fall 2018, and was feeling ill and isolated, she found particular comfort in one class that term: WGS.229 (Race, Culture, and Gender in the U.S. and Beyond: A Psychological Perspective). “I think that class was sometimes the only time I talked to people all week,” she recalls.

Following a medical leave, Joglekar was able to return to MIT full time in fall 2020, and soon took another class from the Institute’s Program in Women’s and Gender Studies (WGS): WGS.250 (HIV/AIDS in American Culture). “That’s the class that made me want to be a WGS minor,” she says. “It was so nice to get a broader perspective on illness, one that was not rooted in medicine, treatment, and doctors.”

A computer science and biology major (Course 6-7), Joglekar found that the coursework for her WGS minor provided her with insight into the human factors that drive so many societal outcomes. “WGS studies helped give me a framework for understanding the world,” she says, “in the same way that my physics and math classes did.” She adds that WGS classes helped her understand myths about various minority groups, as well as the ways children are socialized to believe them.

Support for women in tech

Joglekar, who was named a Burchard Scholar in 2019 for excellence in her WGS studies, says she always knew she wanted to study the humanities, as well as the STEM fields, in college. But she didn’t only choose MIT because the Institute pairs extraordinary technical and scientific education with world-class offerings in the humanities, arts, and social sciences. She was also impressed by the gender parity she saw on a visit to campus.

While at high school in a Boston suburb, her techie classes were predominantly male; at MIT, she saw both men and women pursuing science, technology, and math. “You come here and see, oh my god, here are all these girls doing all these cool things,” she says. “I knew I would go into a technical field, and I wanted to go to a place with a lot of women in tech and a support system for women in tech.”

One of the supportive networks Joglekar found at the Institute was the lab of Tyler Jacks, the David H. Koch Professor of Biology, director of the Koch Institute for Integrative Cancer Research, and a leader in the field of cancer genetics. Working through MIT's Undergraduate Research Opportunities Program (UROP), Joglekar conducted cancer research in the Jacks lab, investigating the combination therapy potential of a small molecule inhibitor on tumor heterogeneity. “The lab was a wonderful place to learn,” she says. “They were the community I needed.”

Friendship and community

Community is of central importance to Joglekar, whose family always emphasized the importance of friendship. That’s why she has spent much of her extracurricular time at MIT supporting community-building efforts. She served on the Executive Council of the Biology Undergraduate Student Association, which runs departmental study breaks and faculty dinners. She also served on the Undergraduate Student Advisory Group for the Department of Electrical Engineering and Computer Science (EECS), which works to improve systemic issues, such as departmental communications.

The latter experience in particular gave Joglekar the chance to work directly with leaders in the EECS department. “That has been one of the highlights of my undergraduate experience,” she notes. “They’re so good at listening and taking feedback, and they have influenced how I want to be one day if ever I’m in a leadership position.”

Leadership

In fact, Joglekar served in several leadership roles during her time at MIT. In addition to her committee work, she was editor-in-chief of the MIT Undergraduate Research Journal, the Institute’s only peer-reviewed scientific journal serving the undergraduate population. And, like a good leader, she is candid about her journey. “I don’t want people to think, ‘look at this person who’s flying through life.’ Far from it. I struggled at different times for different reasons,” she says. “But I’d still do it all over again!”

Joglekar is now planning to work as a research assistant in a hospital, and expects her experience in WGS will help her understand patients better — and perhaps even address some of the social determinants of health. “WGS gives you the tools to understand so many things, including underlying biases,” she says. “I think everybody should take a WGS class for this reason. It’s relevant regardless of what you do.”

Story by MIT SHASS Communications
Editorial and design director: Emily Hiestand
Senior writer: Kathryn O'Neill

CHIME telescope detects more than 500 mysterious fast radio bursts in its first year of operation

Wed, 06/09/2021 - 12:15pm

To catch sight of a fast radio burst is to be extremely lucky in where and when you point your radio dish. Fast radio bursts, or FRBs, are oddly bright flashes of light, registering in the radio band of the electromagnetic spectrum, that blaze for a few milliseconds before vanishing without a trace.

These brief and mysterious beacons have been spotted in various and distant parts of the universe, as well as in our own galaxy. Their origins are unknown, and their appearance is unpredictable. Since the first was discovered in 2007, radio astronomers have only caught sight of around 140 bursts in their scopes.

Now, a large stationary radio telescope in British Columbia has nearly quadrupled the number of fast radio bursts discovered to date. The telescope, known as CHIME, for the Canadian Hydrogen Intensity Mapping Experiment, has detected 535 new fast radio bursts during its first year of operation, between 2018 and 2019.

Scientists with the CHIME Collaboration, including researchers at MIT, have assembled the new signals in the telescope’s first FRB catalog, which they will present this week at the American Astronomical Society Meeting.

The new catalog significantly expands the current library of known FRBs, and is already yielding clues as to their properties. For instance, the newly discovered bursts appear to fall in two distinct classes: those that repeat, and those that don’t. Scientists identified 18 FRB sources that burst repeatedly, while the rest appear to be one-offs. The repeaters also look different, with each burst lasting slightly longer and emitting more focused radio frequencies than bursts from single, nonrepeating FRBs.

These observations strongly suggest that repeaters and one-offs arise from separate mechanisms and astrophysical sources. With more observations, astronomers hope soon to pin down the extreme origins of these curiously bright signals.

“Before CHIME, there were less than 100 total discovered FRBs; now, after one year of observation, we’ve discovered hundreds more,” says CHIME member Kaitlyn Shin, a graduate student in MIT’s Department of Physics. “With all these sources, we can really start getting a picture of what FRBs look like as a whole, what astrophysics might be driving these events, and how they can be used to study the universe going forward."

Seeing flashes

CHIME comprises four massive cylindrical radio antennas, roughly the size and shape of snowboarding half-pipes, located at the Dominion Radio Astrophysical Observatory, operated by the National Research Council of Canada in British Columbia, Canada. CHIME is a stationary array, with no moving parts. The telescope receives radio signals each day from half of the sky as the Earth rotates.

While most radio astronomy is done by swiveling a large dish to focus light from different parts of the sky, CHIME stares, motionless, at the sky, and focuses incoming signals using a correlator — a powerful digital signaling processor that can work through huge amounts of data, at a rate of about 7 terabits per second, equivalent to a few percent of the world’s internet traffic.

“Digital signal processing is what makes CHIME able to reconstruct and ‘look’ in thousands of directions simultaneously,” says Kiyoshi Masui, assistant professor of physics at MIT, who will lead the group’s conference presentation. “That’s what helps us detect FRBs a thousand times more often than a traditional telescope.”

Over the first year of operation, CHIME detected 535 new fast radio bursts. When the scientists mapped their locations, they found the bursts were evenly distributed in space, seeming to arise from any and all parts of the sky. From the FRBs that CHIME was able to detect, the scientists calculated that bright fast radio bursts occur at a rate of about 800 per day across the entire sky — the most precise estimate of FRBs overall rate to date.

“That’s kind of the beautiful thing about this field — FRBs are really hard to see, but they’re not uncommon,” says Masui, who is a member of MIT’s Kavli Institute for Astrophysics and Space Research. “If your eyes could see radio flashes the way you can see camera flashes, you would see them all the time if you just looked up.”

Mapping the universe

As radio waves travel across space, any interstellar gas, or plasma, along the way can distort or disperse the wave’s properties and trajectory. The degree to which a radio wave is dispersed can give clues to how much gas it passed through, and possibly how much distance it has traveled from its source.

For each of the 535 FRBs that CHIME detected, Masui and his colleagues measured its dispersion, and found that most bursts likely originated from far-off sources within distant galaxies. The fact that the bursts were bright enough to be detected by CHIME suggests that they must have been produced by extremely energetic sources. As the telescope detects more FRBs, scientists hope to pin down exactly what kind of exotic phenomena could generate such ultrabright, ultrafast signals.

Scientists also plan to use the bursts, and their dispersion estimates, to map the distribution of gas throughout the universe.

“Each FRB gives us some information of how far they’ve propagated and how much gas they’ve propagated through,” Shin says. “With large numbers of FRBs, we can hopefully figure out how gas and matter are distributed on very large scales in the universe. So, alongside the mystery of what FRBs are themselves, there’s also the exciting potential for FRBs as powerful cosmological probes in the future.”

This research was supported by various institutions including the Canada Foundation for Innovation, the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, the Canadian Institute for Advanced Research, McGill University and the McGill Space Institute via the Trottier Family Foundation, and the University of British Columbia.

QS ranks MIT the world’s No. 1 university for 2021-22

Tue, 06/08/2021 - 4:00pm

MIT has again been named the world’s top university by the QS World University Rankings, which were announced today. This is the 10th year in a row MIT has received this distinction.

The full 2022 edition of the rankings — published by Quacquarelli Symonds, an organization specializing in education and study abroad — can be found at TopUniversities.com. The QS rankings were based on academic reputation, employer reputation, citations per faculty, student-to-faculty ratio, proportion of international faculty, and proportion of international students.

MIT was also ranked the world’s top university in 12 of the subject areas ranked by QS, as announced in March of this year.

The Institute received a No. 1 ranking in the following QS subject areas: Architecture; Chemistry; Computer Science and Information Systems; Chemical Engineering; Civil and Structural Engineering; Economics and Econometrics; Electrical and Electronic Engineering; Mechanical, Aeronautical and Manufacturing Engineering; Linguistics; Mathematics; Physics and Astronomy; and Statistics and Operational Research.

MIT also placed second in four subject areas: Accounting and Finance; Biological Sciences; Earth and Marine Sciences; and Materials Science.

“We deeply appreciate the recognition of our institution and the faculty, staff, alumni, and students that make MIT what it is — and we also tremendously admire the achievements of academic institutions around the globe,” says MIT President L. Rafael Reif. “The world benefits from a strong higher education network that delivers countless benefits for humanity, from fundamental discoveries to novel solutions to pressing challenges in climate and health, to the education of the next generation of talent. We are proud and grateful to belong to this great human community of scholars, researchers, and educators, striving together to make a better world.”

Knight Science Journalism Program at MIT partners with STAT on a new health journalism fellowship

Tue, 06/08/2021 - 2:35pm

The following is an adaptation of a joint announcement from the Knight Science Journalism Program at MIT, STAT, and the Chan-Zuckerberg Initiative.

The Knight Science Journalism Program at MIT and STAT, the award-winning Boston-based health, science, and medicine publication, have teamed up to launch the Sharon Begley-STAT Science Reporting Fellowship.

The fellowship’s goal is to better diversify the ranks of science and health journalists and to foster broader and more inclusive coverage of science. The Chan-Zuckerberg Initiative (CZI) is providing $225,000 to support the first two years of the program, which is named in honor of Sharon Begley, an acclaimed science writer for STAT who died in January from complications of lung cancer.

The nine-month fellowship is intended for early-career journalists from racial and ethnic groups underrepresented in the profession and will prepare them for a successful career in science journalism. It will combine a paid reporting apprenticeship at STAT with an educational component provided through MIT’s prestigious Knight Science Journalism (KSJ) Program. The fellowship is now accepting applications for the inaugural Begley Fellow to start in September 2021, with plans to select two additional fellows in 2022.

“KSJ is honored to be a partner in this pioneering fellowship that honors the exceptional work of Sharon Begley and offers a new opportunity to support outstanding and inclusive science and health journalism,” says Deborah Blum, director of the KSJ Program at MIT. “We appreciate the commitment of the Chan Zuckerberg Initiative to improving racial and ethnic diversity in our community, which we believe is essential to smarter and more inclusive coverage of scientific research. And we are delighted to be working with STAT, one of the best health news publications available today, in assuring the success of this project.”

Science journalism reflects the structural and systemic inequities in our society, with Black, Hispanic/Latinx, and Indigenous reporters often not getting the same opportunities as white applicants to gain relevant experience. Roughly 80 percent of science journalists are white, according to the most recent membership data from two of the leading professional organizations, with 6 percent identifying as Asian or Pacific Islander, 1-4 percent as Black, 3-4 percent as Hispanic or Latinx, and 1 percent as Native American.

“The best way to make our profession and workplace more diverse and inclusive is for news organizations to grow their own talent — and that’s exactly what Sharon aimed to do,” Gideon Gil, a STAT managing editor, says in explaining why STAT decided to create the fellowship in Begley’s name. “Sharon relished mentoring younger science journalists, and her professional progeny work at news organizations across the U.S. So we could think of no more fitting way to honor her.”

The funding from CZI will enable both KSJ and STAT to offer Begley Fellows a stipend, with a combined total of $75,000 during each term. KSJ will also provide MIT-based health insurance for each fellow. In addition, STAT plans to raise additional funding to cover fellows’ reporting expenses and the program’s administrative costs, and to keep the fellowship operating in future years.

Fellows will work at STAT’s Boston, Massachusetts, office alongside its team of experienced science and health reporters and editors. The fellows will report and write articles, with additional opportunities for building connections, mentorship, and learning across publication teams. KSJ and MIT are providing support for the university-based part of the program, which offers opportunities ranging from training seminars and other fellowship community events, university library access, and the chance to audit classes at MIT and Harvard University. The Sharon Begley-STAT Science Reporting Fellowship aims to serve as a model for expanding racial diversity in science journalism that could be replicated at other publications.

Begley, STAT’s senior science writer, was long one of the nation’s finest science journalists. She was known as a generous supporter of younger journalists and was especially eager to help other women advance in a profession that, when she began as a researcher at Newsweek in 1977, was unwelcoming. She later worked at the Wall Street Journal and Reuters, before joining STAT at its founding in 2015.

"Sharon loved working at STAT and did some of her best reporting there, and mentoring younger journalists was one of her talents and priorities,” says her husband, Ned Groth. “So, for there to be a Sharon Begley Fellow at STAT, honing their journalistic skills in association with and mentored by colleagues who were in turn mentored by Sharon, seems like a perfect tribute to her."

Her legacy includes her powerful advocacy for people of color, exemplified by a series she wrote in 2016 and 2017 about the neglect by scientists, government funders, drug makers, and hospitals of patients with sickle cell disease, who, in the United States, are predominantly Black.

“Supporting reporters from racial and ethnic groups underrepresented in journalism will bring important perspectives to the newsroom and surface new narratives and stories relevant to more communities, which will not only make biomedical reporting better and more accurate, but also help encourage greater public trust in science among historically marginalized groups,” says CZI Science Communications Manager Leah Duran. “We’re proud to support STAT and MIT to stand up this exciting program to cultivate talent and expand representation in science journalism.” In 2019, CZI supported the University of California at Santa Cruz to increase diversity, inclusion, and representation in its science journalism program.

The Sharon Begley-STAT Science Reporting Fellowship is accepting applications through June 30 at 5 p.m. For more information and application instructions, please visit KSJ’s online portal. For inquiries, technical assistance, or other questions pertaining to this application, please contact Gideon Gil or Deborah Blum.

MIT J-WAFS awards eight grants in seventh round of seed funding

Tue, 06/08/2021 - 2:00pm

The Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT has announced its seventh round of seed grant funding to the MIT community. J-WAFS is MIT’s Institute-wide initiative to promote, coordinate, and lead research related to water and food that will have a measurable and international impact as humankind adapts to a rapidly expanding population on a changing planet. The seed grant program is J-WAFS’ flagship funding initiative, aimed at catalyzing innovative research across the Institute that solves the challenges facing the world’s water and food systems.

This year, eight new projects will be funded, led by nine faculty principal investigators (PIs) across six MIT departments. The winning projects address challenges that range from climate-resilient crops, food safety technologies and innovations that can remove contaminants from water, research supporting smallholder farmers’ productivity and resilience, and more.  

Many of the projects that were selected for funding this year are focused on agriculture and food systems challenges, and these innovations could not be more timely. “Agriculture and food production are responsible for more than 30 percent of the world’s greenhouse gas emissions. Even if we could completely shut down fossil fuel emissions today, agricultural emissions would prevent us from meeting the targets of the Paris accords. Simply fixing energy systems will not be enough,” says J-WAFS Director John H. Lienhard V. “It will take researchers working in all sectors and disciplines working together to address these challenges to meet the needs of current and future populations despite the challenges posted by climate change. The innovations that are being developed at MIT, such as those that we selected for funding this year, are truly inspiring and can lead the way toward a food-secure future.” 

Water and food systems challenges are inspiring a growing number of faculty across the Institute to pursue solutions-oriented research. Over 190 MIT faculty members from across all five schools at MIT as well as the MIT Stephen A. Schwarzman College of Computing have submitted proposals to J-WAFS’ grant programs since its launch in 2015. In 2021 alone, 37 principal investigators from 17 departments across all five schools proposed to the J-WAFS seed grant program. Competing for funding were established experts in water and food-related research areas as well as professors who are only recently applying their disciplinary expertise to the world’s water and food challenges. Engineering faculty from four departments were funded, including the Departments of Civil and Environmental Engineering, Chemical Engineering, Materials Science and Engineering, and Mechanical Engineering. Additional funded principal investigators are from the Department of Biology in the School of Science, the Sloan School of Management, and the MIT Media Lab in the School of Architecture and Planning.  

The eight projects selected for J-WAFS seed grant funding and detailed below will receive $150,000, overhead-free, for two years.    

Ensuring climate resilience in agriculture and crop production

Climate change poses a grave risk to water availability and rain-fed agriculture, especially in sub-Saharan Africa. "Impact of Near-term Climate Change on Water Availability and Food Productivity in Africa," a project led by Elfatih A. B. Eltahir, the Breene M. Kerr Professor in the Department of Civil and Environmental Engineering, aims to better understand the projected near-term effects of the climate crisis on agricultural production at the southern edge of the Sahara Desert. Eltahir’s research will focus on integrating regional climate modeling with an analysis of archived observations on rainfall, temperature, and yield. His goal is to better understand how impacts of climate change on crop yields vary at the regional level. His team will work closely with other scientists and the policymakers in Africa who are in charge of planning climate change adaptation in the water and agriculture sectors to support a transition to resilient agriculture planning.

The climate crisis is projected to affect agricultural productivity worldwide. In nature, species adapt to environmental changes through the natural genetic variation that exists within a specific population. However, the time frame for this process is long and cannot meet the urgent need for food crops that are adaptable in a changing climate. With her project, "A New Approach to Enhance Genetic Diversity to Improve Crop Breeding," Mary Gehring, an associate professor in the Department of Biology, is re-imagining the future of plant breeding beyond current practices that rely on natural variation. Supported by a J-WAFS seed grant, she will develop methods that rapidly produce genetic variations in order to increase the genetic diversity of food crop species. Using pigeon pea, a legume that is widely grown as a food, they will then test these variations against environmental stresses such as heat and drought in order to identify strains that could be more adapted to climate change. 

Food loss and waste, which accounted for 32 percent of all food produced in the world in 2009, presents grand societal, economic, and environmental challenges, especially when climate change threatens current and future food supplies. In developing countries where food security is still a great concern, food loss is largely due to lack of adequate refrigeration for post-harvest food. Technologies exist for crop storage that use evaporative cooling, but they are less effective in hot and humid climates. Jeffrey C. Grossman, the Morton and Claire Goulder and Family Professor in Environmental Systems in the Department of Materials Science and Engineering, has teamed up with Evelyn N. Wang, the Gail E. Kendall Professor in the Department of Mechanical Engineering, to find a solution. With their project, "Hybrid Evaporative and Radiative Cooling as a Passive Low-cost High-performance Solution for Food Shelf-life Extension," they are developing a low-cost device using an innovative combination of two methods of cooling: evaporative and radiative technologies. Their structure will use solar-reflecting materials and highly porous insulation to double the shelf life of perishable foods in remote and rural settings, without the need for electricity.  

Addressing pathogens and pesticide contamination with novel technology

Food-borne illness represents a major source of both human morbidity and economic loss; however, current pathogen detection methods used across the United States are time- and labor-intensive. This means that food contamination is often not detected until it is already in the hands of consumers, requiring costly recalls. While rapid tests have emerged to address this challenge, they are do not have the sensitivity to detect a wide variety of contaminants. Rohit Karnik, a professor in the Department of Mechanical Engineering, has teamed up with Pratik Shah, a principal research scientist at the MIT Media Lab, to develop a food safety test that is rapid, sensitive, and easy to use. The device that they are developing with their project, "On-site Analysis of Foodborne Pathogens Using Density-Shift Immunomagnetic Separation and Culture," will use a novel technology called density-shift immunomagnetic separation (DIMS) to detect a wide variety of pathogens on-site within a matter of hours to enable on-site testing at food processing plants.  

Pesticide ingestion by humans poses another health challenge. A class of chemicals called organophosphates (OPs) — commonly used for pesticides — is particularly toxic. Though some OPs have been discontinued, many of these toxic chemicals remain widely available and continue to be used for weed control in agriculture and to reduce mosquito populations. Currently, OP can only be detected in blood or urine after a person has been exposed, and the methods for detection are costly. With her project, "Engineered Microbial Co-Cultures to Detect and Degrade Organophosphates," Ariel L. Furst, an assistant professor in the Department of Chemical Engineering, is developing a technology to more quickly and effectively detect and remove this chemical. She is engineering specific strains of bacteria to work together to both detect and degrade OPs. These bacteria will be deployed using a single electronic device, which will provide a modular, adaptable strategy to detect and degrade these harmful toxins before they are ingested.  

Aquaculture is widely recognized as an efficient system that can enable the production of healthy protein for human consumption with a minimal impact on the environment. With 85 percent of the world’s marine stocks fully exploited, it plays a pivotal role in current and future food production. However, the industry is challenged by the spread of preventable infectious diseases that cripple farmed fish populations and can cause substantial economic losses. Fish vaccines are in use for certain diseases, but effective delivery is challenging and costly, and can lead to adverse effects to the fish. Benedetto Marelli, the Paul M. Cook Career Development Associate Professor in the Department of Civil and Environmental Engineering, is developing a solution. With his project, "Precise Fish Vaccine Injection Using Silk-based Biomaterials for Sustainable Aquaculture," he is creating a microneedle for fish vaccination that is made of silk. This novel technology will enable controlled drug release in fish and will also naturally degrade in water, which will support the health of fish populations and reduce losses for aquaculture farms.

Improving the resilience of rural populations and smallholder farmers

Regions around the world that don’t have access to safe or abundant supplies of freshwater often rely on small-scale, decentralized groundwater desalination devices that use reverse osmosis. Unfortunately, these systems are extremely energy-intensive, and therefore are both expensive to operate and environmentally unsustainable. Amos G. Winter V, an associate professor in the Department of Mechanical Engineering, is working on a new design for desalination devices for settings such as these that has the potential to make reverse osmosis water treatment more affordable and better able to be powered by renewable energy. With his project, "A Sliding Vane Energy Recovery Device (ERD) for Photovoltaic-Powered Brackish Water Reverse Osmosis Desalination (PV-BWRO)," Winter and his research team will focus on affordability, energy efficiency, and ease of use in their design to ensure that the resulting technology is accessible to poor and rural communities around the world. 

Agricultural supply chains in developing countries are highly fragmented and opaque. Millions of smallholder farmers worldwide are the main producers, and often sell through a complex network of traders and intermediaries. Due to the highly fragmented nature of this system, these farmers persistently struggle with low productivity and high poverty. In an effort to find a solution, many countries have invested in mobile technologies that are intended to improve farmers’ market and information access. However, there remains a disconnect between the data that are collected and distributed via these mobile platforms and their effective use by smallholders. Yanchong Zheng, associate professor of operations management at the Sloan School of Management, aims to fill this gap with her project, "Improving Smallholder Farmers’ Welfare with AI-driven Technologies," by developing AI-driven market tools that can sift through the data to develop unbiased weather, crop planning, and pricing information. Additionally, she and her research team will develop recommendations based on these data that can more effectively inform farmers’ investments. The team will work in close collaboration with public and private sector organizations on the ground in order to ensure that their solutions are informed by the specific needs of the smallholder farmers that they seek to support. 

With the addition of these eight newly funded projects, J-WAFS will have supported 53 seed grant research projects since the program launched in 2014. The J-WAFS seed funding catalyzes new solutions-oriented research at MIT and supports MIT researchers who bring a wide variety of disciplinary tools and knowledge from working in other sectors to apply their expertise to water and food systems challenges. The results of this investment are already evident: to date, J-WAFS’ seed grant PIs have brought in nearly $15 million in follow-on funding, have published numerous papers in internationally recognized journals and publications, obtained patents, and launched spinout companies. Each project yields fresh insights and engages J-WAFS with new partners and thought leaders who drive the development of solutions at and beyond MIT.

MITEI researchers build a supply chain model to support the hydrogen economy

Tue, 06/08/2021 - 1:30pm

Over the past decades, the need for carbon-free energy has driven increasing interest in hydrogen as an environmentally clean fuel. But shifting the economy away from fossils fuels to clean-burning hydrogen will require significant adjustments in current supply chains. To facilitate this transition, an MIT-led team of researchers has developed a new hydrogen supply chain planning model.

“We propose flexible scheduling for trucks and pipelines, allowing them to serve as both storage and transmission,” says Guannan He, a postdoc at the MIT Energy Initiative (MITEI) and lead author of a recent paper published by IEEE Transactions on Sustainable Energy. “This is very important to green hydrogen produced from intermittent renewables, because this can provide extra flexibility to meet variability in supply and demand.”

Hydrogen has been widely recognized as a promising path to decarbonizing many sectors of the economy because it packs in more energy by weight than even gasoline or natural gas, yet generates zero emissions when used as an energy source. Producing hydrogen, however, can generate significant emissions. According to the U.S. Office of Energy Efficiency and Renewable Energy, 95 percent of the hydrogen produced today is generated through steam methane reforming (SMR), an energy-intensive process in which methane reacts with water to produce hydrogen and carbon monoxide. A secondary part of this process adds steam to the cooled gas to convert carbon monoxide to carbon dioxide (CO2) and produce more hydrogen.

Ultimately, hydrogen production today accounts for about 4 percent of CO2 emissions globally, says He, and that number will rise significantly if hydrogen becomes popular as a fuel for electric vehicles and such industrial processes as steel refining and ammonia production. Realizing the vision of creating an entirely decarbonized hydrogen economy therefore depends on using renewable energy to produce hydrogen, a task often accomplished through electrolysis, a process that extracts hydrogen from water electrochemically.

However, using renewable energy requires storage to move energy from times and places with peak generation to those with peak demand. And, storage is expensive.

The researchers expanded their thinking about storage to address this key concern: They used trucks in their model both as a means of fuel transmission and of storage — since hydrogen can be readily stored in idled trucks. This tactic reduces costs in the hydrogen supply chain by about 9 percent by bringing down the need for other storage solutions, says He. “We found it very important to use the trucks in this way,” says He. “It can reduce the cost of the system and encourage renewable-based hydrogen production, instead of gas-based production.”

Developing the model

Previous studies have attempted to assess the potential benefit of hydrogen storage in power systems, but they have not considered infrastructure investment needs from the perspective of a whole hydrogen supply chain, He says. And such work is critical to enabling a hydrogen economy.

For the new model, the research team — He; MITEI research scientists Emre Gençer and Dharik Mallapragada; Abhishek Bose, an MIT master’s student in technology and policy; and Clara F. Heuberger, a researcher at Shell Global Solutions International B.V. — adopted the perspective of a central planner interested in minimizing system costs and maximizing societal benefit. The researchers looked at costs associated with the four main steps in the hydrogen supply chain: production, storage, compression, and transmission. “Unless we take a holistic approach to analyzing the entire supply chain, it is hard to determine the prospects for hydrogen. This work fills that gap in the literature,” Gençer says.

To ensure their model was as comprehensive as possible, the researchers included a wide range of hydrogen-related technologies, including SMR with and without carbon capture and storage, hydrogen transport as a gas or liquid, and transmission via pipeline and trucks. “We have developed a scalable modeling and decision-making tool for a hydrogen supply chain that fully captures the flexibility of various resources as well as components,” Gençer says.

While considering all options, in the end the researchers found that pipelines were a less flexible option than trucks for transmission (although retrofitting gas pipelines could make hydrogen pipelines cost-effective for some uses), and trucking hydrogen gas was less expensive than trucking hydrogen in liquid form, since liquefaction has much higher energy consumption and capital costs than gas compression.

They then proposed a flexible scheduling and routing model for hydrogen trucks that would enable the vehicles to be used as both transmission and storage, as needed. Computationally, this was a particularly challenging step, according to He. “This is a very complex optimization model,” he says. “We propose some techniques to reduce the complexity of the model.”

The team chose to use judicious approximations for the number of trucks in the system and the needed commitment of SMR units, applying clustering and integer relaxation techniques. This enabled them to greatly improve the computational performance of their program without significantly impacting results in terms of cost and investment outcomes.

Case study of Northeast

Once the model was built, the researchers tested it by exploring the future hydrogen infrastructure needs of the U.S. Northeast under various carbon policy and hydrogen demand scenarios. Using 20 representative weeks from seven years of data, they simulated annual operations and determined the optimal mix of hydrogen infrastructure types given different carbon prices and the capital costs of electrolyzers.

“We showed that steam methane reforming of natural gas with carbon capture will constitute a significant fraction of hydrogen production and production capacity even under very high carbon price scenarios,” Gençer says.

However, He says the results also suggest there is real synergy between the use of electrolysis for hydrogen generation and the use of compressed-gas trucks for transmission and storage. This finding is important, he explains, because “once we invest in these assets, we cannot easily switch to others.”

He adds that trucks are a significantly more flexible investment than stationary infrastructure, such as pipes and transmission lines; trucks can easily be rerouted to serve new energy-generation facilities and new areas of demand, or even be left sitting to provide storage until more transmission capacity is needed. By comparison, building new electricity transmission lines or pipelines takes time — and they cannot be quickly adapted to changing needs.

“You have more renewables integrated into the system every day. People are installing rooftop solar panels, so you need more assets to transmit energy to other parts of the system,” He says, explaining that a flexible supply chain can make the most of renewable generation. “A transmission line can take 10 years to build, during which time those renewables cannot be used as well. Using smaller-scale, distributed, portable storage or mobile storage can solve this problem in a timely manner.”

Indeed, He and other colleagues recently conducted related research into the potential application of utility-scale portable energy storage in California. In a paper published in Joule in February, they showed that mobilizing energy storage can significantly increase revenues from storage in many regions and improve renewable energy integration. “It’s more flexible” than such stationary solutions as additional grid capacity, He says. “When you don’t need mobile storage anymore, you can convert it into stationary storage.”

Now that He and his colleagues have created their hydrogen supply chain planning model, the next step, according to He, is to provide planners with broad access to the tool. “We are developing open-source code so people can use it to develop optimal assets for different sectors,” He says. “We are trying to make the model better.”

This research was supported by Shell New Energies Research and Technology and the MIT Energy Initiative Low-Carbon Energy Centers for Electric Power Systems and Carbon Capture, Utilization, and Storage. The research reported in Joule was supported by the National Natural and Science Foundation of China and a grant from the U.S. Department of Energy.

Trying to put the brakes on car ownership

Tue, 06/08/2021 - 12:00am

To limit pollution and traffic congestion in Beijing, officials in 2011 imposed a citywide restriction on the number of automobiles residents can purchase annually. That policy has helped limit car sales and emissions. But the system has a loophole: Beijing residents have been going elsewhere in China to purchase cars, then bringing them home.

As a new study co-authored by MIT scholars finds, this policy “leakage” reduces the intended impact of the car-restriction system by about 35 percent. So, while Beijing adds fewer new cars per year than it once did, and its aggressive policy action has had an impact, the program also provides a case study for experts about the challenges of creative environmental and transportation policy in any setting.

One key point is the need for regional coordination in these areas, observes MIT professor Jinhua Zhao, co-author of a new paper detailing the study. Another issue is the continued need for urban design that is not automobile-centered, globally.

“If you want to design a car control policy for particular city while you don’t manage the [vehicle] flow from the region, then the policy doesn’t work,” says Zhao. “Beijing needs regional coordination among municipalities. You need to talk to your neighbor cities. It’s just like, if the city of Boston wanted to have congestion charges [for cars], all the municipalities in the Massachusetts Bay area would have to work together. Regional collaboration is one key solution.”

And while many cities in China’s have greatly added to their mass-transit capacity in recent years, Zhao notes that planners everywhere should ask: “Why do people have so much desire to own cars? The more you can provide really good and robust public transit, the less pressure there is for people to own and use cars.”

The paper, “Measuring policy leakage of Beijing’s car ownership restriction,” appears in the June issue of Transportation Research Part A: Policy and Practice. The authors are Yunhan Zheng, a graduate student in the MIT Urban Mobility Lab; Joanna Moody, a research program manager for the Mobility Systems Center of the MIT Energy Initiative; Shenhao Wang, a research scientist at the MIT Urban Mobility Lab; and Zhao, who is the associate professor of transportation and city planning in MIT’s Department of Urban Studies and Planning, and director of the MIT Mobility Initiative.

The research was supported by the Singapore-MIT Alliance for Research and Technology (SMART) Future Mobility Interdisciplinary Research Group, as well as the MIT Energy Initiative’s Mobility of the Future study.

Pollution solution

The number of private cars registered in Beijing rapidly rose from just over 900,000 in 2003, to about 3.5 million in 2010. Roughly 529,000 were added in 2009 alone.

“There’s no way you can manage this level of growth without massive congestion,” Zhao observes.

Moreover, Beijing and other Chinese cities were suffering well-publicized pollution problems. To reduce pollution, government leaders crafted several solutions, including the car-purchasing limit. From 2011 through 2013, the Beijing citywide limit was 240,000 new cars per year; now it is even lower, at 100,000 per year.

Beijing runs a lottery for applicants, to determine who can purchase vehicles.  Shanghai, another city that has crafted a similar policy, implemented an auction system in 1994, something Zhao has also studied and written about in multiple previous papers; auctioning car permits raises revenue for Shanghai and helps subsidize public transit, but in survey data, residents consider it less fair.

“They both are very aggressive policies to really push down the growth rate,” Zhao notes.

And the policies have clearly had an effect. However, despite the official limit on  new-vehicle registrations in Beijing, the actual number of new cars in the city may well be larger.

To investigate the effect of Beijing’s car ownership restriction policy on the growth of private cars in neighboring cities, the MIT researchers conducted a “difference-in-differences” analysis of car registrations in neighboring cities from 2006 to 2013, to evaluate how Beijing’s policy caused changes over time. The scholars found that in the three-year period from 2011 to 2013, after Beijing implemented its car-purchasing restrictions, vehicle sales in neighboring cities suddenly shot up by an additional 443,000 cars, above the amount the previous growth trajectory would have produced.

After accounting for various economic and demographic factors in the surrounding cities, to see if some of them had exceptional growth prospects as well, the researchers estimate that enough of those 443,000 cars would have wound up in Beijing to put that 35 percent dent in its vehicle-quota system. People were finding ways to circumvent the registration system.

“Once you draw a boundary, then you have to manage the boundary,” Zhao observes.

Connecting transportation policy

While the study is focused on Beijing, Zhao believes its findings have a variety of implications for transportation and climate policy globally — and even intersect with matters of effective governance.

“The leakage itself has different levels of consequences,” Zhao says. “One level is, the policy is not as effective. But, more importantly is that if you have a policy [avoided] by different people … then you may [damage] people’s trust of any policy.”

In this and other matters, then, it makes sense for officials and policymakers to anticipate such consumer reactions and cooperate regionally, if possible, to solve them. Or indeed, to plan regionally in the first place, from cars to transportation to climate.

“You need to talk about how to manage these things together,” Zhao says.

Moreover, Zhao notes, with the benefit of far-sighted urban planning and government provision of resources, Zhao notes, “many people wouldn’t need a car. But that requires a lot of investment, a lot of effort. To be fair to Beijing and Shanghai, they have done really well, investing in public transit. But it is still not sufficient to satisfy all the mobility demand.”

Still, if people can access jobs, schools, and commerce on foot or via public transit, that kind of provision of civic goods has profound implications for the environment — and can be a part of almost any transportation policy discussion.

“That’s where transportation policy is not just about transportation per se, it also has to connect to housing policies, to school policies, to environmental policies, and more,” Zhao says. “That leads to a broader discussion about sustainability and urban vibrancy right there.”

2021 MITx Prize winners build community on campus and across the globe

Mon, 06/07/2021 - 2:50pm

On May 14, six MIT instructors were honored with the 2021 MITx Prize for Teaching and Learning in MOOCs. The prize, established in 2016, honors excellence in creating Massive Open Online Courses (MOOCs) for MITx on edX. Anyone in the MIT community can submit nominations, including MITx MOOC creators, and awardees are selected by the MITx Faculty Advisory Committee.

The award was given to two courses this year, honoring faculty and instructors from four disciplines. Jonathan Gruber, Ford Professor of Economics, was honored for his 14.01x (AP Microeconomics) course, which uses MIT materials geared toward high school learners to help them prepare for the College Board exam. The other course recognized, 15.480x (The Science and Business of Biotechnology), was created by professors Andrew Lo of the MIT Sloan School of Management and Harvey Lodish of the Department of Biology, along with graduate students Zied Ben Chaouch of the Department of Electrical Engineering and Computer Science (EECS) and Kate Koch of the Department of Biology, as well as Shomesh Chaudhuri '14, PhD '18, an EECS graduate. 

The MITx Faculty Advisory Committee assesses prize nominees on four criteria: effective and engaging teaching methods, learner-focused innovation, residential impact and reuse, and global reach and impact. It is that last criterion that has drawn the most focus over the past year; in the wake of the Covid-19 crisis, demand for the established, high-quality resources offered by MIT Open Learning has been higher than ever.

“Now more than ever, by opening MIT teaching and learning to the world, our MITx courses are making a global impact,” says Dean for Digital Learning Krishna Rajagopal. “The courses honored with this award are exemplars of the best of MITx, and of MIT. They reach quite different audiences; high school students in one case, current and future leaders in biotechnology in the other. In both cases, they are doing so in ways that are sparking new curiosity and interest and opening new opportunities for their learners worldwide.”

Gruber’s Microeconomics course is a perfect example of a learning resource that has grown beyond its original purpose to reach a diverse international audience. Gruber first designed the course in 2017 to fill the void of preparatory materials available to U.S. students planning to take the AP Microeconomics exam; he notes that few high schools offer any kind of support or formal training for the test. The MOOC is structured around the exam curriculum, to serve either as standalone training or as a supplement to instructor-led courses. But perhaps in part because of its wide-ranging, pop-culture savvy appeal (Gruber uses LeBron James’ basketball career, Kim Kardashian’s Instagram account, and the pros and cons of attending university as just a few of his real-world economics examples) the course has found a truly global audience with learners from 180 countries.

Gruber has also used the course to develop and implement a very practical economic policy of his own. He has done away with assigning a required — and costly — textbook for his students in his residential MIT version of the course, instead assigning materials from the MOOC and other free, open source MIT learning materials as a supplement to class lectures and notes. David Autor, Ford Professor of Economics, in support of the course’s nomination, commended the “labor of love” that is Gruber’s course, and how with each new iteration of the MOOC, his colleague builds bridges for high school students, “[opening] pathways that were previously cloudy or just invisible.” Over time, says Autor, the course will “foster diversity and inclusion by seeding opportunity where it was absent.” 

The Science and Business of Biotechnology course team was no less ambitious in creating their multidisciplinary exploration of the industry, setting up the course based on the comprehensive, research-led approach they’d like to see companies adopt. Like Gruber, course leaders Andrew Lo and Harvey Lodish have personal connections to their subject: Lo was moved to make change in the sector after experiencing disillusionment with biotech during loved ones’ battles with cancer. Lodish has witnessed the enormous impact of the biotech industry on both personal and professional levels: years after he co-founded Genzyme, his daughter gave birth to a son who depends on one of the company’s medicines for treatment of a chronic health condition.

The team’s dedication and well-balanced approach to a multifaceted industry has been a smashing success. Calling Lo and Lodish “superstars” in his letter of support, Institute Professor Robert Langer lauded the course’s comprehensive approach to the subject matter, finding it essential for those who would seek to make a real impact on the biotech industry. Heidi Pickett, assistant dean for the MIT Sloan Master of Finance Program, also praised the combination of subject areas explored throughout the course, citing its ability to redress weaknesses in individual learners’ skill sets; those coming from a finance background, for example, would benefit from a deeper engagement with the science of biotech, while still gaining knowledge in their primary field. She also spoke to the course’s wide appeal: “Considering the importance of topics discussed presented in 15.480x, it is no wonder the course attracted learners from around the world bringing different backgrounds and perspectives,” she says, adding that lively exchanges between users on the course’s discussion boards greatly enhanced the learning experience.

After a year when so many learners struggled to adapt to a sudden shift to remote education, MITx Director Dana Doyle finds ample reason to celebrate the power of intentional online teaching and learning. “In a time when people everywhere have felt both increasingly isolated and increasingly connected by the experience of the pandemic, it’s so heartening to witness how these courses have brought learners together to dive into important, complex global issues.”

New drug-formulation method may lead to smaller pills

Mon, 06/07/2021 - 6:00am

About 60 percent of drugs on the market have hydrophobic molecules as their active ingredients. These drugs, which are not soluble in water, can be difficult to formulate into tablets because they need to be broken down into very small crystals in order to be absorbed by the human body.

A team of MIT chemical engineers has now devised a simpler process for incorporating hydrophobic drugs into tablets or other drug formulations such as capsules and thin films. Their technique, which involves creating an emulsion of the drug and then crystallizing it, allows for a more powerful dose to be loaded per tablet.

“This is very important because if we can achieve high drug loading, it means that we can make smaller dosages that still achieve the same therapeutic effect. This can greatly improve patient compliance because they just need to take a very small drug and it’s still very effective,” says Liang-Hsun Chen, an MIT graduate student and the lead author of the new study.

Patrick Doyle, the Robert T. Haslam Professor of Chemical Engineering, is the senior author of the paper, which appears today in Advanced Materials.

Nanoemulsions

Most medicines consist of an active ingredient that is combined with other compounds called excipients, which help to stabilize the drug and control how it is released in the body. The resulting tablets, capsules, or films are called formulations.

Currently, to create formulations of hydrophobic drugs, pharmaceutical companies use a process that requires milling the compound down to nanocrystals, which are easier for human cells to absorb. These crystals are then blended with excipients. One excipient that is often mixed with hydrophobic drugs is methylcellulose, a compound derived from cellulose. Methylcellulose dissolves easily in water, which helps drugs to be released faster in the body.

This method is widely used, but has many inefficiencies, according to the MIT team. “The milling step is very time consuming and energy intensive, and the abrasive process can cause changes in active ingredient properties, which can undermine the therapeutic effects,” Chen says.

He and Doyle set out to come up with a more efficient way to combine hydrophobic drugs with methylcellulose, by forming an emulsion. Emulsions are mixtures of oil droplets suspended in water, such as the mixture formed when an oil and vinegar salad dressing is shaken up.

When these droplets are on the scale of nanometers in diameter, this kind of mixture is called a nanoemulsion. To create their nanoemulsion, the researchers took a hydrophobic drug called fenofibrate, which is used to help lower cholesterol, and dissolved it in an oil called anisole. Then they combined this oil phase with methylcellulose dissolved in water, using ultrasonication (sound waves) to create nanoscale oil droplets. Methylcellulose helps to keep the water and oil droplets from separating again because it is amphiphilic, meaning that it can bind to both the oil droplets and the water.

Once the emulsion is formed, the researchers can transform it into a gel by dripping the liquid into a heated water bath. As each drop hits the water, it solidifies within milliseconds. The researchers can control the size of the particles by changing the size of tip that is used to drip the liquid into the water bath.

“The particle formation is nearly instantaneous, so everything that was in your liquid drop gets converted to a solid particle without any loss,” Doyle says. “After drying, we have nanocrystals of fenofibrate uniformly distributed in the methylcellulose matrix.”

Smaller pills, more drug

Once the nanocrystal-loaded particles are formed, they can be crushed into powder and then compressed into tablets, using standard drug manufacturing techniques. Alternatively, the researchers can pour their gel into molds instead of dripping it into water, allowing them to create drug tablets in any shape.

Using their nanoemulsion technique, the researchers were able to achieve drug loading of about 60 percent. In contrast, the currently available formulations of fenofibrate have a drug concentration of about 25 percent. The technique could be easily adapted to load even higher concentrations by increasing the ratio of oil to water in the emulsion, the researchers say.

“This can enable us to make more effective and smaller drugs that are easier to swallow, and that can be very beneficial for many people who have difficulty swallowing drugs,” Chen says.

This method can also be used to make thin films — a type of drug formulation that has become more widely used in recent years, and is especially beneficial for children and older people. Once a nanoemulsion is made, the researchers can dry it into a thin film that has drug nanocrystals embedded in it.

It is estimated that about 90 percent of the drugs now in development are hydrophobic, so this approach could potentially be used to develop formulations for those drugs, as well as hydrophobic drugs that are already in use, the researchers say. Many widely used drugs, including ibuprofen and other anti-inflammatory drugs such as ketoprofen and naproxen, are hydrophobic.

“The flexibility of the system is that we can choose different oils to load different drugs, and then make it into a nanoemulsion using our system. We don't need to do a lot of trial-and-error optimization because the emulsification process is the same,” Chen says.

Calvin Sun, a professor of pharmaceutics at the University of Minnesota, describes the nanoemulsion technique as an “elegant process.”

“It is impressively flexible in terms of accommodating a wide range of drug loadings and tunable drug release rate,” says Sun, who was not involved in the research. “If implemented at the commercial scale, it will have a far-reaching impact in the development of oral solid dosage forms of poorly soluble drugs.”

The research was funded by the National Science Foundation, the Singapore National Research Foundation, and the Think Global Education Trust.

Visualizing cement hydration on a molecular level

Mon, 06/07/2021 - 6:00am

The concrete world that surrounds us owes its shape and durability to chemical reactions that start when ordinary Portland cement is mixed with water. Now, MIT scientists have demonstrated a way to watch these reactions under real-world conditions, an advance that may help researchers find ways to make concrete more sustainable.

The study is a “Brothers Lumière moment for concrete science,” says co-author Franz-Josef Ulm, professor of civil and environmental engineering and faculty director of the MIT Concrete Sustainability Hub, referring to the two brothers who ushered in the era of projected films. Likewise, Ulm says, the MIT team has provided a glimpse of early-stage cement hydration that is like cinema in Technicolor compared to the black and white photos of earlier research.

Cement in concrete contributes about 8 percent of the world’s total carbon dioxide emissions, rivaling the emissions produced by most individual countries. With a better understanding of cement chemistry, scientists could potentially “alter production or change ingredients so that concrete has less of an impact on emissions, or add ingredients that are capable of actively absorbing carbon dioxide,” says Admir Masic, associate professor of civil and environmental engineering.

Next-generation technologies like 3D printing of concrete could also benefit from the study’s new imaging technique, which shows how cement hydrates and hardens in place, says Masic Lab graduate student Hyun-Chae Chad Loh, who also works as a materials scientist with the company Black Buffalo 3D Corporation.

Loh is the first author of the study published in ACS Langmuir, joining Ulm, Masic, and postdoc Hee-Jeong Rachel Kim.

Cement from the start

Loh and colleagues used a technique called Raman microspectroscopy to get a closer look at the specific and dynamic chemical reactions taking place when water and cement mix. Raman spectroscopy creates images by shining a high-intensity laser light on material and measuring the intensities and wavelengths of the light as it is scattered by the molecules that make up the material.

Different molecules and molecular bonds have their own unique scattering “fingerprints,” so the technique can be used to create chemical images of molecular structures and dynamic chemical reactions inside a material. Raman spectroscopy is often used to characterize biological and archaeological materials, as Masic has done in previous studies of nacre and other biomineralized materials and ancient Roman concretes.

Using Raman microspectroscopy, the MIT scientists observed a sample of ordinary Portland cement placed underwater without disturbing it or artificially stopping the hydration process, mimicking the real-world conditions of concrete use. In general, one of the hydration products, called portlandite, starts as a disordered phase, percolates throughout the material, and then crystallizes, the research team concluded.

Before this, “scientists could only study cement hydration with average bulk properties or with a snapshot of one point in time,” says Loh, “but this allowed us to observe all the changes almost continuously and improved the resolution of our image in space and time.”

For instance, calcium-silicate-hydrate, or C-S-H, is the main binding ingredient in cement that holds concrete together, “but it’s very difficult to detect because of its amorphous nature,” Loh explains. “Seeing its structure, distribution, and how it developed during the curing process was something that was amazing to watch.”

Building better

Ulm says the work will guide researchers as they experiment with new additives and other methods to reduce concrete’s greenhouse gas emissions: “Rather than ‘fishing in the dark,’” we are now able to rationalize through this new approach how reactions occur or do not occur, and intervene chemically.”

The team will use Raman spectroscopy as they spend the summer testing how well different cementitious materials capture carbon dioxide, Masic says. “Tracking this up to now has been almost impossible, but now we have the opportunity to follow carbonation in cementitious materials that helps us understand where the carbon dioxide goes, which phases are formed, and how to change them in order to potentially use concrete as a carbon sink.”

The imaging is also critical for Loh’s work with 3D concrete printing, which depends on extruding concrete layers in a precisely measured and coordinated process, during which the liquid slurry turns into solid concrete.

“Knowing when the concrete is going to set is the most critical question that everyone is trying to understand” in the industry, he says. “We do a lot of trial and error to optimize a design. But monitoring the underlying chemistry in space and time is critical, and this science-enabled innovation will impact the concrete printing capabilities of the construction industry.”

This work was partially supported by the scholarship program of the Kwanjeong Educational Foundation.

Tiny particles power chemical reactions

Mon, 06/07/2021 - 5:00am

MIT engineers have discovered a new way of generating electricity using tiny carbon particles that can create a current simply by interacting with liquid surrounding them.

The liquid, an organic solvent, draws electrons out of the particles, generating a current that could be used to drive chemical reactions or to power micro- or nanoscale robots, the researchers say.

“This mechanism is new, and this way of generating energy is completely new,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “This technology is intriguing because all you have to do is flow a solvent through a bed of these particles. This allows you to do electrochemistry, but with no wires.”

In a new study describing this phenomenon, the researchers showed that they could use this electric current to drive a reaction known as alcohol oxidation — an organic chemical reaction that is important in the chemical industry.

Strano is the senior author of the paper, which appears today in Nature Communications. The lead authors of the study are MIT graduate student Albert Tianxiang Liu and former MIT researcher Yuichiro Kunai. Other authors include former graduate student Anton Cottrill, postdocs Amir Kaplan and Hyunah Kim, graduate student Ge Zhang, and recent MIT graduates Rafid Mollah and Yannick Eatmon.

Unique properties

The new discovery grew out of Strano’s research on carbon nanotubes — hollow tubes made of a lattice of carbon atoms, which have unique electrical properties. In 2010, Strano demonstrated, for the first time, that carbon nanotubes can generate “thermopower waves.” When a carbon nanotube is coated with layer of fuel, moving pulses of heat, or thermopower waves, travel along the tube, creating an electrical current.

That work led Strano and his students to uncover a related feature of carbon nanotubes. They found that when part of a nanotube is coated with a Teflon-like polymer, it creates an asymmetry that makes it possible for electrons to flow from the coated to the uncoated part of the tube, generating an electrical current. Those electrons can be drawn out by submerging the particles in a solvent that is hungry for electrons.

To harness this special capability, the researchers created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side of each sheet was coated with a Teflon-like polymer, and the researchers then cut out small particles, which can be any shape or size. For this study, they made particles that were 250 microns by 250 microns.

When these particles are submerged in an organic solvent such as acetonitrile, the solvent adheres to the uncoated surface of the particles and begins pulling electrons out of them.

“The solvent takes electrons away, and the system tries to equilibrate by moving electrons,” Strano says. “There’s no sophisticated battery chemistry inside. It’s just a particle and you put it into solvent and it starts generating an electric field.”

“This research cleverly shows how to extract the ubiquitous (and often unnoticed) electric energy stored in an electronic material for on-site electrochemical synthesis,” says Jun Yao, an assistant professor of electrical and computer engineering at the University of Massachusetts at Amherst, who was not involved in the study. “The beauty is that it points to a generic methodology that can be readily expanded to the use of different materials and applications in different synthetic systems.”

Particle power

The current version of the particles can generate about 0.7 volts of electricity per particle. In this study, the researchers also showed that they can form arrays of hundreds of particles in a small test tube. This “packed bed” reactor generates enough energy to power a chemical reaction called an alcohol oxidation, in which an alcohol is converted to an aldehyde or a ketone. Usually, this reaction is not performed using electrochemistry because it would require too much external current.

“Because the packed bed reactor is compact, it has more flexibility in terms of applications than a large electrochemical reactor,” Zhang says. “The particles can be made very small, and they don’t require any external wires in order to drive the electrochemical reaction.”

In future work, Strano hopes to use this kind of energy generation to build polymers using only carbon dioxide as a starting material. In a related project, he has already created polymers that can regenerate themselves using carbon dioxide as a building material, in a process powered by solar energy. This work is inspired by carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide, using energy from the sun.

In the longer term, this approach could also be used to power micro- or nanoscale robots. Strano’s lab has already begun building robots at that scale, which could one day be used as diagnostic or environmental sensors. The idea of being able to scavenge energy from the environment to power these kinds of robots is appealing, he says.

“It means you don’t have to put the energy storage on board,” he says. “What we like about this mechanism is that you can take the energy, at least in part, from the environment.”

The research was funded by the U.S. Department of Energy and a seed grant from the MIT Energy Initiative.

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