Author: MIT News

Susan Solomon, scholar of atmospheric chemistry and environmental policy, delivers Killian Lecture

by Alison Gold | School of Science |

Susan Solomon, an atmospheric chemist whose work explaining the Antarctic ozone hole informed international policy, has received the 2020-2021 James R. Killian, Jr. Faculty Achievement Award. The highest such honor at the Institute, the award was established in 1971 to honor Killian, who served as MIT’s 10th president from 1948 to 1959, and chair of the MIT Corporation from 1959 to 1971.

As this year’s recipient, Solomon on April 14 delivered a one-hour lecture in which she touched on her path to MIT, her time in Antarctica, her work on ozone depletion, and her insights on the state of climate policy.

Solomon is the Lee and Geraldine Martin Professor of Environmental Studies in the Department of Earth, Atmospheric, and Planetary Sciences. She arrived at MIT in 2012, following 30 years at the National Oceanic and Atmospheric Administration. Though both an Antarctic glacier and a snow saddle bear her name, at the lecture, Solomon described the Killian award as “the most wonderful honor that anyone could get.”

Solomon “is the embodiment of MIT’s motto ‘mens et manus’ or ‘mind and hand,’ and of our mission to generate, disseminate, and preserve knowledge, and to work with others to bring this knowledge to bear on the world’s great challenges,” said Rick Danheiser, the Arthur C. Cope Professor of Chemistry and current chair of the faculty, who introduced Solomon.

Solomon had an affinity for science and the beauty of the natural world long before she was exploring the Antarctic alongside penguins. Growing up, Solomon would travel every year with her family from their home in Chicago to Indiana Dunes National Park. Around age 10, she was inspired by the wonderful adventures of French explorer and scientist Jacques Cousteau on TV. Solomon decided to pursue a career in science, and soon discovered an interest in chemistry.

“At some point, I found out that there was really such a thing as chemistry in a planet’s atmosphere — not in a test tube,” she said. “And I was absolutely fascinated by that.”

In 1974, scientists at the University of California at Irvine identified that chlorofluorocarbons (CFCs) — compounds which were becoming increasingly popular for use in canned hairsprays, deodorants, and cleaning supplies, as well as refrigeration and cooling systems — had devastating effects on Earth’s ozone. Even worse, once the compounds were released, they couldn’t be destroyed. Rather, they were destined to remain in the atmosphere for 40 to 150 years.

Ozone is a gas made of three oxygen atoms, and much of it can be found in the stratosphere. The stratosphere is the second layer of Earth’s atmosphere, located between 9 and 50 miles above the Earth. CFCs were depleting the layer of ozone located there, which helps to filter out ultraviolet radiation that can be toxic to living beings. Without ozone, life wouldn’t exist on Earth. And with reduced levels of ozone, there could be increases in skin cancer and cataracts.

In 1985, scientists discovered a large, shocking “hole” in the Antarctic ozone layer.

“I was very, very fortunate to be working with Rolando Garcia at [National Center for Atmospheric Research] at the time that the ozone hole was discovered,” Solomon said. “We began to think about what might be causing it, and what we came up with, basically, was this chemical process which turned out to be the right answer.”

Between 1985 and 1987, scientists from around the world independently studied ozone levels to verify the scope of the problem. In 1986, Solomon first set foot in Antarctica as part of the National Ozone Expedition.

What followed these scientific investigations was a triumph of international climate policy: the Montreal Protocol, a 1987 document signed by all members of the United Nations. The document was designed to limit CFC emissions and to restore the ozone layer. “It’s the only treaty that has that level of participation,” Solomon said.

Solomon said that swift action on the issue came down to the three “p’s”: The ozone issue was personal, perceptible, and practical. Risks posed by CFCs were personal because they could spike cancer and cataract risk; perceptible because many nations were monitoring ozone levels and noticed the change; and practical because replacements were discovered.

“I think when we think about almost any environmental problem, we can apply that rubric, and it will help us to understand what’s going on,” Solomon said, identifying smog and lead as examples. She is currently working on a book about the three p’s.

Solomon went on to receive the United States National Medal of Science in 1999, the nation’s highest scientific honor. In 2007, she and her colleagues on the Intergovernmental Panel on Climate Change shared the Nobel Peace Prize with former Vice President Al Gore. This January, she was awarded the National Academy of Sciences Award for Chemistry in service to society.

AT MIT, Solomon is not only faculty in two departments, but also the founding director of the Environmental Solutions Initiative, an Institute-wide coalition of experts working to address the serious challenges posed by climate change.

“It’s amazing at MIT how everyone you meet is very, very good at what they do,” Solomon said. “It’s an astonishing place. I want to thank the EAPS and chemistry faculties for making me feel so welcome. I can’t imagine a better place to live, do research, and teach.”

Ozone-depleting chemicals may spend less time in the atmosphere than previously thought

by Jennifer Chu | MIT News Office |

MIT scientists have found that ozone-depleting chlorofluorocarbons, or CFCs, stay in the atmosphere for a shorter amount of time than previously estimated. Their study suggests that CFCs, which were globally phased out in 2010, should be circulating at much lower concentrations than what has recently been measured.

The new results, published today in Nature Communications, imply that new, illegal production of CFCs has likely occurred in recent years. Specifically, the analysis points to new emissions of CFC-11, CFC-12, and CFC-113. These emissions would be in violation of the Montreal Protocol, the international treaty designed to phase out the production and consumption of CFCs and other ozone-damaging chemicals.

The current study’s estimates of new global CFC-11 emissions is higher than what previous studies report. This is also the first study to quantify new global emissions of CFC-12 and CFC-113.

“We find total emissions coming from new production is on the order of 20 gigagrams a year for each of these molecules,” says lead author Megan Lickley, a postdoc in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “This is higher than what previous scientists suggested for CFC-11, and also identifies likely new emissions of CFC-12 and 113, which previously had been overlooked. Because CFCs are such potent greenhouse gases and destroy the ozone layer, this work has important implications for the health of our planet.”

The study’s co-authors include Sarah Fletcher at Stanford University, Matt Rigby at the University of Bristol, and Susan Solomon, the Lee and Geraldine Martin Professor of Environmental Studies in MIT’s Department of Earth, Atmospheric and Planetary Sciences.

Banking on lifetimes

Prior to their global phaseout, CFCs were widely used in the manufacturing of refrigerants, aerosol sprays, chemical solvents, and building insulation. When they are emitted into the atmosphere, the chemicals can loft to the stratosphere, where they interact with ultraviolet light to release chlorine atoms, the potent agents that erode the Earth’s protective ozone.

Today, CFCs are mostly emitted by “banks” — old refrigerators, air conditioners, and insulation that were manufactured before the chemical ban and have since been slowly leaking CFCs into the atmosphere. In a study published last year, Lickley and her colleagues calculated the amount of CFCs still remaining in banks today.

They did so by developing a model that analyzes industry production of CFCs over time, and how quickly various equipment types release CFCs over time, to estimate the amount of CFCs stored in banks. They then incorporated current recommended values for the chemicals’ lifetimes to calculate the concentrations of bank-derived CFCs that should be in the atmosphere over time. Subtracting these bank emissions from total global emissions should yield any unexpected, illegal CFC production. In their new paper, the researchers looked to improve the estimates of CFC lifetimes.

“Current best estimates of atmospheric lifetimes have large uncertainties,” Lickley says. “This implies that global emissions also have large uncertainties. To refine our estimates of global emissions, we need a better estimate of atmospheric lifetimes.”

Updated spike

Rather than consider the lifetimes and emissions of each gas separately, as most models do, the team looked at CFC-11, 12, and 113 together, in order to account for similar atmospheric processes that influence their lifetimes (such as winds). These processes have been modeled by seven different chemistry-climate models, each of which provides an estimate of the gas’ atmospheric lifetime over time.

“We begin by assuming the models are all equally likely,” Lickley says. “Then we update how likely each of these models are, based on how well they match observations of CFC concentrations taken from 1979 to 2016.”

After including these chemistry-climate modeled lifetimes into a Bayesian simulation model of production and emissions, the team was able to reduce the uncertainty in their lifetime estimates. They calculated the lifetimes for CFC-11, 12, and 113 to be 49 years, 85 years, and 80 years, respectively, compared with current best values of 52, 100, and 85 years.

“Because our estimates are shorter than current best-recommended values, this implies emissions are likely higher than what best estimates have been,” Lickley says.

To test this idea, the team looked at how the shorter CFC lifetimes would affect estimates of unexpected emissions, particularly between 2014 and 2016. During this period, researchers previously identified a spike in CFC-11 emissions and subsequently traced half of these emissions to eastern China. Scientists have since observed an emissions decrease from this region, indicating that any illegal production there has stopped, though the source of the remaining unexpected emissions is still unknown.

When Lickley and her colleagues updated their estimates of CFC bank emissions and compared them with total global emissions for this three-year period, they found evidence for new, unexpected emissions on the order of 20 gigagrams, or 20 billion grams, for each chemical.

The results suggest that during this period, there was new, illegal production of CFC-11 that was higher than previous estimates, in addition to new production of CFC-12 and 113, which had not been seen before. Together, Lickley estimates that these new CFC emissions are equivalent to the total yearly greenhouse gas emissions emitted by the United Kingdom.

It’s not entirely surprising to find unexpected emissions of CFC-12, as the chemical is often co-produced in manufacturing processes that emit CFC-11. For CFC-113, the chemical’s use is permitted under the Montreal Protocol as a feedstock to make other chemicals. But the team calculates that unexpected emissions of CFC-113 are about 10 times higher than what the treaty currently allows.

“With all three gases, emissions are much lower than what they were at their peak,” Lickley says. “But they’re very potent greenhouse gases. Pound for pound, they’re five to 10,000 times more of a global warming chemical than carbon dioxide. And we’re currently facing a climate crisis where every source of emission that we can reduce will have a lasting impact on the climate system. By targeting these CFCs, we would essentially be reducing some contribution to climate change.”

This research was supported in part by VoLo Foundation.

Paula Hammond and Arup Chakraborty named Institute Professors

by Anne Trafton | MIT News Office |

Two distinguished MIT chemical engineers, Arup K. Chakraborty and Paula Hammond, have been named Institute Professors, the highest honor bestowed upon MIT faculty members.

Hammond, who chairs MIT’s Department of Chemical Engineering, is renowned for her work in developing novel polymers and nanomaterials, while Chakraborty, the founding director of MIT’s Institute for Medical Engineering and Science (IMES), is a pioneer in applying computational techniques to challenges in the field of immunology, including vaccine development.

“At MIT, the distinction of Institute Professor designates the best of the best — and that is exactly how I would describe Paula Hammond and Arup Chakraborty,” says MIT President L. Rafael Reif.

“Paula’s boldness and creativity as an engineer, her excellence as an educator, and her leadership on issues of equity and inclusion have long made her an MIT star,” Reif says. “Arup is perhaps best known as the visionary founding director of IMES and, of course, for his seminal contributions toward the development of a vaccine for HIV. I have always admired his extraordinary ability to explain complex issues — across a range of disciplines — with precision and clarity. Paula and Arup are great ambassadors for the Institute and our community. More than that, they are among MIT’s finest citizens.”

The appointments were announced today in an email to the faculty from Provost Martin Schmidt and chair of the faculty Rick Danheiser. With the addition of Hammond and Chakraborty, there are now 12 Institute Professors, as well as 10 Institute Professors Emeriti. The new appointments will take effect July 1.

Arup K. Chakraborty

Chakraborty, a chemical engineer by training, has wide-ranging research interests that span biology, chemistry, and physics. His work in immunology has led to discoveries pertinent to T cell activation, the nature of human T cell repertoires, and antibody and T cell responses to infection and vaccination. He has also contributed to the development of potential new vaccines for highly mutable pathogens such as HIV.

“Arup has made seminal contributions in creatively addressing complex interdisciplinary issues at the confluence of molecular engineering, theoretical immunology, and the physical sciences, resulting in — as just one of many examples — advances toward the development of a vaccine for HIV,” Schmidt and Danheiser wrote in their announcement.

At the University of California at Berkeley, where he began his faculty career, Chakraborty pioneered the integration of quantum chemical calculations with macroscopic approaches in chemical engineering. For over two decades, much of his work has focused on developing and applying approaches rooted in statistical physics to tackle questions in immunology.

“Over 20 years ago, I had a hunch, which proved to be correct, that the convergence of physics-based theoretical/computational approaches and experimental immunology would lead to a deep understanding of how the immune system functions, and this knowledge could be harnessed to advance health,” says Chakraborty, who joined the MIT faculty in 2005. “I have truly enjoyed working with basic and clinical immunologists, as well as physicists, chemists, and engineers.”

His work with immunologists led to discoveries such as how the immune synapse functions during T cell activation, how T cells respond to minute numbers of antigens, and why such responses are “on” or “off.” With MIT professor of physics Mehran Kardar, he provided new insights on how developmental processes shape a T cell repertoire that can mount pathogen-specific responses to a diverse and evolving world of microbes.

This work also led to new insights (with Bruce Walker, director of the Ragon Institute) of why humans with certain genes can control HIV infections more efficiently while also being prone to autoimmune diseases. Chakraborty’s work on virus evolution and T cell and antibody responses to infection and vaccination (with professor of biological engineering Darrell Irvine and others) has led him to design novel immunogens for the T cell component of an HIV vaccine that is now in preclinical trials.

Chakraborty’s work with Institute Professor Phillip Sharp and professor of biology Richard Young led to the discovery that the transcription of genes key for maintaining cell identity (such as heart cell, cancer cell, etc.) is regulated by the formation of phase-separated bodies that are now called “transcriptional condensates.”

Chakraborty is the Robert T. Haslam Professor of Chemical Engineering and a professor in the departments of physics and chemistry. One of his most significant strengths, according to the colleagues who nominated him, is his ability to foster collaborations across many different departments.

As the founding director of MIT’s Institute for Medical Engineering and Science, Chakraborty worked to enhance interdisciplinary collaborations between MIT researchers working in life sciences, physical sciences, engineering, and medicine, as well as to establish ongoing partnerships with medical institutions in the Boston area.

“I felt that if I could help catalyze these pan-MIT efforts and help bring new faculty and students to MIT, it would be worth devoting significant effort toward this goal,” Chakraborty says. “I think that IMES enhances MIT’s efforts to bring disciplines together in an integrative way to advance health, and helps educate students who can work seamlessly across disciplines.”

He has also passed that interdisciplinary spirit on to the students and postdocs he mentors: Twenty-four of Chakraborty’s former trainees are now faculty members at various universities, in departments that include chemical engineering, mechanical engineering, physics, chemistry, and immunology. Chakraborty has also received five awards for classroom teaching, and he co-authored a recent book meant for a general audience called “Viruses, Pandemics, and Immunity.”

Chakraborty is a founding steering committee member of the Ragon Institute of MGH, MIT, and Harvard, whose mission is to harness the immune system to cure and prevent disease. He has served on the Defense Science Board of the U.S. Department of Defense since 2013, is a member of the board of governors of the Wellcome Trust, and serves on corporate scientific advisory boards and National Academy panels.

Chakraborty, who grew up in India, earned his bachelor’s degree in chemical engineering from the Indian Institute of Technology Kanpur, then earned a PhD in chemical engineering from the University of Delaware. He was a postdoc at the University of Minnesota before he began his faculty career.

Being named an Institute Professor is the most meaningful recognition he has received, because it comes from his MIT colleagues, Chakraborty says.

“When I look at the list of past and present Institute Professors, I’m deeply humbled and I hope that I can live up to the trust that MIT has placed in me,” he says. “This recognition really belongs to my inspiring faculty colleagues, the students in my classrooms whose immense curiosity makes me a better teacher, and the students and postdocs in my research group who have taught me so much.”

Paula Hammond

Hammond, who is the David H. Koch Professor of Engineering and a member of the Koch Institute for Integrative Cancer Research, is renowned for her work developing polymers and nanomaterials for a variety of applications in drug delivery, noninvasive imaging, solar cells, and battery technology.

“Paula is a pioneer in nanotechnology research and has made substantial contributions to the science and engineering of macromolecular systems, with applications ranging from non-invasive imaging technologies for cancer diagnosis to sustainable solutions for battery technology,” Schmidt and Danheiser wrote in their announcement.

Early in her career, Hammond developed new techniques for building polymers with highly controlled architectures. This approach, known as layer-by-layer assembly, allows polymer layers with different properties to be laid down by alternately exposing a surface to positively and negatively charged particles.

Hammond has used layer-by-layer assembly to develop novel polymers for a variety of medical applications. Some of her polymer nanoparticles  zoom in on tumors and release their cargo when they enter the tumor’s acidic environment, and she has also developed nanoparticles and thin polymer films that can carry multiple drugs to a specific site and release the drugs in a controlled fashion.

In her energy-related work, she has developed polymer films that dramatically improve the efficiency of methanol fuel cells. She is also working on batteries and solar cells that self-assemble with the help of genetically engineered viruses.

After earning her bachelor’s degree from MIT, Hammond spent two years working as a process engineer. During that time, she also earned a master’s degree at Georgia Tech and decided that she wanted to return to academia. She was drawn back to MIT to study for a PhD in part because of the unique drive and enthusiasm she had seen in the students and faculty there.

“There’s a sense at MIT that almost anything can happen if you bring the right people together,” she says. “It has always been exciting to me to work with others who are equally enthusiastic and completely gung-ho about exploring new areas and new ideas, and also about impacting the world with their science.”

After finishing her PhD in polymer science and technology, she was a postdoc at Harvard University before joining MIT’s faculty in 1995. She has been a full professor since 2006.

In their announcement, Schmidt and Danheiser also cited Hammond’s commitment to mentoring future generations of chemical engineers. She has mentored more than 60 graduate students and 60 postdocs during her time as a professor, and has hosted more than 100 undergraduate researchers in her lab. As a reflection of her excellence in teaching and mentoring, Hammond was awarded the MIT Committed to Caring Award in 2017-18, the Henry Hill Lecturer Award in 2002, and the Junior Bose Faculty Award in 2000.

Hammond cited her own mentors at MIT as an inspiration for her devotion to her students.

“I had wonderful mentoring experiences myself when I was a graduate student, and experiencing those kinds of mentors inspired me to give that back to other students,” she says. “I want to be someone who is able to think up new ideas that get me really excited about science, and then to work with young people who are developing their careers to make those ideas real. Even more inspiring is watching them formulate their own ideas in the process, and ultimately seeing them launch their own careers.”

Hammond has also chaired or co-chaired two committees that contributed landmark reports on gender and race at MIT: the Initiative for Faculty Race and Diversity, and the Academic and Organizational Relationships Working Group. She is also a national leader outside of MIT, and has served on the U.S. Secretary of Energy Scientific Advisory Board, the NIH Center for Scientific Review Advisory Council, and the Board of Directors of the American Institute of Chemical Engineers.

In 2019, Hammond was awarded the American Institute of Chemical Engineers Margaret H. Rousseau Pioneer Award for Lifetime Achievement by a Woman Chemical Engineer. She also received the ETH Zurich Chemical Engineering Medal in 2019 and the American Chemical Society Award in Applied Polymer Science in 2018.

In recognition of their achievements, both Hammond and Chakraborty have been elected to all three National Academies — Engineering, Science, and Medicine — making them two of only 25 people to hold that distinction.

“It’s a real honor to become an Institute Professor alongside Arup, who has always been such a universal contributor,” Hammond says. “I’ve always thought of this group as just amazing, incredible people because of the things that they’ve done. Each Institute Professor is at the cutting edge of their field and they’ve also done great things for MIT. When I look at the list of current and past Institute Professors, I am both extremely humbled and greatly inspired by their achievements and impact on MIT and the greater world. I’m very honored to be among this group.”

Five from MIT elected to the National Academy of Sciences for 2021

by Sandi Miller | Department of Mathematics |

The National Academy of Sciences has elected 120 new members and 30 international associates, including five professors from MIT — Dan Freedman, Robert Griffin, Larry Guth, Stephen Morris, and Gigliola Staffilani — in recognition of their “distinguished and continuing achievements in original research.” Current membership totals 2,461 active members and 511 international associates. Membership is one of the highest honors that a scientist can achieve.

The National Academy of Sciences is a private, nonprofit institution that was established under a congressional charter signed by President Abraham Lincoln in 1863. It recognizes achievement in science by election to membership, and — with the National Academy of Engineering and the National Academy of Medicine — provides science, engineering, and health policy advice to the federal government and other organizations.

Daniel Freedman

Daniel Freedman, professor emeritus in MIT’s departments of Mathematics and Physics, is also a visiting professor at Stanford University’s Institute for Theoretical Physics. Freedman’s research is in quantum field theory, quantum gravity, and string theory, with an emphasis on the role of supersymmetry. More recently, one focus of his work is the AdS/CFT correspondence, a broad framework based on the equivalence of field theories in different spacetime dimensions, one with and one without gravity.

He received his BA from Wesleyan University in 1960, and his MS and PhD in physics from the University of Wisconsin in 1962 and 1964. Freedman held postdoctoral appointments at Imperial College, the University of California at Berkeley, and Princeton University before joining the faculty at the Institute of Theoretical Physics at SUNY Stony Brook. In 1980 he joined the MIT faculty in applied mathematics, and has been jointly appointed with the MIT theoretical physics faculty since 2001.

Freedman was a distinguished alumni fellow at the University of Wisconsin-Madison, was a former Sloan and Guggenheim fellow, and was named Fellow of the American Academy of Arts and Sciences and of the American Physical Society. He has received the Special Breakthrough Prize in Fundamental Physics, the Dirac Medal and Prize, and the Dannie Heineman Prize.

Robert Guy Griffin

Robert Guy Griffin, the Arthur Amos Noyes Professor of Chemistry, is also director of the Francis Bitter Magnet Laboratory. He devotes a large fraction of the Griffin Group’s research efforts to develop new magnetic resonance techniques to study molecular structure and dynamics. He also develops high-field dynamic nuclear polarization for the study of biological solids.

Griffin received his BS in 1964 from the University of Arkansas, and his PhD from Washington University in 1969. He joined the Francis Bitter Magnet Laboratory in 1972, and the Department of Chemistry’s faculty in 1989.

He was awarded the Richard R. Ernst Prize in Magnetic Resonance, sponsored by the Bruker BioSpin Corporation, for his pioneering contributions to high-resolution solid-state nuclear magnetic resonance as a whole, as well as its applications to biological systems. In particular, Griffin has developed widely used techniques for dipolar recoupling that permit internuclear distances to be measured during so-called “magic angle” spinning experiments.

He has also received the ISMAR (International Society of Magnetic Resonance) Prize, the Günther Laukien Prize for NMR research, and the Bijvoet Medal of the Bijvoet Center for Biomolecular Research of Utrecht University.

Larry Guth

Claude E. Shannon Professor of Mathematics Larry Guth’s research interests are in metric geometry, with a focus on systolic inequality, and on finding connections between geometric inequalities and topology. More recently, Guth has been researching harmonic analysis and combinatorics, in relation to the Kakeya problem, an open question in Euclidean geometry that connects with restriction-type estimates in Fourier analysis and with estimates about incidences of lines in extremal combinatorics.

Guth received his BS in mathematics from Yale University, and after receiving his PhD from MIT in 2005, he followed a postdoctoral position at Stanford with faculty appointments at the University of Toronto and the Courant. He joined the MIT math faculty in 2012.

Guth received the Salem Prize in Mathematics for outstanding contributions to analysis, the Maryam Mirzakhani Prize in Mathematics, the American Mathematical Society’s Bocher Prize, and the New Horizons in Mathematics Prize. He received the School of Science’s Teaching Prize in Graduate Education, and was named a Margaret MacVicar Faculty Fellow for exceptional undergraduate teaching.

Stephen Morris

Stephen Morris, the Peter A. Diamond Professor in Economics, is an economic theorist who has made important contributions to the foundations of game theory and mechanism design, as well as applications in macroeconomics, international economics, and finance. He has developed new ways of understanding and modeling the role of incomplete information in the economy, and its implications for analysis and policy.

Morris received his undergraduate degree in mathematics and economics at Cambridge University, and his PhD from Yale University. He taught at the University of Pennsylvania, Yale University, and Princeton University before joining MIT’s Department of Economics in 2019.

Morris is a fellow and was president of the Econometric Society. He is a member of the American Academy of Arts and Sciences, a research fellow of the Center for Economic Policy Research, and was a Sloan Research and Guggenheim Fellow.

Gigliola Staffilani

Gigliola Staffilani, the Abby Rockefeller Mauzé Professor of Mathematics, is a mathematical analyst whose research focuses on dispersive nonlinear partial differential equations. She is one of 59 new members who are women, the most elected to the NAS in a single year.

Staffilani received the BS equivalent from the University of Bologna in 1989, and MS and PhD degrees from the University of Chicago in 1991 and 1995. She held positions at Princeton, Stanford, and Brown universities, and joined MIT in 2002.

She is a member of the Massachusetts Academy of Sciences, the American Academy of Arts and Sciences, and the National Academy of Sciences. She received a Guggenheim Fellowship and a Simons Fellowship in Mathematics, and is a fellow of the American Mathematical Society. At MIT, she received the inaugural MITx Prize for Teaching and Learning in MOOCs by the MIT Office of Digital Learning, the Earll M. Murman Award for Excellence in Undergraduate Advising, and the “Committed to Caring” award by the Office of Graduate Education.

Mastering molecular disorder

by Anne Trafton | MIT News Office |

Some materials, including metals, consist of atoms densely packed in a lattice or crystal. These structures can be very good at conducting electricity, and their behavior is often relatively easy to predict. Other materials, such as plastics and other polymers, have a great deal of disorder to their structures.

Adam Willard, an associate professor of chemistry at MIT, wants to illuminate those disordered structures. Using theoretical models and high-powered supercomputers, he is developing ways to simulate the properties of these disordered materials and predict their behavior. This kind of modeling could help researchers replace heavy and brittle silicon-based photovoltaic cells with light and flexible alternatives made entirely of plastic.

“Our interest is really in trying to understand the role of molecular disorder in physical processes that are important in both biology and the energy sciences,” says Willard, who recently earned tenure in MIT’s Department of Chemistry. “We want to develop a deeper understanding of how molecular forces play a role in the chemical processes that are fundamental to life and industry.”

Captivated by chemistry

Growing up in Bend, Oregon, Willard wanted to become a doctor and entered the University of Puget Sound in Tacoma, Washington, as a pre-med major. However, by the end of his sophomore year, he had lost his enthusiasm for medicine and decided to switch to a double major in chemistry and math.

“Fortuitously, the next course I had to take was an undergraduate course in quantum mechanics in the chemistry department, and I loved it,” Willard recalls. “I decided then that being a chemistry professor would be a pretty nice gig because the material was so deep and captivating.”

Having switched his major late, Willard hadn’t done much chemistry research as an undergraduate, so he decided to spend a year after graduation working in an experimental spectroscopy lab at the University of Puget Sound. “It was a great experience because I got to have a spectrometer all to myself, and I got to spend late nights alone in the lab, collecting data and thinking about things. I enjoyed it immensely,” he says.

He attended graduate school at the University of California at Berkeley, drawn by its program in theoretical chemistry. There, he used computer simulations to study how hydrophobic forces between large molecules influence their behavior, as well as how water affects the interactions between such molecules.

After finishing his PhD, Willard went to the University of Texas at Austin to do a postdoc studying quantum dynamics, specifically those seen in organic photovoltaics — solar cells made from plastic. Such cells are lightweight, easy to make, and relatively inexpensive. However, at the molecular scale, these plastics are made of many tangled strands, which present complex pathways for the transport of electrons.

Much of Willard’s work in this area, which has continued since he joined MIT’s faculty in 2013, focuses on designing materials that will allow electrons to efficiently flow from one site, where they are excited by light, to the point where their energy is collected.

“For photovoltaic applications, we want to arrange photoexcitable molecules in a particular geometry, so that if we excite one molecule, the excited electron is passed through the material, molecule to molecule, in a way that guides and transforms them in predictable ways,” he says.

Watery environments

In his lab at MIT, Willard has also continued studying interactions between water and other molecules. While he focused on hydrophobic interactions as graduate student, he now analyzes hydrophilic molecules and how they interact with each other in water.

“Describing how hydrophilic objects interact with each other in water is much more complicated because there are many different ways that surfaces can be hydrophilic, whereas there’s only one way to be hydrophobic. So, if I’ve solved the hydrophobic problem for one case, I’ve solved it for all of the cases. However, the behavior of hydrophilic particles depends very much on how they are hydrophilic, for example, positively and negatively charged surfaces have different influences on the surrounding water,” Willard says.

Some important types of hydrophilic interactions include protein-protein interactions and protein-drug interactions. These molecules often form weak hydrogen bonds that help hold them together. Water can affect these bonds, influencing the binding strength between two proteins or a protein and a drug.

In the last few years, Willard’s research group has developed computational methods to analyze the hydration environment surrounding a protein and how it depends on a protein’s conformation. They are now using machine-learning techniques, similar to those used to teach computer models to recognize objects, to identify sites of a protein that could be targeted by particular drugs.

Another area of research in his lab involves interactions that occur at surfaces where electrochemical reactions take place, such as those found in batteries. These interactions are typically difficult to simulate because describing the path of electrons within the electrodes requires massive computational resources, but Willard’s lab has developed methods to make this description more efficient. This kind of modeling could help to researchers to design better battery or electrocatalytic systems.

“Our hope is that our contributions will provide both new fundamental theory that will help people understand these systems better, but also in specific cases, provide molecular design principles that can be applied,” Willard says.

Synthetic gelatin-like material mimics lobster underbelly’s stretch and strength

by Jennifer Chu | MIT News Office |

A lobster’s underbelly is lined with a thin, translucent membrane that is both stretchy and surprisingly tough. This marine under-armor, as MIT engineers reported in 2019, is made from the toughest known hydrogel in nature, which also happens to be highly flexible. This combination of strength and stretch helps shield a lobster as it scrabbles across the seafloor, while also allowing it to flex back and forth to swim.

Now a separate MIT team has fabricated a hydrogel-based material that mimics the structure of the lobster’s underbelly. The researchers ran the material through a battery of stretch and impact tests, and showed that, similar to the lobster underbelly, the synthetic material is remarkably “fatigue-resistant,” able to withstand repeated stretches and strains without tearing.

If the fabrication process could be significantly scaled up, materials made from nanofibrous hydrogels could be used to make stretchy and strong replacement tissues such as artificial tendons and ligaments.

The team’s results are published today in the journal Matter. The paper’s MIT co-authors include postdocs Jiahua Ni and Shaoting Lin; graduate students Xinyue Liu and Yuchen Sun; professor of aeronautics and astronautics Raul Radovitzky; professor of chemistry Keith Nelson; mechanical engineering professor Xuanhe Zhao; and former research scientist David Veysset PhD ’16, now at Stanford University; along with Zhao Qin, assistant professor at Syracuse University, and Alex Hsieh of the Army Research Laboratory.

Nature’s twist

In 2019, Lin and other members of Zhao’s group developed a new kind of fatigue-resistant material made from hydrogel — a gelatin-like class of materials made primarily of water and cross-linked polymers. They fabricated the material from ultrathin fibers of hydrogel, which aligned like many strands of gathered straw when the material was repeatedly stretched. This workout also happened to increase the hydrogel’s fatigue resistance.

“At that moment, we had a feeling nanofibers in hydrogels were important, and hoped to manipulate the fibril structures so that we could optimize fatigue resistance,” says Lin.

In their new study, the researchers combined a number of techniques to create stronger hydrogel nanofibers. The process starts with electrospinning, a fiber production technique that uses electric charges to draw ultrathin threads out of polymer solutions. The team used high-voltage charges to spin nanofibers from a polymer solution, to form a flat film of nanofibers, each measuring about 800 nanometers — a fraction of the diameter of a human hair.

They placed the film in a high-humidity chamber to weld the individual fibers into a sturdy, interconnected network, and then set the film in an incubator to crystallize the individual nanofibers at high temperatures, further strengthening the material.

They tested the film’s fatigue-resistance by placing it in a machine that stretched it repeatedly over tens of thousands of cycles. They also made notches in some films and observed how the cracks propagated as the films were stretched repeatedly. From these tests, they calculated that the nanofibrous films were 50 times more fatigue-resistant than the conventional nanofibrous hydrogels.

nanofibrous structure

Around this time, they read with interest a study by Ming Guo, associate professor of mechanical engineering at MIT, who characterized the mechanical properties of a lobster’s underbelly. This protective membrane is made from thin sheets of chitin, a natural, fibrous material that is similar in makeup to the group’s hydrogel nanofibers.

Guo found that a cross-section of the lobster membrane revealed sheets of chitin stacked at 36-degree angles, similar to twisted plywood, or a spiral staircase. This rotating, layered configuration, known as a bouligand structure, enhanced the membrane’s properties of stretch and strength.

“We learned that this bouligand structure in the lobster underbelly has high mechanical performance, which motivated us to see if we could reproduce such structures in synthetic materials,” Lin says.

Angled architecture

Ni, Lin, and members of Zhao’s group teamed up with Nelson’s lab and Radovitzky’s group in MIT’s Institute for Soldier Nanotechnologies, and Qin’s lab at Syracuse University, to see if they could reproduce the lobster’s bouligand membrane structure using their synthetic, fatigue-resistant films.

“We prepared aligned nanofibers by electrospinning to mimic the chinic fibers existed in the lobster underbelly,” Ni says.

After electrospinning nanofibrous films, the researchers stacked each of five films in successive, 36-degree angles to form a single bouligand structure, which they then welded and crystallized to fortify the material. The final product measured 9 square centimeters and about 30 to 40 microns thick — about the size of a small piece of Scotch tape.

Stretch tests showed that the lobster-inspired material performed similarly to its natural counterpart, able to stretch repeatedly while resisting tears and cracks — a fatigue-resistance Lin attributes to the structure’s angled architecture.

“Intuitively, once a crack in the material propagates through one layer, it’s impeded by adjacent layers, where fibers are aligned at different angles,” Lin explains.

The team also subjected the material to microballistic impact tests with an experiment designed by Nelson’s group. They imaged the material as they shot it with microparticles at high velocity, and measured the particles’ speed before and after tearing through the material. The difference in velocity gave them a direct measurement of the material’s impact resistance, or the amount of energy it can absorb, which turned out to be a surprisingly tough 40 kilojoules per kilogram. This number is measured in the hydrated state.

steel peircing

“That means that a 5-millimeter steel ball launched at 200 meters per second would be arrested by 13 millimeters of the material,” Veysset says. “It is not as resistant as Kevlar, which would require 1 millimeter, but the material beats Kevlar in many other categories.”

It’s no surprise that the new material isn’t as tough as commercial antiballistic materials. It is, however, significantly sturdier than most other nanofibrous hydrogels such as gelatin and synthetic polymers like PVA. The material is also much stretchier than Kevlar. This combination of stretch and strength suggests that, if their fabrication can be sped up, and more films stacked in bouligand structures, nanofibrous hydrogels may serve as flexible and tough artificial tissues.

“For a hydrogel material to be a load-bearing artificial tissue, both strength and deformability are required,” Lin says. “Our material design could achieve these two properties.”

This research was supported, in part, by MIT and the U. S. Army Research Office through the Institute for Soldier Nanotechnologies at MIT.

School of Science announces 2021 Infinite Mile awards

by School of Science |

The MIT School of Science has recognized 13 staff members with the 2021 Infinite Mile Award.

Staff are nominated for Infinite Mile Awards, presented annually since their creation in 2001, by their peers for going above and beyond in their roles and making MIT a better place. Their support for the School of Science, and the Institute community as a whole, has been invaluable, especially as we pass the one-year mark of work-from-home and social distancing due to the Covid-19 pandemic.

The following are the 2021 School of Science Infinite Mile winners.

  • Rebecca Chamberlain, administrative officer in the Department of Biology, was nominated by Professor Stephen Bell because Chamberlain “makes things easier for everyone in the department and this has never been more true than in this trying year. Even as she has taken on so much more, she has continued to maintain a friendly, patient, and unflappable attitude that makes her all the more remarkable.”
  • Janice Chang, academic administrator in the Department of Biology, was nominated by MIT Human Resources administrator Helene Kelsey because Chang is “truly exceptional, strives for perfection, and her skills and work ethic are recognized throughout the department. Janice has embraced the associated challenges with wisdom, a common-sense approach, dedication, goodwill, and a willingness to devote endless additional hours to the tasks at hand.”
  • Emma Dunn, undergraduate programs assistant in the Department of Physics, was nominated by Academic Administrator Catherine Modica because, when campus closed, “it was Emma who came up with all the ideas we used to try to reach out to our students, […] tracking their arrivals at home to make sure they were safe, and creating and sending shipments of care packages to every undergraduate major to remind them that we were […] thinking about them and standing ready to help.”
  • Jennifer Fentress, communications officer in the Department of Earth, Atmospheric and Planetary Sciences, was nominated by professor of physics and department head Robert van der Hilst; associate professor of physics David McGee; and staff colleagues Julia Keller, Megan Jordan, Angela Ellis, Maggie Cedarstrom, Brandon Milardo, and Scott Wade because Fentress “has helped advance the work of the school and MIT more broadly. At every opportunity, she ensures that the voices of EAPS research scientists are well-represented.”
  • Laura Frawley, a lecturer in the Department of Brain and Cognitive Sciences, was nominated by Professor Michale Fee and staff colleagues Kate White and Kimberli DeMayo because Frawley “has dedicated so much time and effort into learning all the new tools and resources available to help faculty convert to remote learning. […] All in all, Laura has been a savior this year!”
  • Brittany Greenough, an events planning assistant in the Picower Institute for Learning and Memory, was nominated by Picower Institute director and professor of brain and cognitive sciences Li-Huei Tsai and Administrative Officer William Lawson because, “[i]n this new, virtual environment, Brittany has taken it upon herself to be the resident expert with transitioning events to online formats.”
  • Chhayfou Hong, a financial assistant in the Laboratory for Nuclear Science, was nominated by professors of physics Jesse Thaler, Mike Williams, Joseph Formaggio, and Philip Harris because “without Chai’s herculean efforts here, the IAIFI [NSF AI Institute for Artificial Intelligence and Fundamental Interactions] would not exist, and MIT would have missed out on housing one of the inaugural NSF AI institutes — and on $20 million in revenue over the next five years.”
  • Beverly La Marr, a test engineer in the MIT Kavli Institute for Astrophysics and Space Research, was nominated by Kavli Institute director and professor of physics Robert Simcoe and principal research scientists Marshall Bautz, Ronald Remillard, and Gregory Prigozhin because La Marr “has played an essential part in MKI’s success in space with flagships, mid-sized, and small missions; and in fact, at this moment, three missions bearing her intellectual ‘fingerprints’ are all producing exciting scientific data from space. Her contributions to her colleagues are no less significant.”
  • Brian Pretti, a facilities and operations administrator in the Department of Chemistry, was nominated by professor and department head Troy Van Voorhis and administrative officer Richard Wilk because Pretti “is someone who goes far above and beyond his usual call of duty. He is also a joy to work with, no matter the stress or difficulty of the situation. Brian exemplifies all of the qualities of someone who truly cares about the quality of his work and those individuals he supports. He has demonstrated an incredible commitment to the Department, and it is a better place because of him.”
  • Alison Salie, senior fiscal officer in the Department of Biology, was nominated by professor and department head Alan Grossman because Salie “is a top-notch employee, well-respected across the department and Institute, and valued for her knowledge and expertise, common-sense approach, willingness to provide support and guidance at every turn, persistence, and never-ending goal to keep work flowing smoothly with limited administrative burden on faculty.”
  • Amanda Trainor, a technical associate in the Department of Chemistry, was nominated by colleagues John Dolhun, Brian Pretti, Scott Ide, John Grimes, and graduate student Axel Vera because her “work on all aspects of various lab functions has been outstanding, from finishing her assigned responsibilities, to taking on unassigned work that needed to be done, [and] demonstrating a strong commitment to the well-being of the MIT community by going countless extra miles.”
  • Joshua Wolfe, a technical instructor in the Department of Physics, was nominated by postdoc Alex Shvonski and lecturer Michelle Tomasik because Wolfe “goes above and beyond his prescribed duties because he cares holistically about creating an effective learning environment in our classes.”
  • Macall Zimmerman, senior financial officer in the Department of Chemistry, was nominated by professor and department head Troy Van Voorhis and staff colleagues Richard Wilk and Tyler Brezler because Zimmerman “is someone who goes far above and beyond her usual call of duty. She is an excellent leader, manager, and mentor. She demonstrates an exceptional commitment to every aspect of her work and the staff whom she mentors. Our department is a better place with her in it.”

The 2021 Infinite Mile Award winners receive a monetary award. An in-person celebration will be held in their honor, as well as the 2021 Infinite Expansion Award winners, at a later date with their families, friends, and nominators.

Synthetic mucus can mimic the real thing

by Anne Trafton | MIT News Office |

More than just a sign of illness, mucus is a critical part of our body’s defenses against disease. Every day, our bodies produce more than a liter of the slippery substance, covering a surface area of more than 400 square meters to trap and disarm microbial invaders.

Mucus is made from mucins — proteins that are decorated with sugar molecules. Many scientists are trying to create synthetic versions of mucins in hopes of replicating their beneficial traits. In a new study, researchers from MIT have now generated synthetic mucins with a polymer backbone that more accurately mimic the structure and function of naturally occurring mucins. The team also showed that these synthetic mucins could effectively neutralize the bacterial toxin that causes cholera.

The findings could help give researchers a better idea of which features of mucins contribute to different functions, especially their antimicrobial functions, says Laura Kiessling, the Novartis Professor of Chemistry at MIT. Replicating those functions in synthetic mucins could eventually lead to new ways to treat or prevent infectious disease, and such materials may be less likely to lead to the kind of resistance that occurs with antibiotics, she says.

“We would really like to understand what features of mucins are important for their activities, and mimic those features so that you could block virulence pathways in microbes,” says Kiessling, who is the senior author of the new study.

Kiessling’s lab worked on this project with Katharina Ribbeck, the Mark Hyman, Jr. Career Development Professor of Biological Engineering, and Richard Schrock, the F.G. Keyes Professor Emeritus of Chemistry, who are also authors of the paper. The lead authors of the paper, which appears today in ACS Central Science, are former MIT graduate student Austin Kruger and MIT postdoc Spencer Brucks.

Inspired by mucus

Kiessling and Ribbeck joined forces to try to create mucus-inspired materials in 2018, with funding from a Professor Amar G. Bose Research Grant. The primary building blocks of mucus are mucins — long, bottlebrush-like proteins with many sugar molecules called glycans attached. Ribbeck has discovered that these mucins disrupt many key functions of infectious bacteria, including their ability to secrete toxins, communicate with each other, and attach to cellular surfaces.

Those features have led many scientists to try to generate artificial versions that could help prevent or treat bacterial infection. However, mucins are so large that it has been difficult to replicate their structure accurately. Each mucin polymer has a long backbone consisting of thousands of amino acids, and many different glycans can be attached to these backbones.

In the new study, the researchers decided to focus on the backbone of the polymer. To try to replicate its structure, they used a reaction called ring-opening metathesis polymerization. During this type of reaction, a carbon-containing ring is opened up to form a linear molecule containing a carbon-carbon double bond. These molecules can then be joined together to form long polymers.

In 2005, Schrock shared the Nobel Prize in Chemistry for his work developing catalysts that can drive this type of reaction. Later, he developed a catalyst that could yield specifically the “cis” configuration of the products. Each carbon atom in the double bond usually has one other chemical group attached to it, and in the cis configuration, both of these groups are on the same side of the double bond. In the “trans” configuration, the groups are on opposite sides.

To create their polymers, the researchers used Schrock’s catalyst, which is based on tungsten, to form cis versions of mucin mimetic polymers. They compared these polymers to those produced by a different, ruthenium-based catalyst, which creates trans versions. They found that the cis versions were much more similar to natural mucins — that is, they formed very elongated, water-soluble polymers. In contrast, the trans polymers formed globules that clumped together instead of stretching out.

Mimicking mucins

The researchers then tested the synthetic mucins’ ability to mimic the functions of natural mucins. When exposed to the toxin produced by Vibrio cholerae, the elongated cis polymers were much better able to capture the toxin than the trans polymers, the researchers found. In fact, the synthetic cis mucin mimics were even more effective than naturally occurring mucins.

The researchers also found that their elongated polymers were much more soluble in water than the trans polymers, which could make them useful for applications such as eye drops or skin moisturizers.

Now that they can create synthetic mucins that effectively mimic the real thing, the researchers plan to study how mucins’ functions change when different glycans are attached to the backbones. By altering the composition of the glycans, they hope to develop synthetic mucins that can dampen virulence pathways of a variety of microbes.

“We’re thinking about ways to even better mimic mucins, but this study is an important step in understanding what’s relevant,” Kiessling says.

In addition to the Bose grant, the research was funded by the National Institute of Biomedical Imaging and Bioengineering, the National Science Foundation, and the National Institute of Allergy and Infectious Diseases.

Cooling homes without warming the planet

by Zach Winn | MIT News Office |

As incomes in developing countries continue to rise, demand for air conditioners is expected to triple by 2050. The surge will multiply what is already a major source of greenhouse gas emissions: Air conditioning is currently responsible for almost 20 percent of electricity use in buildings around the world.

Now the startup Transaera is working to curb those energy demands with a more efficient air conditioner that uses safer refrigerants to cool homes. The company believes its machine could have one-fifth the impact on the climate when compared to traditional ACs.

“The thing about air conditioning is the basic technology hasn’t changed much since it was invented 100 years ago,” says Transaera chief engineer Ross Bonner SM ’20.

That will change rapidly if Transaera’s small team is successful. The company is currently a finalist in a global competition to redesign the air conditioner. The winner of the competition, named the Global Cooling Prize, will get $1 million to commercialize their machines.

At the heart of Transaera’s design is a class of highly porous materials called metal organic frameworks, or MOFs, that passively pull moisture from the air as the machine works. Co-founder Mircea Dincă, the W.M. Keck Professor of Energy in MIT’s Department of Chemistry, has done pioneering research on MOFs, and the company’s team members see the materials’ commercial advancement as an important part of their mission.

“MOFs have a lot of potential applications, but the thing that’s held them back is unit economics and the inability to make them in a cost-effective way at scale,” says Bonner. “What Transaera aims to do is be the first to commercialize MOFs at scale and lead the breakthrough that brings MOFs into the public domain.”

Dincă’s co-founders are Transaera CEO Sorin Grama SM ’07, who is also a lecturer at MIT D-Lab, and CTO Matt Dorson, a mechanical engineer who worked with Grama on a previous startup.

“I’m just incentivized by this idea of creating something revolutionary,” says Grama. “We’ve designed these new devices, but we’re also bringing this material knowledge, with Mircea and our collaborators, and blending the two to create something really new and different.”

A material of opportunity

Grama and Dorson previously collaborated at Promethean Power Systems, which develops off-grid refrigeration solutions for farmers in India. To date, the company has installed 1,800 refrigeration systems that serve roughly 60,000 farmers each day. After stepping down as CEO in 2015, Grama returned to the Institute to teach at MIT D-Lab and serve as an entrepreneur-in-residence at the Martin Trust Center for MIT Entrepreneurship.

During that time Grama was introduced to MOFs by Rob Stoner, the MIT Energy Initiative’s deputy director for science and technology and a founding director of the MIT Tata Center.

Stoner introduced Grama to Dincă, who had been studying MOFs since he joined MIT’s faculty in 2010 and grew up 10 miles from Grama’s hometown in Romania.

MOF’s intriguing properties come from their large internal surface area and the ability to finely tune the size of the tiny chambers that run through them. Dincă previously developed MOFs with chambers just big enough to trap water molecules from the air. He described them as “sponges on steroids.”

Grama began thinking about using the material for refrigeration, but another application soon presented itself. Most people think air conditioners only cool the air in a space, but they also dry the air they’re cooling. Traditional machines use something called an evaporator, a cold coil to pull water out of the air through condensation. The cold coil must be made much colder than the desired temperature in the room in order to collect moisture. Dorson says pulling moisture out of the air takes up about half of the electricity used by traditional air conditioners.

Transaera’s MOFs passively collect moisture as air enters the system. The machine’s waste heat is then used to dry the MOF material for continuous reuse.

Transaera was formally founded in the beginning of 2018, and the Global Cooling Prize was announced later that year. Hundreds of teams expressed interest, and Transaera was ultimately selected as one of eight finalists and given $200,000 to deliver prototypes to competition organizers.

Bonner joined the company in 2019 after exploring paths to carbon neutral ACs as part of a mechanical engineering class at MIT.

When Covid-19 began sweeping through countries around the world, it was decided the Cooling Prize’s trials in India would be run remotely. Adding to the challenge, the co-founders didn’t have access to their lab in Somerville due to restrictions and were using their own tools and garages to complete the prototypes. After shipping off their prototypes, Transaera had to help Prize organizers install them through a live video feed for field trials in multiple locations in India. The team says the results validated Transaera’s approach and showed the system had a significantly lower climate impact than baseline units.

Transaera’s system also used a refrigerant known as R-32 with zero ozone depleting potential (ODP) and a global warming potential about three times lower than another commonly used refrigerant.

The milestone further convinced Transaera’s small team they were onto something.

“This air conditioning problem can have a real, material impact on people’s quality of life,” Dorson says.

Pushing a field forward

The Global Cooling Prize will announce its winner next month. Regardless of what happens, Transaera will be growing the team this year and running additional trials in Boston. The company has been working with large manufacturers that have supplied equipment for prototypes and shown the founders how they might integrate their devices with existing technologies.

The company’s foundational work with MOFs has continued even as Transaera’s air conditioner gets closer to commercialization. In fact, Transaera recently received a grant from the National Science Foundation to explore more efficient paths to MOF production with a lab at MIT.

“MOFs open up so many possibilities for all kinds of revolutionary devices, not just in air conditioning, but in water harvesting, energy storage, and super capacitors,” Grama says. “This knowledge we’re developing can apply to so many other applications down the road, and I feel like we’re pioneering this field and pushing the edge of the technology.”

Still, Transaera’s founders remain focused on bringing their AC to market first, acknowledging the problem they’re trying to tackle is big enough to keep them busy for a while.

“It’s clear when you look at the swath of the world that’s in the hot, humid tropics, there’s a growing middle class, and one of the first thing they’ll want to buy is an air conditioner,” Dorson says. “Developing more efficient air conditioning systems is critical for the health of people and of our planet’s environment.”

Design could enable longer lasting, more powerful lithium batteries

by David L. Chandler | MIT News Office |

Lithium-ion batteries have made possible the lightweight electronic devices whose portability we now take for granted, as well as the rapid expansion of electric vehicle production. But researchers around the world are continuing to push limits to achieve ever-greater energy densities — the amount of energy that can be stored in a given mass of material — in order to improve the performance of existing devices and potentially enable new applications such as long-range drones and robots.

One promising approach is the use of metal electrodes in place of the conventional graphite, with a higher charging voltage in the cathode. Those efforts have been hampered, however, by a variety of unwanted chemical reactions that take place with the electrolyte that separates the electrodes. Now, a team of researchers at MIT and elsewhere has found a novel electrolyte that overcomes these problems and could enable a significant leap in the power-per-weight of next-generation batteries, without sacrificing the cycle life.

The research is reported today in the journal Nature Energy in a paper by MIT professors Ju Li, Yang Shao-Horn, and Jeremiah Johnson; postdoc Weijiang Xue; and 19 others at MIT, two national laboratories, and elsewhere. The researchers say the finding could make it possible for lithium-ion batteries, which now typically can store about 260 watt-hours per kilogram, to store about 420 watt-hours per kilogram. That would translate into longer ranges for electric cars and longer-lasting changes on portable devices.

The basic raw materials for this electrolyte are inexpensive (though one of the intermediate compounds is still costly because it’s in limited use), and the process to make it is simple. So, this advance could be implemented relatively quickly, the researchers say.

The electrolyte itself is not new, explains Johnson, a professor of chemistry. It was developed a few years ago by some members of this research team, but for a different application. It was part of an effort to develop lithium-air batteries, which are seen as the ultimate long-term solution for maximizing battery energy density. But there are many obstacles still facing the development of such batteries, and that technology may still be years away. In the meantime, applying that electrolyte to lithium-ion batteries with metal electrodes turns out to be something that can be achieved much more quickly.

The new application of this electrode material was found “somewhat serendipitously,” after it had initially been developed a few years ago by Shao-Horn, Johnson, and others, in a collaborative venture aimed at lithium-air battery development.

“There’s still really nothing that allows a good rechargeable lithium-air battery,” Johnson says. However, “we designed these organic molecules that we hoped might confer stability, compared to the existing liquid electrolytes that are used.” They developed three different sulfonamide-based formulations, which they found were quite resistant to oxidation and other degradation effects. Then, working with Li’s group, postdoc Xue decided to try this material with more standard cathodes instead.

The type of battery electrode they have now used with this electrolyte, a nickel oxide containing some cobalt and manganese, “is the workhorse of today’s electric vehicle industry,” says Li, who is a professor of nuclear science and engineering and materials science and engineering.

Because the electrode material expands and contracts anisotropically as it gets charged and discharged, this can lead to cracking and a breakdown in performance when used with conventional electrolytes. But in experiments in collaboration with Brookhaven National Laboratory, the researchers found that using the new electrolyte drastically reduced these stress-corrosion cracking degradations.

The problem was that the metal atoms in the alloy tended to dissolve into the liquid electrolyte, losing mass and leading to cracking of the metal. By contrast, the new electrolyte is extremely resistant to such dissolution. Looking at the data from the Brookhaven tests, Li says, it was “sort of shocking to see that, if you just change the electrolyte, then all these cracks are gone.” They found that the morphology of the electrolyte material is much more robust, and the transition metals “just don’t have as much solubility” in these new electrolytes.

That was a surprising combination, he says, because the material still readily allows lithium ions to pass through — the essential mechanism by which batteries get charged and discharged — while blocking the other cations, known as transition metals, from entering. The accumulation of unwanted compounds on the electrode surface after many charging-discharging cycles was reduced more than tenfold compared to the standard electrolyte.

“The electrolyte is chemically resistant against oxidation of high-energy nickel-rich materials, preventing particle fracture and stabilizing the positive electrode during cycling,” says Shao-Horn, a professor of mechanical engineering and materials science and engineering. “The electrolyte also enables stable and reversible stripping and plating of lithium metal, an important step toward enabling rechargeable lithium-metal batteries with energy two times that of the state-the-art lithium-ion batteries. This finding will catalyze further electrolyte search and designs of liquid electrolytes for lithium-metal batteries rivaling those with solid state electrolytes.”

The next step is to scale the production to make it affordable. “We make it in one very easy reaction from readily available commercial starting materials,” Johnson says. Right now, the precursor compound used to synthesize the electrolyte is expensive, but he says,  “I think if we can show the world that this is a great electrolyte for consumer electronics, the motivation to further scale up will help to drive the price down.”

Because this is essentially a “drop in” replacement for an existing electrolyte and doesn’t require redesign of the entire battery system, Li says, it could be implemented quickly and could be commercialized within a couple of years. “There’s no expensive elements, it’s just carbon and fluorine. So it’s not limited by resources, it’s just the process,” he says.

The research was supported by the U.S. Department of Energy and the National Science Foundation, and made use of facilities at Brookhaven National Laboratory and Argonne National Laboratory.