“Can we make tissues that are made from you, for you?” asked Jennifer Lewis ScD ’91 at the 2025 Mildred S. Dresselhaus Lecture, organized by MIT.nano, on Nov. 3. “The grand challenge goal is to create these tissues for therapeutic use and, ultimately, at the whole organ scale.”

Lewis, the Hansjörg Wyss Professor of Biologically Inspired Engineering at Harvard University, is pursuing that challenge through advances in 3D printing. In her talk presented to a combined in-person and virtual audience of over 500 attendees, Lewis shared work from her lab that focuses on enhanced function in 3D printed components for use in soft electronics, robotics, and life sciences.

“How you make a material affects its structure, and it affects its properties,” said Lewis. “This perspective was a light bulb moment for me, to think about 3D printing beyond just prototyping and making shapes, but really being able to control local composition, structure, and properties across multiple scales.”

A trained materials scientist, Lewis reflected on learning to speak the language of biologists when she joined Harvard to start her own lab focused on bioprinting and biological engineering. How does one compare particles and polymers to stem cells and extracellular matrices? A key commonality, she explained, is the need for a material that can be embedded and then erased, leaving behind open channels. To meet this need, Lewis’ lab developed new 3D printing methods, sophisticated printhead designs, and viscoelastic inks — meaning the ink can go back and forth between liquid and solid form.

Displaying a video of a moving robot octopus named Octobot, Lewis showed how her group engineered two sacrificial inks that change from fluid to solid upon either warming or cooling. The concept draws inspiration from nature — plants that dynamically change in response to touch, light, heat, and hydration. For Octobot, Lewis’ team used sacrificial ink and an embedded printing process that enables free-form printing in three dimensions, rather than layer-by-layer, to create a fully soft autonomous robot. An oscillating circuit in the center guides the fuel (hydrogen peroxide), making the arms move up and down as they inflate and deflate.

From robots to whole organ engineering

“How can we leverage shape morphing in tissue engineering?” asked Lewis. “Just like our blood continuously flows through our body, we could have continuous supply of healing.”

Lewis’ lab is now working on building human tissues, primarily cardiac, kidney, and cerebral tissue, using patient-specific cells. The motivation, Lewis explained, is not only the need for human organs for people with diseases, but the fact that receiving a donated organ means taking immunosuppressants the rest of your life. If, instead, the tissue could be made from your own cells, it would be a stronger match to your own body.

“Just like we did to engineer viscoelastic matrices for embedded printing of functional and structural materials,” said Lewis, “we can take stem cells and then use our sacrificial writing method to write in perfusable vasculature.” The process uses a technique Lewis calls SWIFT — sacrificial writing into functional tissue. Sharing lab results, Lewis showed how the stem cells, differentiated into cardiac building blocks, are initially beating individually, but after being packed into a tighter space that will support SWIFT, these building blocks fuse together and become one tissue that beats synchronously. Then, her team uses a gelatin ink that solidifies or liquefies with temperature changes to print the complex design of human vessels, flushing away the ink to leave behind open lumens. The channel remains open, mimicking a blood vessel network that could have fluid actively, continuously flowing through it. “Where we’re going is to expand this not only to different tissue types, but also building in mechanisms by which we can build multi-scale vasculature,” said Lewis.

Honoring Mildred S. Dresselhaus

In closing, Lewis reflected on Dresselhaus’ positive impact on her own career. “I want to dedicate this [talk] to Millie Dresselhaus,” said Lewis. She pointed to a quote by Millie: “The best thing about having a lady professor on campus is that it tells women students that they can do it, too.” Lewis, who arrived at MIT as a materials science and engineering graduate student in the late 1980s, a time when there were very few women with engineering doctorates, noted that “just seeing someone of her stature was really an inspiration for me. I thank her very much for all that she’s done, for her amazing inspiration both as a student, as a faculty member, and even now, today.”

After the lecture, Lewis was joined by Ritu Raman, the Eugene Bell Career Development Assistant Professor of Tissue Engineering in the MIT Department of Mechanical Engineering, for a question-and-answer session. Their discussion included ideas on 3D printing hardware and software, tissue repair and regeneration, and bioprinting in space. 

“Both Mildred Dresselhaus and Jennifer Lewis have made incredible contributions to science and served as inspiring role models to many in the MIT community and beyond, including myself,” said Raman. “In my own career as a tissue engineer, the tools and techniques developed by Professor Lewis and her team have critically informed and enabled the research my lab is pursuing.”

This was the seventh Dresselhaus Lecture, named in honor of the late MIT Institute Professor Mildred Dresselhaus, known to many as the "Queen of Carbon Science.” The annual event honors a significant figure in science and engineering from anywhere in the world whose leadership and impact echo Dresselhaus’ life, accomplishments, and values. 

“Professor Lewis exemplifies, in so many ways, the spirit of Millie Dresselhaus,” said MIT.nano Director Vladimir Bulović. “Millie’s groundbreaking work, indeed, is well known; and the groundbreaking work of Professor Lewis in 3D printing and bio-inspired materials continues that legacy.”

"To really understand science policy, you have to step outside the lab and see it in action," says Jack Fletcher, an MIT PhD student in nuclear science and engineering and chair of the 15th annual Executive Visit Days (ExVD). 

Inspired by this mindset, ExVD — jointly organized by the MIT Science Policy Initiative (SPI) and the MIT Washington Office — convened a delegation of 21 MIT affiliates, including undergraduates, graduate students, and postdocs, in Washington Oct. 27-28. 

Although the government shutdown prevented the delegation’s usual visits to executive agencies, participants met with experts across the federal science and technology policy ecosystem. These discussions built connections in the nation’s capital, displayed how evidence interacts with political realities, and demonstrated how scientists, engineers, and business leaders can pursue impactful careers in public service. 

A recurring theme across meetings was that political realities and institutional constraints, not just evidence and analysis, shape policy outcomes. As Mykyta Kliapets, a PhD student at KU Leuven (Belgium) and a visiting student at the MIT Kavli Institute for Astrophysics and Space Research, reflected, “It was really helpful to hear how rarely straightforward policy environments are — sometimes, a solution that makes the most sense technically is not always politically feasible.” 

The group also heard how political forces directly impact science, from disruptions during government shutdowns to recent reductions in federal research support. Speakers underscored that effective science policy requires combined fluency in evidence, systems, and incentives.

For the first time, ExVD visited the Delegation of the European Union to the United States to meet with Francesco Maria Graziani, climate and energy counselor. He described E.U.-U.S. cooperation on energy and climate as “active and vital, but complex,” noting that the E.U. can struggle to navigate a diverse, multilevel, and variable U.S. policy landscape. “The E.U. and the U.S. share many goals, but we often operate on different timelines and with different tools,” said Graziani. He identified nuclear power, geothermal energy, and supply chain security as areas of continued E.U. and U.S. collaboration. 

Graziani also discussed ongoing collaborations like the Destination Earth project, which improves global climate models using U.S. state-level data. “As a European, hearing differences in how the U.S. navigates science policy gave me a new lens on how two advanced democracies balance innovation, regulation, and the urgency of scientific challenges,” said Sofia Karagianni, an MBA student at the MIT Sloan School of Management. 

The ExVD delegation also met with three MIT alumni at the Science and Technology Policy Institute (STPI). A federally funded research and development center, STPI provides technical and analytical support on science and technology issues to inform policy decisions by the White House Office of Science and Technology Policy (OSTP) and other federal sponsors. Recently, STPI’s research reports have focused on a number of topics including quantum computing, biotechnology, and artificial intelligence. The discussion at STPI emphasized the importance of conducting  objective analyses that have relevance for policymakers. Director Asha Balakrishnan explained how it is often useful to provide “options” in their reports, rather than “recommendations,” because policymakers benefit from understanding the advantages and disadvantages of potential policy actions.

Participants found the speakers’ reflections on career development and fellowships particularly valuable. Several speakers discussed their experiences with the AAAS Science and Technology Policy Fellowship, which places scientists and engineers in federal agencies and congressional offices for a year. 

“In speaking with former fellows, I learned just how transformative these fellowships can be for scientists seeking to apply their academic research backgrounds to a wide range of careers at the intersection of science and policy,” said Amanda Hornick, a recent doctoral graduate of the Harvard-MIT Program in Health Sciences and Technology. Eli Duggan, a graduate student in MIT's Technology and Policy Program, added that “seeing how the speakers’ work makes a real impact got me excited to apply my technical and policy background for the public good.”

The lessons from these conversations reflect the broader mission of the MIT Science Policy Initiative: to help the MIT community understand and engage with the policymaking process. SPI is a student- and postdoc-led organization dedicated to strengthening dialogue between MIT and the broader policy ecosystem. Each year, SPI organizes multiple trips to Washington, giving members the chance to meet directly with federal agencies and policymakers while exploring careers at the intersection of science, technology, and policy. These trips also spark connections and conversations that participants bring back to campus, enriching policy dialogue within the MIT community. 

SPI is grateful to the individuals and organizations who shared their time and insights at this year’s ExVD, giving participants a foundation to draw on as they explore career opportunities and the many ways technical expertise can shape public decision-making.

Students enrolled in MIT’s New Engineering Education Transformation (NEET) program recently collaborated across academic disciplines to design and construct a solar-powered charging station. Positioned in a quiet campus courtyard, the station provides the MIT community with climate-friendly power for phones, laptops, and tablets.

Its installation marked the “first time a cross-departmental team of undergraduates designed, created, and installed on campus a green technology artifact for the public good, as part of a class they took for credit,” says Amitava “Babi” Mitra, NEET founding executive director.

The project was very on-brand for the NEET program, which centers interdisciplinary, cross-departmental, and project-centric scholarship with experiential learning at its core. Launched in 2017 as an effort to reimagine undergraduate engineering education at MIT, NEET seeks to empower students to tackle complex societal challenges that straddle disciplines.

The solar-powered charging station project class is an integral part of NEET’s decarbonization-focused Climate and Sustainability Systems (CSS) “thread,” one of four pathways of study offered by the program. The class, 22.03/3.0061 (Introduction to Design Thinking and Rapid Prototyping), teaches the design and fabrication techniques used to create the station, such as laser cutting, 3D printing, computer-aided design (CAD), electronics prototyping, microcontroller programming, and composites manufacturing.

The project team included students majoring in chemical engineering, materials science and engineering, mechanical engineering, and nuclear science and engineering.

“What I really liked about this project was, at the beginning, it was really about ideation, about design, about brainstorming in ways that I haven’t seen before,” says NEET CSS student Aaron De Leon, a nuclear science and engineering major focused on clean energy development. 

During these brainstorming sessions, the team considered how their subjective design choices for the charging station would shape user experience, something De Leon, who enrolled in the class as a sophomore, says is often overlooked in engineering classes.

The team’s forest-inspired station design — complete with “tree trunks,” oyster mushroom-shaped desk space, and four solar panels curved to mimic the undulation of the forest canopy — was intended to evoke a sense of organic connectivity. The tree trunks were crafted from novel flax fiber-based composite layups the team developed through experiments designed to identify more sustainable alternatives to traditional composites.

The group also discussed how a dearth of device charging options made it difficult for students to work outside, according to NEET CSS student Celestina Pint, who enrolled in the class as a sophomore. The desk space was added to help MIT students work comfortably outdoors while also charging their devices with renewable energy.

Pint joined NEET because she wanted to “keep an open approach to climate and sustainability,” as opposed to relying on her materials science and engineering major alone, she says. “I like the interdisciplinary aspect.”

The project class presented abundant interdisciplinary learning opportunities that couldn’t be replicated in a purely theory-based curriculum, says Nathan Melenbrink, NEET lecturer, who teaches the project class and is the lead instructor for the NEET CSS thread.

For example, the team got a crash course in navigating real-world bureaucracy when they discovered that the installation of their charging station had to be approved by more than a dozen entities, including campus police, MIT’s insurance provider, and the campus facilities department.

The team also gained valuable experience with troubleshooting unanticipated design implementation challenges during the project’s fabrication phase.

“Adjustments had to be made,” Pint says. Once the station was installed, “it was interesting to see what was the same and what was different” from the team’s initial design.

This underscores a unique value of the project, according to NEET CSS student Tyler Ea, a fifth-year mechanical engineering major who joined the project team last year and is now a teaching assistant for the class.

Students “are able to take ownership of something physical, like a physical embodiment of their ideas, and something that they can point towards and say, ‘here’s something that I thought about, and this is how I went about building it, and then here’s the final result,’” he says.

While students only become eligible to join NEET in their second year, first-year students interested in the program were also able to learn from the solar-powered charging station project in the first-year discovery class SP.248 (The NEET Experience). After learning fundamental concepts in systems engineering, the class analyzed the station and suggested changes they thought would improve its design.

Melenbrink says student-built campus installations were once a hallmark of MIT’s academic culture, and he sees the NEET CSS solar-powered charging station project as an opportunity to help revive this tradition.

“What I hear from the old guard is that there was always somebody … lugging some giant, odd-looking prototype of something across campus,” Melenbrink says.

More collaborative, hands-on, student-led climate projects would also help the Institute meet its commitment to become a leading source of meaningful climate solutions, according to Elsa Olivetti, the Jerry McAfee (1940) Professor of Materials Science and Engineering and strategic advisor to the MIT Climate and Sustainability Consortium (MCSC).

“This local renewable energy project demonstrates that our campus community can learn through solution development,” she says. “Students don’t have to wait until they graduate or enter the job market to make a contribution.”

Students enrolled in this year’s Introduction to Design Thinking and Rapid Prototyping class will fabricate and install a new solar-powered charging station with a unique design. De Leon says he appreciates the latitude NEET students have to make the project their own.

“There was never the case of a professor saying, ‘We need to do it this way,’” he says. “I really liked that ability to learn as many things as you wanted to, and also have the autonomy to make your own design decisions along the way.”

“I just can’t make it tonight. You have fun without me.” Across much of the animal kingdom, when infection strikes, social contact shuts down. A new study details how the immune and central nervous systems implement this sickness behavior.

It makes perfect sense that when we’re battling an infection, we lose our desire to be around others. That protects others from getting sick and lets us get much-needed rest. What hasn’t been as clear is how this behavior change happens.

In new research published Nov. 25 in Cell, scientists at MIT’s Picower Institute for Learning and Memory and collaborators used multiple methods to demonstrate causally that when the immune system cytokine interleukin-1 beta (IL-1β) reaches the IL-1 receptor 1 (IL-1R1) on neurons in a brain region called the dorsal raphe nucleus, that activates connections with the intermediate lateral septum to shut down social behavior.

“Our findings show that social isolation following immune challenge is self-imposed and driven by an active neural process, rather than a secondary consequence of physiological symptoms of sickness, such as lethargy,” says study co-senior author Gloria Choi, associate professor in MIT’s Department of Brain and Cognitive Sciences and a member of the Picower Institute.

Jun Huh, Harvard Medical School associate professor of immunology, is the paper’s co-senior author. The lead author is Liu Yang, a research scientist in Choi’s lab.

A molecule and its receptor

Choi and Huh’s long collaboration has identified other cytokines that affect social behavior by latching on to their receptors in the brain, so in this study their team hypothesized that the same kind of dynamic might cause social withdrawal during infection. But which cytokine? And what brain circuits might be affected?

To get started, Yang and her colleagues injected 21 different cytokines into the brains of mice, one by one, to see if any triggered social withdrawal the same way that giving mice LPS (a standard way of simulating infection) did. Only IL-1β injection fully recapitulated the same social withdrawal behavior as LPS. That said, IL-1β also made the mice more sluggish.

IL-1β affects cells when it hooks up with the IL-1R1, so the team next went looking across the brain for where the receptor is expressed. They identified several regions and examined individual neurons in each. The dorsal raphe nucleus (DRN) stood out among regions, both because it is known to modulate social behavior and because it is situated next to the cerebral aqueduct, which would give it plenty of exposure to incoming cytokines in cerebrospinal fluid. The experiments identified populations of DRN neurons that express IL-1R1, including many involved in making the crucial neuromodulatory chemical serotonin.

From there, Yang and the team demonstrated that IL-1β activates those neurons, and that activating the neurons promotes social withdrawal. Moreover, they showed that inhibiting that neural activity prevented social withdrawal in mice treated with IL-1β, and they showed that shutting down the IL-1R1 in the DRN neurons also prevented social withdrawal behavior after IL-1β injection or LPS exposure. Notably, these experiments did not change the lethargy that followed IL-1β or LPS, helping to demonstrate that social withdrawal and lethargy occur through different means.

“Our findings implicate IL-1β as a primary effector driving social withdrawal during systemic immune activation,” the researchers wrote in Cell.

Tracing the circuit

With the DRN identified as the site where neurons receiving IL-1β drove social withdrawal, the next question was what circuit they effected that behavior change through. The team traced where the neurons make their circuit projections and found several regions that have a known role in social behavior. Using optogenetics, a technology that engineers cells to become controllable with flashes of light, the scientists were able to activate the DRN neurons’ connections with each downstream region. Only activating the DRN’s connections with the intermediate lateral septum caused the social withdrawal behaviors seen with IL-1β injection or LPS exposure.

In a final test, they replicated their results by exposing some mice to salmonella.

“Collectively, these results reveal a role for IL-1R1-expressing DRN neurons in mediating social withdrawal in response to IL-1β during systemic immune challenge,” the researchers wrote.

Although the study revealed the cytokine, neurons, and circuit responsible for social withdrawal in mice in detail and with demonstrations of causality, the results still inspire new questions. One is whether IL-1R1 neurons affect other sickness behaviors. Another is whether serotonin has a role in social withdrawal or other sickness behaviors.

In addition to Yang, Choi, and Huh, the paper’s other authors are Matias Andina, Mario Witkowski, Hunter King, and Ian Wickersham.

Funding for the research came from the National Institute of Mental Health, the National Research Foundation of Korea, the Denis A. and Eugene W. Chinery Fund for Neurodevelopmental Research, the Jeongho Kim Neurodevelopmental Research Fund, Perry Ha, the Simons Center for the Social Brain, the Simons Foundation Autism Research Initiative, The Picower Institute for Learning and Memory, and The Freedom Together Foundation.