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    Developing materials for stellar performance in fusion power plants

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    When Zoe Fisher was in fourth grade, her art teacher asked her to draw her vision of a dream job on paper. At the time, those goals changed like the flavor of the week in an ice cream shop — “zookeeper” featured prominently for a while — but Zoe immediately knew what she wanted to put down: a mad scientist.When Fisher stumbled upon the drawing in her parents’ Chicago home recently, it felt serendipitous because, by all measures, she has realized that childhood dream. The second-year doctoral student at MIT’s Department of Nuclear Science and Engineering (NSE) is studying materials for fusion power plants at the Plasma Science and Fusion Center (PSFC) under the advisement of Michael Short, associate professor at NSE. Dennis Whyte, Hitachi America Professor of Engineering at NSE, serves as co-advisor.On track to an MIT educationGrowing up in Chicago, Fisher had heard her parents remarking on her reasoning abilities. When she was barely a preschooler she argued that she couldn’t have been found in a purple speckled egg, as her parents claimed they had done.Fisher didn’t put together just how much she had gravitated toward science until a high school physics teacher encouraged her to apply to MIT. Passionate about both the arts and sciences, she initially worried that pursuing science would be very rigid, without room for creativity. But she knows now that exploring solutions to problems requires plenty of creative thinking.It was a visit to MIT through the Weekend Immersion in Science and Engineering (WISE) that truly opened her eyes to the potential of an MIT education. “It just seemed like the undergraduate experience here is where you can be very unapologetically yourself. There’s no fronting something you don’t want to be like. There’s so much authenticity compared to most other colleges I looked at,” Fisher says. Once admitted, Campus Preview Weekend confirmed that she belonged. “We got to be silly and weird — a version of the Mafia game was a hit — and I was like, ‘These are my people,’” Fisher laughs.Pursuing fusion at NSEBefore she officially started as a first-year in 2018, Fisher enrolled in the Freshman Pre-Orientation Program (FPOP), which starts a week before orientation starts. Each FPOP zooms into one field. “I’d applied to the nuclear one simply because it sounded cool and I didn’t know anything about it,” Fisher says. She was intrigued right away. “They really got me with that ‘star in a bottle’ line,” she laughs. (The quest for commercial fusion is to create the energy equivalent of a star in a bottle). Excited by a talk by Zachary Hartwig, Robert N. Noyce Career Development Professor at NSE, Fisher asked if she could work on fusion as an undergraduate as part of an Undergraduate Research Opportunities Program (UROP) project. She started with modeling solders for power plants and was hooked. When Fisher requested more experimental work, Hartwig put her in touch with Research Scientist David Fischer at the Plasma Science and Fusion Center (PSFC). Fisher eventually moved on to explore superconductors, which eventually morphed into research for her master’s thesis.For her doctoral research, Fisher is extending her master’s work to explore defects in ceramics, specifically in alumina (aluminum oxide). Sapphire coatings are the single-crystal equivalent of alumina, an insulator being explored for use in fusion power plants. “I eventually want to figure out what types of charge defects form in ceramics during radiation damage so we can ultimately engineer radiation-resistant sapphire,” Fisher says.When you introduce a material in a fusion power plant, stray high-energy neutrons born from the plasma can collide and fundamentally reorder the lattice, which is likely to change a range of thermal, electrical, and structural properties. “Think of a scaffolding outside a building, with each one of those joints as a different atom that holds your material in place. If you go in and you pull a joint out, there’s a chance that you pulled out a joint that wasn’t structurally sound, in which case everything would be fine. But there’s also a chance that you pull a joint out and everything alters. And [such unpredictability] is a problem,” Fisher says. “We need to be able to account for exactly how these neutrons are going to alter the lattice property,” Fisher says, and it’s one of the topics her research explores.The studies, in turn, can function as a jumping-off point for irradiating superconductors. The goals are two-fold: “I want to figure out how I can make an industry-usable ceramic you can use to insulate the inside of a fusion power plant, and then also figure out if I can take this information that I’m getting with ceramics and make it superconductor-relevant,” Fisher says. “Superconductors are the electromagnets we will use to contain the plasma inside fusion power plants. However, they prove pretty difficult to study. Since they are also ceramic, you can draw a lot of parallels between alumina and yttrium barium copper oxide (YBCO), the specific superconductor we use,” she adds. Fisher is also excited about the many experiments she performs using a particle accelerator, one of which involves measuring exactly how surface thermal properties change during radiation.Sailing new pathsIt’s not just her research that Fisher loves. As an undergrad, and during her master’s, she was on the varsity sailing team. “I worked my way into sailing with literal Olympians, I did not see that coming,” she says. Fisher participates in Chicago’s Race to Mackinac and the Melges 15 Series every chance she gets. Of all the types of boats she has sailed, she prefers dinghy sailing the most. “It’s more physical, you have to throw yourself around a lot and there’s this immediate cause and effect, which I like,” Fisher says. She also teaches sailing lessons in the summer at MIT’s Sailing Pavilion — you can find her on a small motorboat, issuing orders through a speaker.Teaching has figured prominently throughout Fisher’s time at MIT. Through MISTI, Fisher has taught high school classes in Germany and a radiation and materials class in Armenia in her senior year. She was delighted by the food and culture in Armenia and by how excited people were to learn new ideas. Her love of teaching continues, as she has reached out to high schools in the Boston area. “I like talking to groups and getting them excited about fusion, or even maybe just the concept of attending graduate school,” Fisher says, adding that teaching the ropes of an experiment one-on-one is “one of the most rewarding things.”She also learned the value of resilience and quick thinking on various other MISTI trips. Despite her love of travel, Fisher has had a few harrowing experiences with tough situations and plans falling through at the last minute. It’s when she tells herself, “Well, the only thing that you’re gonna do is you’re gonna keep doing what you wanted to do.”That eyes-on-the-prize focus has stood Fisher in good stead, and continues to serve her well in her research today. More

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      in Energy

      Puzzling out climate change

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      Shreyaa Raghavan’s journey into solving some of the world’s toughest challenges started with a simple love for puzzles. By high school, her knack for problem-solving naturally drew her to computer science. Through her participation in an entrepreneurship and leadership program, she built apps and twice made it to the semifinals of the program’s global competition.Her early successes made a computer science career seem like an obvious choice, but Raghavan says a significant competing interest left her torn.“Computer science sparks that puzzle-, problem-solving part of my brain,” says Raghavan ’24, an Accenture Fellow and a PhD candidate in MIT’s Institute for Data, Systems, and Society. “But while I always felt like building mobile apps was a fun little hobby, it didn’t feel like I was directly solving societal challenges.”Her perspective shifted when, as an MIT undergraduate, Raghavan participated in an Undergraduate Research Opportunity in the Photovoltaic Research Laboratory, now known as the Accelerated Materials Laboratory for Sustainability. There, she discovered how computational techniques like machine learning could optimize materials for solar panels — a direct application of her skills toward mitigating climate change.“This lab had a very diverse group of people, some from a computer science background, some from a chemistry background, some who were hardcore engineers. All of them were communicating effectively and working toward one unified goal — building better renewable energy systems,” Raghavan says. “It opened my eyes to the fact that I could use very technical tools that I enjoy building and find fulfillment in that by helping solve major climate challenges.”With her sights set on applying machine learning and optimization to energy and climate, Raghavan joined Cathy Wu’s lab when she started her PhD in 2023. The lab focuses on building more sustainable transportation systems, a field that resonated with Raghavan due to its universal impact and its outsized role in climate change — transportation accounts for roughly 30 percent of greenhouse gas emissions.“If we were to throw all of the intelligent systems we are exploring into the transportation networks, by how much could we reduce emissions?” she asks, summarizing a core question of her research.Wu, an associate professor in the Department of Civil and Environmental Engineering, stresses the value of Raghavan’s work.“Transportation is a critical element of both the economy and climate change, so potential changes to transportation must be carefully studied,” Wu says. “Shreyaa’s research into smart congestion management is important because it takes a data-driven approach to add rigor to the broader research supporting sustainability.”Raghavan’s contributions have been recognized with the Accenture Fellowship, a cornerstone of the MIT-Accenture Convergence Initiative for Industry and Technology. As an Accenture Fellow, she is exploring the potential impact of technologies for avoiding stop-and-go traffic and its emissions, using systems such as networked autonomous vehicles and digital speed limits that vary according to traffic conditions — solutions that could advance decarbonization in the transportation section at relatively low cost and in the near term.Raghavan says she appreciates the Accenture Fellowship not only for the support it provides, but also because it demonstrates industry involvement in sustainable transportation solutions.“It’s important for the field of transportation, and also energy and climate as a whole, to synergize with all of the different stakeholders,” she says. “I think it’s important for industry to be involved in this issue of incorporating smarter transportation systems to decarbonize transportation.”Raghavan has also received a fellowship supporting her research from the U.S. Department of Transportation.“I think it’s really exciting that there’s interest from the policy side with the Department of Transportation and from the industry side with Accenture,” she says.Raghavan believes that addressing climate change requires collaboration across disciplines. “I think with climate change, no one industry or field is going to solve it on its own. It’s really got to be each field stepping up and trying to make a difference,” she says. “I don’t think there’s any silver-bullet solution to this problem. It’s going to take many different solutions from different people, different angles, different disciplines.”With that in mind, Raghavan has been very active in the MIT Energy and Climate Club since joining about three years ago, which, she says, “was a really cool way to meet lots of people who were working toward the same goal, the same climate goals, the same passions, but from completely different angles.”This year, Raghavan is on the community and education team, which works to build the community at MIT that is working on climate and energy issues. As part of that work, Raghavan is launching a mentorship program for undergraduates, pairing them with graduate students who help the undergrads develop ideas about how they can work on climate using their unique expertise.“I didn’t foresee myself using my computer science skills in energy and climate,” Raghavan says, “so I really want to give other students a clear pathway, or a clear sense of how they can get involved.”Raghavan has embraced her area of study even in terms of where she likes to think.“I love working on trains, on buses, on airplanes,” she says. “It’s really fun to be in transit and working on transportation problems.”Anticipating a trip to New York to visit a cousin, she holds no dread for the long train trip.“I know I’m going to do some of my best work during those hours,” she says. “Four hours there. Four hours back.” More

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      in Environment

      Seeking climate connections among the oceans’ smallest organisms

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      Andrew Babbin tries to pack light for work trips. Along with the travel essentials, though, he also brings a roll each of electrical tape, duct tape, lab tape, a pack of cable ties, and some bungee cords.“It’s my MacGyver kit: You never know when you have to rig something on the fly in the field or fix a broken bag,” Babbin says.The trips Babbin takes are far out to sea, on month-long cruises, where he works to sample waters off the Pacific coast and out in the open ocean. In remote locations, repair essentials often come in handy, as when Babbin had to zip-tie a wrench to a sampling device to help it sink through an icy Antarctic lake.Babbin is an oceanographer and marine biogeochemist who studies marine microbes and the ways in which they control the cycling of nitrogen between the ocean and the atmosphere. This exchange helps maintain healthy ocean ecosystems and supports the ocean’s capacity to store carbon.By combining measurements that he takes in the ocean with experiments in his MIT lab, Babbin is working to understand the connections between microbes and ocean nitrogen, which could in turn help scientists identify ways to maintain the ocean’s health and productivity. His work has taken him to many coastal and open-ocean regions around the globe.“You really become an oceanographer and an Earth scientist to see the world,” says Babbin, who recently earned tenure as the Cecil and Ida Green Career Development Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We embrace the diversity of places and cultures on this planet. To see just a small fraction of that is special.”A powerful cycleThe ocean has been a constant presence for Babbin since childhood. His family is from Monmouth County, New Jersey, where he and his twin sister grew up playing along the Jersey shore. When they were teenagers, their parents took the kids on family cruise vacations.“I always loved being on the water,” he says. “My favorite parts of any of those cruises were the days at sea, where you were just in the middle of some ocean basin with water all around you.”In school, Babbin gravitated to the sciences, and chemistry in particular. After high school, he attended Columbia University, where a visit to the school’s Earth and environmental engineering department catalyzed a realization.“For me, it was always this excitement about the water and about chemistry, and it was this pop of, ‘Oh wow, it doesn’t have to be one or the other,’” Babbin says.He chose to major in Earth and environmental engineering, with a concentration in water resources and climate risks. After graduating in 2008, Babbin returned to his home state, where he attended Princeton University and set a course for a PhD in geosciences, with a focus on chemical oceanography and environmental microbiology. His advisor, oceanographer Bess Ward, took Babbin on as a member of her research group and invited him on several month-long cruises to various parts of the eastern tropical Pacific.“I still remember that first trip,” Babbin recalls. “It was a whirlwind. Everyone else had been to sea a gazillion times and was loading the boat and strapping things down, and I had no idea of anything. And within a few hours, I was doing an experiment as the ship rocked back and forth!”Babbin learned to deploy sampling cannisters overboard, then haul them back up and analyze the seawater inside for signs of nitrogen — an essential nutrient for all living things on Earth.As it turns out, the plants and animals that depend on nitrogen to survive are unable to take it up from the atmosphere themselves. They require a sort of go-between, in the form of microbes that “fix” nitrogen, converting it from nitrogen gas to more digestible forms. In the ocean, this nitrogen fixation is done by highly specialized microbial species, which work to make nitrogen available to phytoplankton — microscopic plant-like organisms that are the foundation of the marine food chain. Phytoplankton are also a main route by which the ocean absorbs carbon dioxide from the atmosphere.Microorganisms may also use these biologically available forms of nitrogen for energy under certain conditions, returning nitrogen to the atmosphere. These microbes can also release a byproduct of nitrous oxide, which is a potent greenhouse gas that also can catalyze ozone loss in the stratosphere.Through his graduate work, at sea and in the lab, Babbin became fascinated with the cycling of nitrogen and the role that nitrogen-fixing microbes play in supporting the ocean’s ecosystems and the climate overall. A balance of nitrogen inputs and outputs sustains phytoplankton and maintains the ocean’s ability to soak up carbon dioxide.“Some of the really pressing questions in ocean biogeochemistry pertain to this cycling of nitrogen,” Babbin says. “Understanding the ways in which this one element cycles through the ocean, and how it is central to ecosystem health and the planet’s climate, has been really powerful.”In the lab and out to seaAfter completing his PhD in 2014, Babbin arrived at MIT as a postdoc in the Department of Civil and Environmental Engineering.“My first feeling when I came here was, wow, this really is a nerd’s playground,” Babbin says. “I embraced being part of a culture where we seek to understand the world better, while also doing the things we really want to do.”In 2017, he accepted a faculty position in MIT’s Department of Earth, Atmospheric and Planetary Sciences. He set up his laboratory space, painted in his favorite brilliant orange, on the top floor of the Green Building.His group uses 3D printers to fabricate microfluidic devices in which they reproduce the conditions of the ocean environment and study microbe metabolism and its effects on marine chemistry. In the field, Babbin has led research expeditions to the Galapagos Islands and parts of the eastern Pacific, where he has collected and analyzed samples of air and water for signs of nitrogen transformations and microbial activity. His new measuring station in the Galapagos is able to infer marine emissions of nitrous oxide across a large swath of the eastern tropical Pacific Ocean. His group has also sailed to southern Cuba, where the researchers studied interactions of microbes in coral reefs.Most recently, Babbin traveled to Antarctica, where he set up camp next to frozen lakes and plumbed for samples of pristine ice water that he will analyze for genetic remnants of ancient microbes. Such preserved bacterial DNA could help scientists understand how microbes evolved and influenced the Earth’s climate over billions of years.“Microbes are the terraformers,” Babbin notes. “They have been, since life evolved more than 3 billion years ago. We have to think about how they shape the natural world and how they will respond to the Anthropocene as humans monkey with the planet ourselves.”Collective actionBabbin is now charting new research directions. In addition to his work at sea and in the lab, he is venturing into engineering, with a new project to design denitrifying capsules. While nitrogen is an essential nutrient for maintaining a marine ecosystem, too much nitrogen, such as from fertilizer that runs off into lakes and streams, can generate blooms of toxic algae. Babbin is looking to design eco-friendly capsules that scrub excess anthropogenic nitrogen from local waterways. He’s also beginning the process of designing a new sensor to measure low-oxygen concentrations in the ocean. As the planet warms, the oceans are losing oxygen, creating “dead zones” where fish cannot survive. While others including Babbin have tried to map these oxygen minimum zones, or OMZs, they have done so sporadically, by dropping sensors into the ocean over limited range, depth, and times. Babbin’s sensors could potentially provide a more complete map of OMZs, as they would be deployed on wide-ranging, deep-diving, and naturally propulsive vehicles: sharks.“We want to measure oxygen. Sharks need oxygen. And if you look at where the sharks don’t go, you might have a sense of where the oxygen is not,” says Babbin, who is working with marine biologists on ways to tag sharks with oxygen sensors. “A number of these large pelagic fish move up and down the water column frequently, so you can map the depth to which they dive to, and infer something about the behavior. And my suggestion is, you might also infer something about the ocean’s chemistry.”When he reflects on what stimulates new ideas and research directions, Babbin credits working with others, in his own group and across MIT.“My best thoughts come from this collective action,” Babbin says. “Particularly because we all have different upbringings and approach things from a different perspective.”He’s bringing this collaborative spirit to his new role, as a mission director for MIT’s Climate Project. Along with Jesse Kroll, who is a professor of civil and environmental engineering and of chemical engineering, Babbin co-leads one of the project’s six missions: Restoring the Atmosphere, Protecting the Land and Oceans. Babbin and Kroll are planning a number of workshops across campus that they hope will generate new connections, and spark new ideas, particularly around ways to evaluate the effectiveness of different climate mitigation strategies and better assess the impacts of climate on society.“One area we want to promote is thinking of climate science and climate interventions as two sides of the same coin,” Babbin says. “There’s so much action that’s trying to be catalyzed. But we want it to be the best action. Because we really have one shot at doing this. Time is of the essence.” More

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      in Energy

      How to make small modular reactors more cost-effective

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      When Youyeon Choi was in high school, she discovered she really liked “thinking in geometry.” The shapes, the dimensions … she was into all of it. Today, geometry plays a prominent role in her doctoral work under the guidance of Professor Koroush Shirvan, as she explores ways to increase the competitiveness of small modular reactors (SMRs).Central to the thesis is metallic nuclear fuel in a helical cruciform shape, which improves surface area and lowers heat flux as compared to the traditional cylindrical equivalent.A childhood in a prominent nuclear energy countryHer passion for geometry notwithstanding, Choi admits she was not “really into studying” in middle school. But that changed when she started excelling in technical subjects in her high school years. And because it was the natural sciences that first caught Choi’s eye, she assumed she would major in the subject when she went to university.This focus, too, would change. Growing up in Seoul, Choi was becoming increasingly aware of the critical role nuclear energy played in meeting her native country’s energy needs. Twenty-six reactors provide nearly a third of South Korea’s electricity, according to the World Nuclear Association. The country is also one of the world’s most prominent nuclear energy entities.In such an ecosystem, Choi understood the stakes at play, especially with electricity-guzzling technologies such as AI and electric vehicles on the rise. Her father also discussed energy-related topics with Choi when she was in high school. Being soaked in that atmosphere eventually led Choi to nuclear engineering.

      Youyeon Choi: Making small modular reactors more cost-effective

      Early work in South KoreaExcelling in high school math and science, Choi was a shoo-in for college at Seoul National University. Initially intent on studying nuclear fusion, Choi switched to fission because she saw that the path to fusion was more convoluted and was still in the early stages of exploration.Choi went on to complete her bachelor’s and master’s degrees in nuclear engineering from the university. As part of her master’s thesis, she worked on a multi-physics modeling project involving high-fidelity simulations of reactor physics and thermal hydraulics to analyze reactor cores.South Korea exports its nuclear know-how widely, so work in the field can be immensely rewarding. Indeed, after graduate school, Choi moved to Daejeon, which has the moniker “Science City.” As an intern at the Korea Atomic Energy Research Institute (KAERI), she conducted experimental studies on the passive safety systems of nuclear reactors. Choi then moved to the Korea Institute of Nuclear Nonproliferation and Control, where she worked as a researcher developing nuclear security programs for countries. Given South Korea’s dominance in the field, other countries would tap its knowledge resource to tap their own nuclear energy programs. The focus was on international training programs, an arm of which involved cybersecurity and physical protection.While the work was impactful, Choi found she missed the modeling work she did as part of her master’s thesis. Looking to return to technical research, she applied to the MIT Department of Nuclear Science and Engineering (NSE). “MIT has the best nuclear engineering program in the States, and maybe even the world,” Choi says, explaining her decision to enroll as a doctoral student.Innovative research at MITAt NSE, Choi is working to make SMRs more price competitive as compared to traditional nuclear energy power plants.Due to their smaller size, SMRs are able to serve areas where larger reactors might not work, but they’re more expensive. One way to address costs is to squeeze more electricity out of a unit of fuel — to increase the power density. Choi is doing so by replacing the traditional uranium dioxide ceramic fuel in a cylindrical shape with a metal one in a helical cruciform. Such a replacement potentially offers twin advantages: the metal fuel has high conductivity, which means the fuel will operate even more safely at lower temperatures. And the twisted shape gives more surface area and lower heat flux. The net result is more electricity for the same volume.The project receives funding from a collaboration between Lightbridge Corp., which is exploring how advanced fuel technologies can improve the performance of water-cooled SMRs, and the U.S. Department of Energy Nuclear Energy University Program.With SMR efficiencies in mind, Choi is indulging her love of multi-physics modeling, and focusing on reactor physics, thermal hydraulics, and fuel performance simulation. “The goal of this modeling and simulation is to see if we can really use this fuel in the SMR,” Choi says. “I’m really enjoying doing the simulations because the geometry is really hard to model. Because the shape is twisted, there’s no symmetry at all,” she says. Always up for a challenge, Choi learned the various aspects of physics and a variety of computational tools, including the Monte Carlo code for reactor physics.Being at MIT has a whole roster of advantages, Choi says, and she especially appreciates the respect researchers have for each other. She appreciates being able to discuss projects with Shirvan and his focus on practical applications of research. At the same time, Choi appreciates the “exotic” nature of her project. “Even assessing if this SMR fuel is at all feasible is really hard, but I think it’s all possible because it’s MIT and my PI [principal investigator] is really invested in innovation,” she says.It’s an exciting time to be in nuclear engineering, Choi says. She serves as one of the board members of the student section of the American Nuclear Society and is an NSE representative of the Graduate Student Council for the 2024-25 academic year.Choi is excited about the global momentum toward nuclear as more countries are exploring the energy source and trying to build more nuclear power plants on the path to decarbonization. “I really do believe nuclear energy is going to be a leading carbon-free energy. It’s very important for our collective futures,” Choi says. More

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      in Environment

      Designing tiny filters to solve big problems

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      For many industrial processes, the typical way to separate gases, liquids, or ions is with heat, using slight differences in boiling points to purify mixtures. These thermal processes account for roughly 10 percent of the energy use in the United States.MIT chemical engineer Zachary Smith wants to reduce costs and carbon footprints by replacing these energy-intensive processes with highly efficient filters that can separate gases, liquids, and ions at room temperature.In his lab at MIT, Smith is designing membranes with tiny pores that can filter tiny molecules based on their size. These membranes could be useful for purifying biogas, capturing carbon dioxide from power plant emissions, or generating hydrogen fuel.“We’re taking materials that have unique capabilities for separating molecules and ions with precision, and applying them to applications where the current processes are not efficient, and where there’s an enormous carbon footprint,” says Smith, an associate professor of chemical engineering.Smith and several former students have founded a company called Osmoses that is working toward developing these materials for large-scale use in gas purification. Removing the need for high temperatures in these widespread industrial processes could have a significant impact on energy consumption, potentially reducing it by as much as 90 percent.“I would love to see a world where we could eliminate thermal separations, and where heat is no longer a problem in creating the things that we need and producing the energy that we need,” Smith says.Hooked on researchAs a high school student, Smith was drawn to engineering but didn’t have many engineering role models. Both of his parents were physicians, and they always encouraged him to work hard in school.“I grew up without knowing many engineers, and certainly no chemical engineers. But I knew that I really liked seeing how the world worked. I was always fascinated by chemistry and seeing how mathematics helped to explain this area of science,” recalls Smith, who grew up near Harrisburg, Pennsylvania. “Chemical engineering seemed to have all those things built into it, but I really had no idea what it was.”At Penn State University, Smith worked with a professor named Henry “Hank” Foley on a research project designing carbon-based materials to create a “molecular sieve” for gas separation. Through a time-consuming and iterative layering process, he created a sieve that could purify oxygen and nitrogen from air.“I kept adding more and more coatings of a special material that I could subsequently carbonize, and eventually I started to get selectivity. In the end, I had made a membrane that could sieve molecules that only differed by 0.18 angstrom in size,” he says. “I got hooked on research at that point, and that’s what led me to do more things in the area of membranes.”After graduating from college in 2008, Smith pursued graduate studies in chemical engineering at the University of Texas at Austin. There, he continued developing membranes for gas separation, this time using a different class of materials — polymers. By controlling polymer structure, he was able to create films with pores that filter out specific molecules, such as carbon dioxide or other gases.“Polymers are a type of material that you can actually form into big devices that can integrate into world-class chemical plants. So, it was exciting to see that there was a scalable class of materials that could have a real impact on addressing questions related to CO2 and other energy-efficient separations,” Smith says.After finishing his PhD, he decided he wanted to learn more chemistry, which led him to a postdoctoral fellowship at the University of California at Berkeley.“I wanted to learn how to make my own molecules and materials. I wanted to run my own reactions and do it in a more systematic way,” he says.At Berkeley, he learned how make compounds called metal-organic frameworks (MOFs) — cage-like molecules that have potential applications in gas separation and many other fields. He also realized that while he enjoyed chemistry, he was definitely a chemical engineer at heart.“I learned a ton when I was there, but I also learned a lot about myself,” he says. “As much as I love chemistry, work with chemists, and advise chemists in my own group, I’m definitely a chemical engineer, really focused on the process and application.”Solving global problemsWhile interviewing for faculty jobs, Smith found himself drawn to MIT because of the mindset of the people he met.“I began to realize not only how talented the faculty and the students were, but the way they thought was very different than other places I had been,” he says. “It wasn’t just about doing something that would move their field a little bit forward. They were actually creating new fields. There was something inspirational about the type of people that ended up at MIT who wanted to solve global problems.”In his lab at MIT, Smith is now tackling some of those global problems, including water purification, critical element recovery, renewable energy, battery development, and carbon sequestration.In a close collaboration with Yan Xia, a professor at Stanford University, Smith recently developed gas separation membranes that incorporate a novel type of polymer known as “ladder polymers,” which are currently being scaled for deployment at his startup. Historically, using polymers for gas separation has been limited by a tradeoff between permeability and selectivity — that is, membranes that permit a faster flow of gases through the membrane tend to be less selective, allowing impurities to get through.Using ladder polymers, which consist of double strands connected by rung-like bonds, the researchers were able to create gas separation membranes that are both highly permeable and very selective. The boost in permeability — a 100- to 1,000-fold improvement over earlier materials — could enable membranes to replace some of the high-energy techniques now used to separate gases, Smith says.“This allows you to envision large-scale industrial problems solved with miniaturized devices,” he says. “If you can really shrink down the system, then the solutions we’re developing in the lab could easily be applied to big industries like the chemicals industry.”These developments and others have been part of a number of advancements made by collaborators, students, postdocs, and researchers who are part of Smith’s team.“I have a great research team of talented and hard-working students and postdocs, and I get to teach on topics that have been instrumental in my own professional career,” Smith says. “MIT has been a playground to explore and learn new things. I am excited for what my team will discover next, and grateful for an opportunity to help solve many important global problems.” More

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      in Environment

      Minimizing the carbon footprint of bridges and other structures

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      Awed as a young child by the majesty of the Golden Gate Bridge in San Francisco, civil engineer and MIT Morningside Academy for Design (MAD) Fellow Zane Schemmer has retained his fascination with bridges: what they look like, why they work, and how they’re designed and built.He weighed the choice between architecture and engineering when heading off to college, but, motivated by the why and how of structural engineering, selected the latter. Now he incorporates design as an iterative process in the writing of algorithms that perfectly balance the forces involved in discrete portions of a structure to create an overall design that optimizes function, minimizes carbon footprint, and still produces a manufacturable result.While this may sound like an obvious goal in structural design, it’s not. It’s new. It’s a more holistic way of looking at the design process that can optimize even down to the materials, angles, and number of elements in the nodes or joints that connect the larger components of a building, bridge, tower, etc.According to Schemmer, there hasn’t been much progress on optimizing structural design to minimize embodied carbon, and the work that exists often results in designs that are “too complex to be built in real life,” he says. The embodied carbon of a structure is the total carbon dioxide emissions of its life cycle: from the extraction or manufacture of its materials to their transport and use and through the demolition of the structure and disposal of the materials. Schemmer, who works with Josephine V. Carstensen, the Gilbert W. Winslow Career Development Associate Professor of Civil and Environmental Engineering at MIT, is focusing on the portion of that cycle that runs through construction.In September, at the IASS 2024 symposium “Redefining the Art of Structural Design in Zurich,” Schemmer and Carstensen presented their work on Discrete Topology Optimization algorithms that are able to minimize the embodied carbon in a bridge or other structure by up to 20 percent. This comes through materials selection that considers not only a material’s appearance and its ability to get the job done, but also the ease of procurement, its proximity to the building site, and the carbon embodied in its manufacture and transport.“The real novelty of our algorithm is its ability to consider multiple materials in a highly constrained solution space to produce manufacturable designs with a user-specified force flow,” Schemmer says. “Real-life problems are complex and often have many constraints associated with them. In traditional formulations, it can be difficult to have a long list of complicated constraints. Our goal is to incorporate these constraints to make it easier to take our designs out of the computer and create them in real life.”Take, for instance, a steel tower, which could be a “super lightweight, efficient design solution,” Schemmer explains. Because steel is so strong, you don’t need as much of it compared to concrete or timber to build a big building. But steel is also very carbon-intensive to produce and transport. Shipping it across the country or especially from a different continent can sharply increase its embodied carbon price tag. Schemmer’s topology optimization will replace some of the steel with timber elements or decrease the amount of steel in other elements to create a hybrid structure that will function effectively and minimize the carbon footprint. “This is why using the same steel in two different parts of the world can lead to two different optimized designs,” he explains.Schemmer, who grew up in the mountains of Utah, earned a BS and MS in civil and environmental engineering from University of California at Berkeley, where his graduate work focused on seismic design. He describes that education as providing a “very traditional, super-strong engineering background that tackled some of the toughest engineering problems,” along with knowledge of structural engineering’s traditions and current methods.But at MIT, he says, a lot of the work he sees “looks at removing the constraints of current societal conventions of doing things, and asks how could we do things if it was in a more ideal form; what are we looking at then? Which I think is really cool,” he says. “But I think sometimes too, there’s a jump between the most-perfect version of something and where we are now, that there needs to be a bridge between those two. And I feel like my education helps me see that bridge.”The bridge he’s referring to is the topology optimization algorithms that make good designs better in terms of decreased global warming potential.“That’s where the optimization algorithm comes in,” Schemmer says. “In contrast to a standard structure designed in the past, the algorithm can take the same design space and come up with a much more efficient material usage that still meets all the structural requirements, be up to code, and have everything we want from a safety standpoint.”That’s also where the MAD Design Fellowship comes in. The program provides yearlong fellowships with full financial support to graduate students from all across the Institute who network with each other, with the MAD faculty, and with outside speakers who use design in new ways in a surprising variety of fields. This helps the fellows gain a better understanding of how to use iterative design in their own work.“Usually people think of their own work like, ‘Oh, I had this background. I’ve been looking at this one way for a very long time.’ And when you look at it from an outside perspective, I think it opens your mind to be like, ‘Oh my God. I never would have thought about doing this that way. Maybe I should try that.’ And then we can move to new ideas, new inspiration for better work,” Schemmer says.He chose civil and structural engineering over architecture some seven years ago, but says that “100 years ago, I don’t think architecture and structural engineering were two separate professions. I think there was an understanding of how things looked and how things worked, and it was merged together. Maybe from an efficiency standpoint, it’s better to have things done separately. But I think there’s something to be said for having knowledge about how the whole system works, potentially more intermingling between the free-form architectural design and the mathematical design of a civil engineer. Merging it back together, I think, has a lot of benefits.”Which brings us back to the Golden Gate Bridge, Schemmer’s longtime favorite. You can still hear that excited 3-year-old in his voice when he talks about it.“It’s so iconic,” he says. “It’s connecting these two spits of land that just rise straight up out of the ocean. There’s this fog that comes in and out a lot of days. It’s a really magical place, from the size of the cable strands and everything. It’s just, ‘Wow.’ People built this over 100 years ago, before the existence of a lot of the computational tools that we have now. So, all the math, everything in the design, was all done by hand and from the mind. Nothing was computerized, which I think is crazy to think about.”As Schemmer continues work on his doctoral degree at MIT, the MAD fellowship will expose him to many more awe-inspiring ideas in other fields, leading him to incorporate some of these in some way with his engineering knowledge to design better ways of building bridges and other structures. More

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      Unlocking the hidden power of boiling — for energy, space, and beyond

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      Most people take boiling water for granted. For Associate Professor Matteo Bucci, uncovering the physics behind boiling has been a decade-long journey filled with unexpected challenges and new insights.The seemingly simple phenomenon is extremely hard to study in complex systems like nuclear reactors, and yet it sits at the core of a wide range of important industrial processes. Unlocking its secrets could thus enable advances in efficient energy production, electronics cooling, water desalination, medical diagnostics, and more.“Boiling is important for applications way beyond nuclear,” says Bucci, who earned tenure at MIT in July. “Boiling is used in 80 percent of the power plants that produce electricity. My research has implications for space propulsion, energy storage, electronics, and the increasingly important task of cooling computers.”Bucci’s lab has developed new experimental techniques to shed light on a wide range of boiling and heat transfer phenomena that have limited energy projects for decades. Chief among those is a problem caused by bubbles forming so quickly they create a band of vapor across a surface that prevents further heat transfer. In 2023, Bucci and collaborators developed a unifying principle governing the problem, known as the boiling crisis, which could enable more efficient nuclear reactors and prevent catastrophic failures.For Bucci, each bout of progress brings new possibilities — and new questions to answer.“What’s the best paper?” Bucci asks. “The best paper is the next one. I think Alfred Hitchcock used to say it doesn’t matter how good your last movie was. If your next one is poor, people won’t remember it. I always tell my students that our next paper should always be better than the last. It’s a continuous journey of improvement.”From engineering to bubblesThe Italian village where Bucci grew up had a population of about 1,000 during his childhood. He gained mechanical skills by working in his father’s machine shop and by taking apart and reassembling appliances like washing machines and air conditioners to see what was inside. He also gained a passion for cycling, competing in the sport until he attended the University of Pisa for undergraduate and graduate studies.In college, Bucci was fascinated with matter and the origins of life, but he also liked building things, so when it came time to pick between physics and engineering, he decided nuclear engineering was a good middle ground.“I have a passion for construction and for understanding how things are made,” Bucci says. “Nuclear engineering was a very unlikely but obvious choice. It was unlikely because in Italy, nuclear was already out of the energy landscape, so there were very few of us. At the same time, there were a combination of intellectual and practical challenges, which is what I like.”For his PhD, Bucci went to France, where he met his wife, and went on to work at a French national lab. One day his department head asked him to work on a problem in nuclear reactor safety known as transient boiling. To solve it, he wanted to use a method for making measurements pioneered by MIT Professor Jacopo Buongiorno, so he received grant money to become a visiting scientist at MIT in 2013. He’s been studying boiling at MIT ever since.Today Bucci’s lab is developing new diagnostic techniques to study boiling and heat transfer along with new materials and coatings that could make heat transfer more efficient. The work has given researchers an unprecedented view into the conditions inside a nuclear reactor.“The diagnostics we’ve developed can collect the equivalent of 20 years of experimental work in a one-day experiment,” Bucci says.That data, in turn, led Bucci to a remarkably simple model describing the boiling crisis.“The effectiveness of the boiling process on the surface of nuclear reactor cladding determines the efficiency and the safety of the reactor,” Bucci explains. “It’s like a car that you want to accelerate, but there is an upper limit. For a nuclear reactor, that upper limit is dictated by boiling heat transfer, so we are interested in understanding what that upper limit is and how we can overcome it to enhance the reactor performance.”Another particularly impactful area of research for Bucci is two-phase immersion cooling, a process wherein hot server parts bring liquid to boil, then the resulting vapor condenses on a heat exchanger above to create a constant, passive cycle of cooling.“It keeps chips cold with minimal waste of energy, significantly reducing the electricity consumption and carbon dioxide emissions of data centers,” Bucci explains. “Data centers emit as much CO2 as the entire aviation industry. By 2040, they will account for over 10 percent of emissions.”Supporting studentsBucci says working with students is the most rewarding part of his job. “They have such great passion and competence. It’s motivating to work with people who have the same passion as you.”“My students have no fear to explore new ideas,” Bucci adds. “They almost never stop in front of an obstacle — sometimes to the point where you have to slow them down and put them back on track.”In running the Red Lab in the Department of Nuclear Science and Engineering, Bucci tries to give students independence as well as support.“We’re not educating students, we’re educating future researchers,” Bucci says. “I think the most important part of our work is to not only provide the tools, but also to give the confidence and the self-starting attitude to fix problems. That can be business problems, problems with experiments, problems with your lab mates.”Some of the more unique experiments Bucci’s students do require them to gather measurements while free falling in an airplane to achieve zero gravity.“Space research is the big fantasy of all the kids,” says Bucci, who joins students in the experiments about twice a year. “It’s very fun and inspiring research for students. Zero g gives you a new perspective on life.”Applying AIBucci is also excited about incorporating artificial intelligence into his field. In 2023, he was a co-recipient of a multi-university research initiative (MURI) project in thermal science dedicated solely to machine learning. In a nod to the promise AI holds in his field, Bucci also recently founded a journal called AI Thermal Fluids to feature AI-driven research advances.“Our community doesn’t have a home for people that want to develop machine-learning techniques,” Bucci says. “We wanted to create an avenue for people in computer science and thermal science to work together to make progress. I think we really need to bring computer scientists into our community to speed this process up.”Bucci also believes AI can be used to process huge reams of data gathered using the new experimental techniques he’s developed as well as to model phenomena researchers can’t yet study.“It’s possible that AI will give us the opportunity to understand things that cannot be observed, or at least guide us in the dark as we try to find the root causes of many problems,” Bucci says. More

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      Transforming fusion from a scientific curiosity into a powerful clean energy source

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      If you’re looking for hard problems, building a nuclear fusion power plant is a pretty good place to start. Fusion — the process that powers the sun — has proven to be a difficult thing to recreate here on Earth despite decades of research.“There’s something very attractive to me about the magnitude of the fusion challenge,” Hartwig says. “It’s probably true of a lot of people at MIT. I’m driven to work on very hard problems. There’s something intrinsically satisfying about that battle. It’s part of the reason I’ve stayed in this field. We have to cross multiple frontiers of physics and engineering if we’re going to get fusion to work.”The problem got harder when, in Hartwig’s last year in graduate school, the Department of Energy announced plans to terminate funding for the Alcator C-Mod tokamak, a major fusion experiment in MIT’s Plasma Science and Fusion Center that Hartwig needed to do to graduate. Hartwig was able to finish his PhD, and the scare didn’t dissuade him from the field. In fact, he took an associate professor position at MIT in 2017 to keep working on fusion.“It was a pretty bleak time to take a faculty position in fusion energy, but I am a person who loves to find a vacuum,” says Hartwig, who is a newly tenured associate professor at MIT. “I adore a vacuum because there’s enormous opportunity in chaos.”Hartwig did have one very good reason for hope. In 2012, he had taken a class taught by Professor Dennis Whyte that challenged students to design and assess the economics of a nuclear fusion power plant that incorporated a new kind of high-temperature superconducting magnet. Hartwig says the magnets enable fusion reactors to be much smaller, cheaper, and faster.Whyte, Hartwig, and a few other members of the class started working nights and weekends to prove the reactors were feasible. In 2017, the group founded Commonwealth Fusion Systems (CFS) to build the world’s first commercial-scale fusion power plants.Over the next four years, Hartwig led a research project at MIT with CFS that further developed the magnet technology and scaled it to create a 20-Tesla superconducting magnet — a suitable size for a nuclear fusion power plant.The magnet and subsequent tests of its performance represented a turning point for the industry. Commonwealth Fusion Systems has since attracted more than $2 billion in investments to build its first reactors, while the fusion industry overall has exceeded $8 billion in private investment.The old joke in fusion is that the technology is always 30 years away. But fewer people are laughing these days.“The perspective in 2024 looks quite a bit different than it did in 2016, and a huge part of that is tied to the institutional capability of a place like MIT and the willingness of people here to accomplish big things,” Hartwig says.A path to the starsAs a child growing up in St. Louis, Hartwig was interested in sports and playing outside with friends but had little interest in physics. When he went to Boston University as an undergraduate, he studied biomedical engineering simply because his older brother had done it, so he thought he could get a job. But as he was introduced to tools for structural experiments and analysis, he found himself more interested in how the tools worked than what they could do.“That led me to physics, and physics ended up leading me to nuclear science, where I’m basically still doing applied physics,” Hartwig explains.Joining the field late in his undergraduate studies, Hartwig worked hard to get his physics degree on time. After graduation, he was burnt out, so he took two years off and raced his bicycle competitively while working in a bike shop.“There’s so much pressure on people in science and engineering to go straight through,” Hartwig says. “People say if you take time off, you won’t be able to get into graduate school, you won’t be able to get recommendation letters. I always tell my students, ‘It depends on the person.’ Everybody’s different, but it was a great period for me, and it really set me up to enter graduate school with a more mature mindset and to be more focused.”Hartwig returned to academia as a PhD student in MIT’s Department of Nuclear Science and Engineering in 2007. When his thesis advisor, Dennis Whyte, announced a course focused on designing nuclear fusion power plants, it caught Hartwig’s eye. The final projects showed a surprisingly promising path forward for a fusion field that had been stagnant for decades. The rest was history.“We started CFS with the idea that it would partner deeply with MIT and MIT’s Plasma Science and Fusion Center to leverage the infrastructure, expertise, people, and capabilities that we have MIT,” Hartwig says. “We had to start the company with the idea that it would be deeply partnered with MIT in an innovative way that hadn’t really been done before.”Guided by impactHartwig says the Department of Nuclear Science and Engineering, and the Plasma Science and Fusion Center in particular, have seen a huge influx in graduate student applications in recent years.“There’s so much demand, because people are excited again about the possibilities,” Hartwig says. “Instead of having fusion and a machine built in one or two generations, we’ll hopefully be learning how these things work in under a decade.”Hartwig’s research group is still testing CFS’ new magnets, but it is also partnering with other fusion companies in an effort to advance the field more broadly.Overall, when Hartwig looks back at his career, the thing he is most proud of is switching specialties every six years or so, from building equipment for his PhD to conducting fundamental experiments to designing reactors to building magnets.“It’s not that traditional in academia,” Hartwig says. “Where I’ve found success is coming into something new, bringing a naivety but also realism to a new field, and offering a different toolkit, a different approach, or a different idea about what can be done.”Now Hartwig is onto his next act, developing new ways to study materials for use in fusion and fission reactors.“I’m already interested in moving on to the next thing; the next field where I’m not a trained expert,” Hartwig says. “It’s about identifying where there’s stagnation in fusion and in technology, where innovation is not happening where we desperately need it, and bringing new ideas to that.” More

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      Catherine Wolfram: High-energy scholar

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      In the mid 2000s, Catherine Wolfram PhD ’96 reached what she calls “an inflection point” in her career. After about a decade of studying U.S. electricity markets, she had come to recognize that “you couldn’t study the energy industries without thinking about climate mitigation,” as she puts it.At the same time, Wolfram understood that the trajectory of energy use in the developing world was a massively important part of the climate picture. To get a comprehensive grasp on global dynamics, she says, “I realized I needed to start thinking about the rest of the world.”An accomplished scholar and policy expert, Wolfram has been on the faculty at Harvard University, the University of California at Berkeley — and now MIT, where she is the William Barton Rogers Professor in Energy. She has also served as deputy assistant secretary for climate and energy economics at the U.S. Treasury.Yet even leading experts want to keep learning. So, when she hit that inflection point, Wolfram started carving out a new phase of her research career.“One of the things I love about being an academic is, I could just decide to do that,” Wolfram says. “I didn’t need to check with a boss. I could just pivot my career to being more focused to thinking about energy in the developing world.”Over the last decade, Wolfram has published a wide array of original studies about energy consumption in the developing world. From Kenya to Mexico to South Asia, she has shed light on the dynamics of economics growth and energy consumption — while spending some of that time serving the government too. Last year, Wolfram joined the faculty of the MIT Sloan School of Management, where her work bolsters the Institute’s growing effort to combat climate change.Studying at MITWolfram largely grew up in Minnesota, where her father was a legal scholar, although he moved to Cornell University around the time she started high school. As an undergraduate, she majored in economics at Harvard University, and after graduation she worked first for a consultant, then for the Massachusetts Department of Public Utilities, the agency regulating energy rates. In the latter job, Wolfram kept noticing that people were often citing the research of an MIT scholar named Paul Joskow (who is now the Elizabeth and James Killian Professor of Economics Emeritus in MIT’s Department of Economics) and Richard Schmalensee (a former dean of the MIT Sloan School of Management and now the Howard W. Johnson Professor of Management Emeritus). Seeing how consequential economics research could be for policymaking, Wolfram decided to get a PhD in the field and was accepted into MIT’s doctoral program.“I went into graduate school with an unusually specific view of what I wanted to do,” Wolfram says. “I wanted to work with Paul Joskow and Dick Schmalensee on electricity markets, and that’s how I wound up here.”At MIT, Wolfram also ended up working extensively with Nancy Rose, the Charles P. Kindleberger Professor of Applied Economics and a former head of the Department of Economics, who helped oversee Wolfram’s thesis; Rose has extensively studied market regulation as well.Wolfram’s dissertation research largely focused on price-setting behavior in the U.K.’s newly deregulated electricity markets, which, it turned out, applied handily to the U.S., where a similar process was taking place. “I was fortunate because this was around the time California was thinking about restructuring, as it was known,” Wolfram says. She spent four years on the faculty at Harvard, then moved to UC Berkeley. Wolfram’s studies have shown that deregulation has had some medium-term benefits, for instance in making power plants operate more efficiently.Turning on the ACBy around 2010, though, Wolfram began shifting her scholarly focus in earnest, conducting innovative studies about energy in the developing world. One strand of her research has centered on Kenya, to better understand how more energy access for people without electricity might fit into growth in the developing world.In this case, Wolfram’s perhaps surprising conclusion is that electrification itself is not a magic ticket to prosperity; people without electricity are more eager to adopt it when they have a practical economic need for it. Meanwhile, they have other essential needs that are not necessarily being addressed.“The 800 million people in the world who don’t have electricity also don’t have access to good health care or running water,” Wolfram says. “Giving them better housing infrastructure is important, and harder to tackle. It’s not clear that bringing people electricity alone is the single most useful thing from a development perspective. Although electricity is a super-important component of modern living.”Wolfram has even delved into topics such as air conditioner use in the developing world — an important driver of energy use. As her research shows, many countries, with a combined population far bigger than the U.S., are among the fastest-growing adopters of air conditioners and have an even greater need for them, based on their climates. Adoption of air conditioning within those countries also is characterized by marked economic inequality.From early 2021 until late 2022, Wolfram also served in the administration of President Joe Biden, where her work also centered on global energy issues. Among other things, Wolfram was part of the team working out a price-cap policy for Russian oil exports, a concept that she thinks could be applied to many other products globally. Although, she notes, working with countries heavily dependent on exporting energy materials will always require careful engagement.“We need to be mindful of that dependence and importance as we go through this massive effort to decarbonize the energy sector and shift it to a whole new paradigm,” Wolfram says.At MIT againStill, she notes, the world does need a whole new energy paradigm, and fast. Her arrival at MIT overlaps with the emergence of a new Institute-wide effort, the Climate Project at MIT, that aims to accelerate and scale climate solutions and good climate policy, including through the new Climate Policy Center at MIT Sloan. That kind of effort, Wolfram says, matters to her.“It’s part of why I’ve come to MIT,” Wolfram says. “Technology will be one part of the climate solution, but I do think an innovative mindset, how can we think about doing things better, can be productively applied to climate policy.” On being at MIT, she adds: “It’s great, it’s awesome. One of the things that pleasantly surprised me is how tight-knit and friendly the MIT faculty all are, and how many interactions I’ve had with people from other departments.”Wolfram has also been enjoying her teaching at MIT, and will be offering a large class in spring 2025, 15.016 (Climate and Energy in the Global Economy), that she debuted this past academic year.“It’s super fun to have students from around the world, who have personal stories and knowledge of energy systems in their countries and can contribute to our discussions,” she says.When it comes to tackling climate change, many things seem daunting. But there is still a world of knowledge to be acquired while we try to keep the planet from overheating, and Wolfram has a can-do attitude about learning more and applying those lessons.“We’ve made a lot of progress,” Wolfram says. “But we still have a lot more to do.” More