Forbes calls this year's 30 Under 30 lists an "encyclopedia of creative disruption."
mit forbes 30 under 30 2018 Web
At least 30 MIT faculty, research staff, and alumni are listed throughout Forbes’ seventh annual 30 Under 30 edition, featuring some of the world’s best young innovators.

Forbes calls its 2018 30 Under 30 lists an “encyclopedia of creative disruption featuring 600 young stars in 20 different industries.” So it should come as no surprise that these lists are heavily populated by recent MIT graduates and other members of the Institute community.

Similar to past years, at least 30 MIT faculty, research staff, and alumni are listed throughout Forbes’ seventh annual edition of the world’s best young innovators. Read about the MIT community members who made this year’s list below:

Omar Abudayyeh ’12 and Jonathan Gootenberg ’13 (health care), doctoral candidates at the Broad Institute of Harvard and MIT. “Abudayyeh and Gootenberg pioneered two advances: a new enzyme for editing genes and a new technique for editing RNA.”

David Bierman SM ’14, PhD ’17 (energy), founder of Marigold Power, Inc. “At MIT he helped to develop a thermophotovoltaic converter that absorbs sunlight and converts it to a form of light.”

Greg Brockman ’13 (enterprise technology), chief technology officer of OpenAI. “The boundary-breaking nonprofit is dedicated to building safe AI and ensuring AI’s benefits are widely and evenly distributed.”

Ritchie Chen SM ’13, PhD ’16 (science), postdoc at the MIT Institute for Medical Engineering and Science. “Chen’s research found that dysfunctional brain regions could be stimulated by metal nanoparticles powered by magnetic fields.”

Tiffany Chu ’10 (enterprise technology), cofounder of Remix. “Chu is cofounder of Remix, a public transit platform used by more than 200 agencies worldwide…that evaluates transit data and suggests improvements.”

Lisa Conn MBA ’17 (law and policy), strategic partner and manager at Facebook. “Conn joined Facebook to lead the civic leadership team in its community partnerships program. Previously at the MIT Media Lab, Conn was program manager of the Electome Project.”

Cody Daniel ’11 (science), director of research at 3Scan. “Instead of fewer than 10 slices, 3Scan’s … robotic microscope can turn a small tissue sample into up to 60,000 slices.”

Maher Damak SM ’15 and Karim Khalil SM ’14 (energy), cofounders of Infinite Cooling. “Infinite Cooling … recaptures 80 percent of the water vapor that normally escapes from cooling towers attached to big power plants.”

Karen Dubbin ’12 (manufacturing and industry), science director at Aether. “Dubbin is the science director at Aether, which builds 3-D-printers capable of creating living tissue. She’s responsible for creating the 'bio-inks' that Aether uses to build tissues.”

Gregory Falco (enterprise technology), graduate student in the MIT Department of Urban Studies ans Planning and cofounder of NeuroMesh. “NeuroMesh provides endpoint security for smart devices and re-engineers malware to become a vaccine for the Internet of Things.”

Alistair Johnson (health care), postdoc in the MIT Laboratory for Computational Physiology. “Johnson created a database of ICU records used by 4,000 researchers from 30 countries to conduct clinical research.”

Brent Keller PhD ’16 (manufacturing), cofounder of Via Separations. “Via Separations develops membrane materials for separation processes. Keller [is] part of MIT’s The Engine accelerator program.”

Weihua Li ’15, MEng ’16 and Arun Saigal ’13, MEng ’13 (consumer technology), cofounders of Thunkable. “Saigal and Li decided spin-out MIT’s App Inventor tool, the drag-and-drop service for building your own app.”

Karthish Manthiram (science), assistant professor in the MIT Department of Chemical Engineering. “Manthiram’s research is focused on providing farmers with fertilizer by manufacturing it out of thin air, literally, by using air, water, and solar power.”

Jess Newman MBA ’17 (energy), director of U.S agronomy at Anheuser Busch InBev. "Her team of 15 agronomists advise barley, rice, and hop farmers on how to become more efficient."

Christina Qi ’13 and Jonathan Wang ’13, MEng ’15 (finance), partners at Domeyard LP. “[Domeyard] is a small hedge fund that is using high-frequency strategies to trade U.S. equity futures and currencies.”

Ritu Raman (science), postdoc at MIT's Koch Institute for Integrative Cancer Research. “Raman’s research focuses on understanding the dynamic interactions between biological and synthetic materials and developing bio-hybrid systems to tackle different applications. ”

Yichen Shen PhD ’16 (energy), postdoc in the MIT Research Laboratory of Electronics. “Has contributed to nanophotonic breakthroughs that could shape the future of energy. Light-AI designs computer chips powered by light rather than electricity.”

Hao Sun (science), research affiliate in the MIT Department of Civil and Environmental Engineering and assistant professor at the University of Pittsburgh. “Sun’s research uses analytics and machine learning combined with internet-of-things enabled sensors to track the health of buildings.”

Scott Sundvor ’12 (consumer technology), cofounder of Nima. “Nima is a portable bluetooth-enabled device that tests foods for allergens before you eat. The company has raised more than $20 million between venture funding and government grants.”

Michael Tomovich SM ’14 (manufacturing), cofounder of Kuvee. “Kuvee has engineered a patented, smart wine bottle that prevents oxygen from reaching the wine inside, and has raised $10 million in venture funding to roll it out.”

Sin Wang SM ’15 (science), cofounder of TetraScience. “Wang is cofounder and CTO of TetraScience, which is bringing the internet of things to daily lab work. The company has raised over $10 million in venture capital.”

Andrew Warren PhD ’16 (health care), founding scientist at Glympse Bio. “Based on Andrew Warren’s PhD at MIT, Glympse Bio uses modular nanoparticle sensors to create diagnostics for diseases potentially including cancer. ”

You Wu SM ’14 (manufacturing), cofounder of Pipeguard Robotics. “Wu’s company, Pipeguard Robotics, manufactures a shuttlecock-shaped robot that travels through water pipes to detect leaks.”

Jenny Xu ’19 (games), founder of JCSoft Inc. “Xu has released nine mobile games that have been downloaded over 3.5 million times, including Can You Escape Fate.”

Julia Yu ’10 (finance), investment analyst at Millennium Management. “Emerging markets trader with big role on a large macro team at billionaire Israel Englander’s $34 billion hedge fund.”

A version of this article originally appeared on the Slice of MIT blog.

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Jay London | MIT Alumni Association 
November 21, 2017
MIT News 

More than half of Roxbury, Bunker Hill, students who get summer lab experience at MIT go on to earn a four-year degree.
Susan Rosevear Fall 2017 MRS 0541 DP Web
Community college students who experience a summer of research at MIT develop greater self-confidence and better academic skills, with a majority completing a four-year degree, MIT Materials Research Laboratory Education Officer Susan Rosevear told a symposium at the Materials Research Society Fall meeting in Boston on Monday, Nov. 27, 2017. Photo, Denis Paiste, MIT MRL

A summer of research at MIT gives inner-city Boston community college students a pathway toward greater self-confidence, better academic skills and a four-year college degree, MIT Materials Research Laboratory Education Officer Susan Rosevear said Monday, Nov. 27, 2017, during a symposium at the Materials Research Society [MRS] Fall meeting in Boston.

“Many of them have barely heard about materials science when they come to MIT, and by the end of the summer, they get sort of a full dunk into the world of materials science, so they are better informed to go forward,” Rosevear says. Over the past dozen years, 63 students from Roxbury and Bunker Hill Community Colleges have participated in the program at MIT. Of these, 45 went on to earn a four-year degree, with 34 pursuing degrees in science or engineering. Five continued on to graduate school in science or medicine.

The Research Experience for Undergraduates (REU) program is primarily funded through the MIT Materials Research Laboratory’s National Science Foundation-funded Materials Research Science and Engineering Center [NSF-MRSEC]. Bringing in underrepresented, or non-traditional, students from the community colleges broadens the diversity of students in the REU program.

“We are trying, and I think succeeding, in providing opportunities to community college students that they don’t have at their home institutions,” Rosevear says. Students learn to use electron microscopes, X-ray diffraction spectrometers and other advanced materials science characterization tools. Rosevear addressed a session at MRS highlighting collaborations between community colleges and four-year colleges.

In 2005, the MIT MRSEC, then part of the Center for Materials Science and Engineering, began the partnership with Roxbury Community College with seven students participating during its first year. In recent years, the summer program expanded to include community college professors in materials research on campus led by MIT faculty. So far, nine community college professors have participated. CMSE merged in October 2017 with the Materials Processing Center to form the MIT Materials Research Laboratory.

During the fall 2017 semester, Roxbury Community College Chemistry and Biotechnology Professor Kimberly Stieglitz offered a new course at Roxbury Community College, Research Science, [SCI 281] that brought students to the X-ray diffraction facility at MIT to examine their lab samples. “We keep finding new ways to leverage this partnership,” Rosevear says. Stieglitz and other teachers who have participated in the summer teachers’ program at MIT, also have incorporated material from their summer research into their classroom teaching, Rosevear notes.

Students must complete a basic engineering or science course, such as chemistry or biology, to be accepted into the MIT summer program. Community college teachers select the students based on academic record, statements of interest and faculty letters of recommendation. “They’ve been great partners for us, which is really key to the whole thing,” Rosevear explains. “Kimberly [Stieglitz] has told me, once they are selected, just knowing they are going to MIT changes their performance, they become more serious about themselves, their performance, motivation increases, and they have an increased commitment to STEM,” Rosevear says.

CMSE Scholar Kimberly Stieglitz Jode Lavine 9157 DP Web
Roxbury Community College Chemistry and Biotechnology Professor Kimberly Stieglitz [left] discusses her summer research at MIT with JoDe M. Lavine, Bunker Hill Community College Professor and Chairperson of the Engineering & Physical Sciences Department, during the annual Summer Scholars Poster Session on Aug. 3, 2017. Stieglitz worked in the lab of AMAX Career Development Assistant Professor in Materials Science and Engineering Robert J. Macfarlane. Photo, Denis Paiste, MIT MRL.

Over the course of the summer, community college students attend weekly luncheon meetings covering topics such as crafting a high-quality poster presentation, applying to graduate school, understanding patents and trademarks, and pursuing careers in materials science and other engineering fields.

Interest among MIT faculty in hosting community college students continues to grow. “I have people coming to me and say, how do I get one of these students?
The students have sold themselves, is essentially what’s happened,” Rosevear says.

The community college program is distinct from the Summer Scholars program, which is open to undergraduates in science and engineering from across the U.S. and Puerto Rico who are citizens or legal residents. Applications for summer 2018 must be submitted by Feb. 16, 2018.

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Denis Paiste, MIT Materials Research Laboratory
December 19, 2017

The silent, lightweight aircraft doesn’t depend on fossil fuels.

Since the first airplane took flight over 100 years ago, virtually every aircraft in the sky has flown with the help of moving parts such as propellers, turbine blades, or fans that produce a persistent, whining buzz.

Now MIT engineers have built and flown the first-ever plane with no moving parts. Instead of propellers or turbines, the light aircraft is powered by an “ionic wind” — a silent but mighty flow of ions that is produced aboard the plane, and that generates enough thrust to propel the plane over a sustained, steady flight.

Unlike turbine-powered planes, the aircraft does not depend on fossil fuels to fly. And unlike propeller-driven drones, the new design is completely silent.

“This is the first-ever sustained flight of a plane with no moving parts in the propulsion system,” says Steven Barrett, associate professor of aeronautics and astronautics at MIT. “This has potentially opened new and unexplored possibilities for aircraft which are quieter, mechanically simpler, and do not emit combustion emissions.”

He expects that in the near-term, such ion wind propulsion systems could be used to fly less noisy drones. Further out, he envisions ion propulsion paired with more conventional combustion systems to create more fuel-efficient, hybrid passenger planes and other large aircraft.

Barrett and his team at MIT have published their results today in the journal Nature.

Hobby crafts

Barrett says the inspiration for the team’s ion plane comes partly from the movie and television series, “Star Trek,” which he watched avidly as a kid. He was particularly drawn to the futuristic shuttlecrafts that effortlessly skimmed through the air, with seemingly no moving parts and hardly any noise or exhaust.

“This made me think, in the long-term future, planes shouldn’t have propellers and turbines,” Barrett says. “They should be more like the shuttles in ‘Star Trek,’ that have just a blue glow and silently glide.”

MIT Motorless Plane 01 PRESS Web
A new MIT plane is propelled via ionic wind. Batteries in the fuselage (tan compartment in front of plane) supply voltage to electrodes (blue/white horizontal lines) strung along the length of the plane, generating a wind of ions that propels the plane forward. Image, Christine Y. He

About nine years ago, Barrett started looking for ways to design a propulsion system for planes with no moving parts. He eventually came upon “ionic wind,” also known as electroaerodynamic thrust — a physical principle that was first identified in the 1920s and describes a wind, or thrust, that can be produced when a current is passed between a thin and a thick electrode. If enough voltage is applied, the air in between the electrodes can produce enough thrust to propel a small aircraft.

For years, electroaerodynamic thrust has mostly been a hobbyist’s project, and designs have for the most part been limited to small, desktop “lifters” tethered to large voltage supplies that create just enough wind for a small craft to hover briefly in the air. It was largely assumed that it would be impossible to produce enough ionic wind to propel a larger aircraft over a sustained flight.

“It was a sleepless night in a hotel when I was jet-lagged, and I was thinking about this and started searching for ways it could be done,” he recalls. “I did some back-of-the-envelope calculations and found that, yes, it might become a viable propulsion system,” Barrett says. “And it turned out it needed many years of work to get from that to a first test flight.”

Ions take flight

The team’s final design resembles a large, lightweight glider. The aircraft, which weighs about 5 pounds and has a 5-meter wingspan, carries an array of thin wires, which are strung like horizontal fencing along and beneath the front end of the plane’s wing. The wires act as positively charged electrodes, while similarly arranged thicker wires, running along the back end of the plane’s wing, serve as negative electrodes.

The fuselage of the plane holds a stack of lithium-polymer batteries. Barrett's ion plane team included members of Professor David Perreault’s Power Electronics Research Group in the Research Laboratory of Electronics, who designed a power supply that would convert the batteries’ output to a sufficiently high voltage to propel the plane. In this way, the batteries supply electricity at 40,000 volts to positively charge the wires via a lightweight power converter.

Once the wires are energized, they act to attract and strip away negatively charged electrons from the surrounding air molecules, like a giant magnet attracting iron filings. The air molecules that are left behind are newly ionized, and are in turn attracted to the negatively charged electrodes at the back of the plane.

As the newly formed cloud of ions flows toward the negatively charged wires, each ion collides millions of times with other air molecules, creating a thrust that propels the aircraft forward.

The team, which also included Lincoln Laboratory staff Thomas Sebastian and Mark Woolston, flew the plane in multiple test flights across the gymnasium in MIT’s duPont Athletic Center — the largest indoor space they could find to perform their experiments. The team flew the plane a distance of 60 meters (the maximum distance within the gym) and found the plane produced enough ionic thrust to sustain flight the entire time. They repeated the flight 10 times, with similar performance.

“This was the simplest possible plane we could design that could prove the concept that an ion plane could fly,” Barrett says. “It’s still some way away from an aircraft that could perform a useful mission. It needs to be more efficient, fly for longer, and fly outside.”

MIT Motorless Plane 02 PRESS Web
A general blueprint for an MIT plane propelled by ionic wind. The system may be used to propel small drones and even lightweight aircraft, as an alternative to fossil fuel propulsion. Image, MIT Electric Aircraft Initiative

The new design is a “big step” toward demonstrating the feasibility of ion wind propulsion, according to Franck Plouraboue, senior researcher at the Institute of Fluid Mechanics in Toulouse, France, who notes that researchers previously weren’t able to fly anything heavier than a few grams.

“The strength of the results are a direct proof that steady flight of a drone with ionic wind is sustainable,” says Plouraboue, who was not involved in the research. “[Outside of drone applications], it is difficult to infer how much it could influence aircraft propulsion in the future. Nevertheless, this is not really a weakness but rather an opening for future progress, in a field which is now going to burst.”

Barrett’s team is working on increasing the efficiency of their design, to produce more ionic wind with less voltage. The researchers are also hoping to increase the design’s thrust density — the amount of thrust generated per unit area. Currently, flying the team’s lightweight plane requires a large area of electrodes, which essentially makes up the plane’s propulsion system. Ideally, Barrett would like to design an aircraft with no visible propulsion system or separate controls surfaces such as rudders and elevators.

“It took a long time to get here,” Barrett says. “Going from the basic principle to something that actually flies was a long journey of characterizing the physics, then coming up with the design and making it work. Now the possibilities for this kind of propulsion system are viable.”

This research was supported, in part, by MIT Lincoln Laboratory Autonomous Systems Line, the Professor Amar G. Bose Research Grant, and the Singapore-MIT Alliance for Research and Technology (SMART). The work was also funded through the Charles Stark Draper and Leonardo career development chairs at MIT.

back to newsletter Jennifer Chu | MIT News Office
November 21, 2018

 

An MIT team has devised a lithium metal anode that could improve the longevity and energy density of future batteries.
MIT Anodes Cathodes Li
New research by engineers at MIT and elsewhere could lead to batteries that can pack more power per pound and last longer. Illustration, MIT News.

New research by engineers at MIT and elsewhere could lead to batteries that can pack more power per pound and last longer, based on the long-sought goal of using pure lithium metal as one of the battery’s two electrodes, the anode.  

The new electrode concept comes from the laboratory of Ju Li, the Battelle Energy Alliance Professor of Nuclear Science and Engineering and professor of materials science and engineering. It is described Feb. 3, 2020, in the journal Nature, in a paper co-authored by Yuming Chen and Ziqiang Wang at MIT, along with 11 others at MIT and in Hong Kong, Florida, and Texas.

The design is part of a concept for developing safe all-solid-state batteries, dispensing with the liquid or polymer gel usually used as the electrolyte material between the battery’s two electrodes. An electrolyte allows lithium ions to travel back and forth during the charging and discharging cycles of the battery, and an all-solid version could be safer than liquid electrolytes, which have high volatilility and have been the source of explosions in lithium batteries.

“There has been a lot of work on solid-state batteries, with lithium metal electrodes and solid electrolytes,” Li says, but these efforts have faced a number of issues.

One of the biggest problems is that when the battery is charged up, atoms accumulate inside the lithium metal, causing it to expand. The metal then shrinks again during discharge, as the battery is used. These repeated changes in the metal’s dimensions, somewhat like the process of inhaling and exhaling, make it difficult for the solids to maintain constant contact, and tend to cause the solid electrolyte to fracture or detach.

Another problem is that none of the proposed solid electrolytes are truly chemically stable while in contact with the highly reactive lithium metal, and they tend to degrade over time.

Most attempts to overcome these problems have focused on designing solid electrolyte materials that are absolutely stable against lithium metal, which turns out to be difficult.  Instead, Li and his team adopted an unusual design that utilizes two additional classes of solids, “mixed ionic-electronic conductors” (MIEC) and “electron and Li-ion insulators” (ELI), which are absolutely chemically stable in contact with lithium metal.

The researchers developed a three-dimensional nanoarchitecture in the form of a honeycomb-like array of hexagonal MIEC tubes, partially infused with the solid lithium metal to form one electrode of the battery, but with extra space left inside each tube. When the lithium expands in the charging process, it flows into the empty space in the interior of the tubes, moving like a liquid even though it retains its solid crystalline structure. This flow, entirely confined inside the honeycomb structure, relieves the pressure from the expansion caused by charging, but without changing the electrode’s outer dimensions or the boundary between the electrode and electrolyte. The other material, the ELI, serves as a crucial mechanical binder between the MIEC walls and the solid electrolyte layer.

“We designed this structure that gives us three-dimensional electrodes, like a honeycomb,” Li says. The void spaces in each tube of the structure allow the lithium to “creep backward” into the tubes, “and that way, it doesn’t build up stress to crack the solid electrolyte.” The expanding and contracting lithium inside these tubes moves in and out, sort of like a car engine’s pistons inside their cylinders. Because these structures are built at nanoscale dimensions (the tubes are about 100 to 300 nanometers in diameter, and tens of microns in height), the result is like “an engine with 10 billion pistons, with lithium metal as the working fluid,” Li says.

Because the walls of these honeycomb-like structures are made of chemically stable MIEC, the lithium never loses electrical contact with the material, Li says. Thus, the whole solid battery can remain mechanically and chemically stable as it goes through its cycles of use. The team has proved the concept experimentally, putting a test device through 100 cycles of charging and discharging without producing any fracturing of the solids.

MIT anodes cathodes Li
Reversible lithium (Li) metal plating and stripping in a carbon tubule with an inner diameter of 100 nanometers. Courtesy of the researchers.

Li says that though many other groups are working on what they call solid batteries, most of those systems actually work better with some liquid electrolyte mixed with the solid electrolyte material. “But in our case,” he says, “it’s truly all solid. There is no liquid or gel in it of any kind.”  

The new system could lead to safe anodes that weigh only a quarter as much as their conventional counterparts in lithium-ion batteries, for the same amount of storage capacity. If combined with new concepts for lightweight versions of the other electrode, the cathode, this work could lead to substantial reductions in the overall weight of lithium-ion batteries. For example, the team hopes it could lead to cellphones that could be charged just once every three days, without making the phones any heavier or bulkier.

One new concept for a lighter cathode was described by another team led by Li, in a paper that appeared last month in the journal Nature Energy, co-authored by MIT postdoc Zhi Zhu and graduate student Daiwei Yu. The material would reduce the use of nickel and cobalt, which are expensive and toxic and used in present-day cathodes. The new cathode does not rely only on the capacity contribution from these transition-metals in battery cycling. Instead, it would rely more on the redox capacity of oxygen, which is much lighter and more abundant. But in this process the oxygen ions become more mobile, which can cause them to escape from the cathode particles. The researchers used a high-temperature surface treatment with molten salt to produce a protective surface layer on particles of manganese- and lithium-rich metal-oxide, so the amount of oxygen loss is drastically reduced.

Even though the surface layer is very thin, just 5 to 20 nanometers thick on a 400 nanometer-wide particle, it provides good protection for the underlying material. “It’s almost like immunization,” Li says, against the destructive effects of oxygen loss in batteries used at room temperature. The present versions provide at least a 50 percent improvement in the amount of energy that can be stored for a given weight, with much better cycling stability.

The team has only built small lab-scale devices so far, but “I expect this can be scaled up very quickly,” Li says. The materials needed, mostly manganese, are significantly cheaper than the nickel or cobalt used by other systems, so these cathodes could cost as little as a fifth as much as the conventional versions.

The research teams included researchers from MIT, Hong Kong Polytechnic University, the University of Central Florida, the University of Texas at Austin, and Brookhaven National Laboratories in Upton, New York. The work was supported by the National Science Foundation.

back to newsletterDavid L. Chandler | MIT News Office
February 3, 2020

 

Tuesday, 23 July 2019 15:15

New insights into bismuth’s character

Theorists at MIT and collaborators uncover hidden topological insulator states in bismuth crystals.
A crystal of bismuth has a staircase-like appearance because of the repeating honeycomb-like structure of its atoms. Researchers at MIT and colleagues have conducted a theoretical analysis to reveal several previously unidentified topological properties of bismuth.
A crystal of bismuth has a staircase-like appearance because of the repeating honeycomb-like structure of its atoms. Researchers at MIT along with colleagues in Boston, Singapore and Taiwan have conducted a theoretical analysis to reveal several previously unidentified topological properties of bismuth. One of these topological properties makes bismuth a robust electronic conductor along its edges where horizontal and vertical faces meet, which physicists call a hinge state. Image, Denis Paiste, Materials Research Laboratory.

The search for better materials for computers and other electronic devices has focused on a group of materials known as “topological insulators” that have a special property of conducting electricity on the edge of their surfaces like traffic lanes on a highway. This can increase energy efficiency and reduce heat output.

The first experimentally demonstrated topological insulator in 2009 was bismuth-antimony, but only recently did researchers identify pure bismuth as a new type of topological insulator. A group of researchers in Europe and the U.S. provided both experimental evidence and theoretical analysis in a 2018 Nature Physics report.

Now, researchers at MIT along with colleagues in Boston, Singapore and Taiwan have conducted a theoretical analysis to reveal several more previously unidentified topological properties of bismuth. The team was led by senior authors MIT Associate Professor of Physics Liang Fu, MIT Professor of Physics Nuh Gedik, Northeastern University Distinguished Professor Arun Bansil (Physics) and Research Fellow Hsin Lin at Academica Sinica (Taiwan).

“It’s kind of a hidden topology where people did not know that it can be that way,” says MIT Postdoc Su-Yang Xu, a coauthor of the paper published recently in PNAS.

Topology is a mathematical tool that physicists use to study electronic properties by analyzing electrons’ quantum wave functions. The “topological” properties give rise to a high degree of stability in the material and make its electronic structure very robust against minor imperfections in the crystal such as impurities or minor distortions of its shape such as stretching or squeezing.

“Let’s say I have a crystal that has imperfections. Those imperfections, as long as they are not so dramatic, then my electrical property will not change,” Xu explains. “If there is such topology and if the electronic properties are uniquely tied to the topology rather than the shape, then it will be very robust.”

“In this particular compound, unless you somehow apply pressure or something to distort the crystal structure, otherwise this conduction will always be protected,” Xu says.

Since the electrons carrying a certain spin can only move in one direction in these topological materials, they cannot bounce backwards or scatter, which is the behavior that makes silicon and copper based electronic devices heat up.

While materials scientists seek to identify materials with fast electrical conduction and low heat output for advanced computers, physicists want to classify the types of topological and other properties that underlie these better performing materials.

In the new paper, “Topology on a new facet of bismuth,” the authors calculated that bismuth should show a state known as a “Dirac surface state,” which is considered a hallmark of these topological insulators. They found that the crystal is unchanged by a half circle rotation (180 degrees). This is called a twofold rotational symmetry. Such a twofold rotational symmetry protects the Dirac surface states. If this twofold rotation symmetry of the crystal is disrupted, these surface states lose their topological protection.

Bismuth also features a topological state along certain edges of the crystal where two vertical and horizontal faces meet called a “hinge” state. To fully realize the desired topological effects in this material, the hinge state and other surface states must be coupled to another electronic phenomenon known as “band inversion” that the theorists’ calculations show also is present in bismuth. They predict that these topological surface states could be confirmed by using an experimental technique known as photoemission spectroscopy.

If electrons flowing through copper are like a school of fish swimming through a lake in summer, electrons flowing across a topological surface are more like ice skaters crossing the lake’s frozen surface in winter. For bismuth, however, in the hinge state, their motion would be more akin to skating on the corner edge of an ice cube.

The researchers also found that in the hinge state, as the electrons’ move forward, their momentum and another property called spin, which defines a clockwise or counterclockwise rotation of the electrons, is “locked.” “Their direction of spinning is locked with respect to their direction of motion,” Xu explains.

These additional topological states might help explain why bismuth lets electrons travel through it in much farther than most other materials and why it conducts electricity efficiently with many fewer electrons than materials such as copper.

“If we really want to make these things useful and significantly improve the performance of our transistors, we need to find good topological materials, good in terms of they are easy to make, they are not toxic, and also they are relatively abundant on earth,” Xu suggests. Bismuth, which is an element that is safe for human consumption in the form of remedies to treat heartburn, for example, meets all these requirements.

“This work is a culmination of a decade and a half’s worth of advancement in our understanding of symmetry protected topological materials,” says David Hsieh, Professor of Physics at Caltech, who was not involved in this research.

“I think that these theoretical results are robust and it is simply a matter of experimentally imaging them using techniques like angle-resolved photoemission spectroscopy, which Prof. Gedik is an expert in,” Hsieh adds.

Northeastern University Professor of Physics Gregory Fiete notes that “Bismuth-based compounds have long played a starring role in topological materials, though bismuth itself was originally believed to be topologically trivial.”

“Now, this team has discovered that pure bismuth is multiply topological with a pair of surface Dirac cones untethered to any particular momentum value,” says Fiete, who also was not involved in this research. “The possibility to move the Dirac cones through external parameter control may open the way to applications that exploit this feature."

Caltech Prof. Hsieh notes that the new findings add to the numbers of ways that topologically protected metallic states can be stabilized in materials. “If bismuth can be turned from semimetal into insulator, then isolation of these surface states in electrical transport can be realized, which may be useful for low power electronics applications,” Hsieh explains.

Also contributing to the bismuth topology paper were MIT Postdoc Qiong Ma; Tay-Rong Chang of the Department of Physics, National Cheng Kung University, Taiwan, and the Center for Quantum Frontiers of Research & Technology, Taiwan; Xiaoting Zhou, Department of Physics, National Cheng Kung University, Taiwan; and Chuang-Han Hsu, Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore.

This work was partly supported by the Center for Integrated Quantum Materials and the U.S. Department of Energy, Materials Sciences and Engineering division.

back to newsletterDenis Paiste, Materials Research Laboratory
July 29, 2019

Atmospheric chemist takes on pollutants and the global treaties written to control them.

MIT Noelle Selin A1 Press Brauer Web
MIT associate professor Noelle Selin uses atmospheric chemistry models to understand how international environmental treaties and regulations affect the transport of toxins. Photo, M. Scott Brauer

In 1995, the Governing Council of the United Nations Environment Program called for a united, global effort to reduce persistent organic pollutants (POPs) — synthetic chemicals such as PCBs, DDT, and dioxins. The compounds were known to persist and accumulate far from their sources, polluting the environment and causing adverse health effects in humans.

As work on a global treaty progressed, Noelle Eckley Selin, then a college intern at the Environmental Protection Agency, had the opportunity to play a small part in the process that eventually produced the Stockholm Convention on Persistent Organic Pollutants. She was tasked in 1997 with evaluating potential chemicals as add-ons to the “dirty dozen” that the treaty proposed to regulate.

“The treaty was designed as a dynamic instrument, so countries could add chemicals to it to respond to emerging threats,” recalls Selin, now a tenured associate professor in MIT’s Institute for Data, Systems, and Society (IDSS) and the Department of Earth, Atmospheric and Planetary Sciences (EAPS). “But the EPA wanted to know what scientific criteria to use to choose those substances. So I had to go into the dusty basement of the EPA and look up how long these random chemicals persisted in the environment.”

Selin presented her findings to EPA officials, including the agency’s assistant administrators.

“That experience gave me the sense that even as an undergrad with some scientific knowledge, I had a lot to contribute,” Selin says. “It really introduced me to toxics in the environment, which is the entire theme of my research group now, and also highlighted the connection between basic science and international politics.”

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Read more at the MIT News Office.

Jennifer Chu | MIT News Office
October 22, 2017

Friday, 08 February 2019 14:59

Observing hydrogen’s effects in metal

Microscopy technique could help researchers design safer reactor vessels or hydrogen storage tanks.
This illustration depicts the main elements of the system the team used: The multicolored slab at center is the metal layer being studied, the pale blue region at left is the electrolyte solution used as a source of hydrogen, the small blue dots are the hydrogen atoms, and the green laser beams at right are probing the process. The large cylinder at right is a probe used to indent the metal to test its mechanical properties.  Courtesy of the researchers
This illustration depicts the main elements of the system the team used: The multicolored slab at center is the metal layer being studied, the pale blue region at left is the electrolyte solution used as a source of hydrogen, the small blue dots are the hydrogen atoms, and the green laser beams at right are probing the process. The large cylinder at right is a probe used to indent the metal to test its mechanical properties. Courtesy of the researchers

Hydrogen, the second-tiniest of all atoms, can penetrate right into the crystal structure of a solid metal.

That’s good news for efforts to store hydrogen fuel safely within the metal itself, but it’s bad news for structures such as the pressure vessels in nuclear plants, where hydrogen uptake eventually makes the vessel’s metal walls more brittle, which can lead to failure. But this embrittlement process is difficult to observe because hydrogen atoms diffuse very fast, even inside the solid metal.

Now, researchers at MIT have figured out a way around that problem, creating a new technique that allows the observation of a metal surface during hydrogen penetration. Their findings are described in a paper published Feb. 4, 2019, in the International Journal of Hydrogen Energy, by MIT postdoc Jinwoo Kim and Thomas B. King Assistant Professor of Metallurgy C. Cem Tasan.

“It's definitely a cool tool,” says Chris San Marchi, a distinguished member of the technical staff at Sandia National Laboratories, who was not involved in this work. “This new imaging platform has the potential to address some interesting questions about hydrogen transport and trapping in materials, and potentially about the role of crystallography and microstructural constituents on the embrittlement process.”

Hydrogen fuel is considered a potentially major tool for limiting global climate change because it is a high-energy fuel that could eventually be used in cars and planes. However, expensive and heavy high-pressure tanks are needed to contain it. Storing the fuel in the crystal lattice of the metal itself could be cheaper, lighter, and safer — but first the process of how hydrogen enters and leaves the metal must be better understood.

“Hydrogen can diffuse at relatively high rates in the metal, because it’s so small,” Tasan says. “If you take a metal and put it in a hydrogen-rich environment, it will uptake the hydrogen, and this causes hydrogen embrittlement,” he says. That’s because the hydrogen atoms tend to segregate in certain parts of the metal crystal lattice, weakening its chemical bonds.

The new way of observing the embrittlement process as it happens may help to reveal how the embrittlement gets triggered, and it may suggest ways of slowing the process — or of avoiding it by designing alloys that are less vulnerable to embrittlement.

Sandia’s San Marchi says that “this method may play an important role — in coordination with other techniques and simulation — to illuminate the hydrogen-defect interactions that lead to hydrogen embrittlement. With more comprehensive understanding of the mechanisms of hydrogen embrittlement, materials and microstructures can be designed to improve their performance under extreme hydrogen environments.”

The key to the new monitoring process was devising a way of exposing metal surfaces to a hydrogen environment while inside the vacuum chamber of a scanning electron microscope (SEM). Because the SEM requires a vacuum for its operation, hydrogen gas cannot be charged into the metal inside the instrument, and if precharged, the gas diffuses out quickly. Instead, the researchers used a liquid electrolyte that could be contained in a well-sealed chamber, where it is exposed to the underside of a thin sheet of metal. The top of the metal is exposed to the SEM electron beam, which can then probe the structure of the metal and observe the effects of the hydrogen atoms migrating into it.

The hydrogen from the electrolyte “diffuses all the way through to the top” of the metal, where its effects can be seen, Tasan says. The basic design of this contained system could also be used in other kinds of vacuum-based instruments to detect other properties. “It’s a unique setup. As far as we know, the only one in the world that can realize something like this,” he says.

Electron microscope images show the buildup of hydrogen within the crystal structure of a titanium alloy. The images reveal the way hydrogen, depicted in blue, preferentially migrates into the interfaces between crystal grains in the metal. Courtesy of the researchers.
Electron microscope images show the buildup of hydrogen within the crystal structure of a titanium alloy. The images reveal the way hydrogen, depicted in blue, preferentially migrates into the interfaces between crystal grains in the metal. Courtesy of the researchers.

In their initial tests of three different metals — two different kinds of stainless steel and a titanium alloy — the researchers have already made some new findings. For example, they observed the formation and growth process of a nanoscale hydride phase in the most commonly used titanium alloy, at room temperature and in real time.

Devising a leakproof system was crucial to making the process work. The electrolyte needed to charge the metal with hydrogen, “is a bit dangerous for the microscope,” Tasan says. “If the sample fails and the electrolyte is released into the microscope chamber,” it could penetrate far into every nook and cranny of the device and be difficult to clean out. When the time came to carry out their first experiment in the specialized and expensive equipment, he says, “we were excited, but also really nervous. It was unlikely that failure was going to take place, but there’s always that fear.”

Kaneaki Tsuzaki, a distinguished professor of chemical engineering at Kyushu University in Japan, who was not involved in this research, says this “could be a key technique to solve how hydrogen affects dislocation motion. It is very challenging because an acid solution for hydrogen cathodic charging is circulating into an SEM chamber. It is one of the most dangerous measurements for the machine. If the circulation joints leak, a very expensive scanning electron microscope (SEM) would be broken due to the acid solution. A very careful design and a very high-skill setup are necessary for making this measurement equipment.”

Tsuzaki adds that “once it is accomplished, outputs by this method would be super. It has very high spatial resolution due to SEM; it gives in-situ observations under a well-controlled hydrogen atmosphere.” As a result, he says, he believes that Tasan and Kim “will obtain new findings of hydrogen-assisted dislocation motion by this new method, solve the mechanism of hydrogen-induced mechanical degradation, and develop new hydrogen-resistant materials.”

The work was supported by the Exelon Corp through the MIT Energy Initiative's Low-Carbon Energy Center for Advanced Nuclear Energy Systems.

back to newsletterDavid L. Chandler | MIT News Office
February 4, 2019

The experimental scanning electron microscope setup used by the researchers to study the hydrogen-loading process. Courtesy of the researchers
The experimental scanning electron microscope setup used by the researchers to study the hydrogen-loading process. Courtesy of the researchers
Tuesday, 20 November 2018 15:00

Opportunities for materials innovation abound

Faculty researchers share insights into new capabilities at annual MIT ILP Research and Development Conference.

An era of rapid evolution of structures and devices driven by new capabilities in machine learning, nanoscale experiments, and economic modeling is unfolding, MIT materials researchers revealed during annual Industrial Liaison Program (ILP) Research and Development Conference on Nov. 15, 2018.

Pointing to progress in areas as diverse as biomedical devices, computing and energy, Carl V. Thompson, Director of the Materials Research Laboratory and Stavros Salapatas Professor of Materials Science and Engineering, noted the convergence of advances in nanoscale imaging and computerized prediction of materials structure and behavior with analysis of the likelihood of success in the marketplace.

A longstanding problem with green energy sources, including solar and wind, is their power production varies widely and is often mismatched to demand. Thompson noted the work of Associate Professor of Energy Studies Jessika Trancik, who has identified the economic value of various energy storage methods based on their relative costs. These methods include compressed air, pumped water, vanadium-based flow batteries, in addition to traditional cell type batteries such as nickel-cadmium, lithium ion and sodium-sulfur combinations. These insights can guide the focus of research.

Flow battery trade-offs

Associate Professor of Chemical Engineering Fikile R. Brushett  reported his progress on redox flow batteries for grid-level electric power storage. His lab combines economic modeling with electrochemical engineering to develop better cell designs and prototypes. For the electric grid, price and lifetime are paramount, Brushett said. Redox flow batteries are rechargeable electrochemical devices where charge storage materials, such as vanadium, are dissolved in liquid electrolytes that are housed in tanks. To store and release power, the redox active electrolytes are pumped to a separate reactor where they undergo reversible oxidation and reduction reactions on the surface of porous carbon electrodes. Compared to enclosed batteries, this configuration offers several important advantages including long lifetimes and independent scaling of power and energy. “If you want more energy, you buy another tank,” he said.

The trade-off with these flow batteries is that current active materials, such as vanadium, are relatively expensive meaning that system costs are high and the energy density is relatively low meaning they are much bigger than lithium-ion batteries of comparable power. But, he noted, for grid storage energy density is not at a premium.

Brushett is studying water-based chemistries with the hope of creating significantly cheaper flow batteries. One possibility is incorporating organic chemicals such as anthraquinone into the process. “I see a lot of opportunity for scientific learning,” he said.

Appetite for electrons

Assistant Professor of Materials Science and Engineering Rafael Jaramillo is working to harness elements from the chalcogen group of the periodic table for solar and photonics devices. These elements – Oxygen, Sulfur, Selenium and Tellurium – have a large variation in their appetite for electrons.

“It means they give you the biggest space of electronic materials functionality. So chalcogenides give you dielectrics, they give you semiconductors, and they give you semi-metals,” Jaramillo said. “So for somebody who is interested in electronic device technology, this is a great playground.”

Materials based on these chalcogenides change their atomic structure in response to light, and this reversible structural change holds promise for new devices suitable for integrated photonics and photovoltaics, Jaramillo said. One particular alloy of germanium, antimony and tellurium (Ge-Sb-Te, or GST) undergoes a desirable structural change, which changes its optical property in the infrared light range, but suffers from fatigue, which produces cracks in the material.

Jaramillo is working on extremely thin metal alloys that can undergo this structural change without breaking down. This work, which is supported by the Office of Naval Research, involves computerized quantum mechanical calculations of the expected optical properties of these materials in different structural phases and then verifying the predictions experimentally.

In other realms, Jaramillo is working on chalcogenide perovskite thin films for solar cells, and is proposing a method known as tape casting to produce coatings for infrared optics.

Chip-scale chemical sensors

Juejun (JJ) Hu, Associate Professor of Materials Science and Engineering, spoke about his new design for computer chip-sized spectrometers, devices that identify chemicals based on their response to light and that are also used to monitor optical networks. Typical benchtop spectrometers are the size of a desktop computer printer.

Hu and colleagues designed a spectrometer that acquires high-resolution spectra using a digital Fourier transformation technique in a chip-sized device. The system employs electronic optical switches instead of mirrors. A library of wavelengths of light associated with individual chemicals provide highly specific identification, making spectrometers ideal for sensing in complex environments, Hu said. The proof-of-concept spectrometer operates in the standard communication wavelength range of 1550 nanometers to 1570 nanometers, which is in the infrared range. “In all cases, we were able to reproduce spectrum with very high fidelity,” Hu said. Significantly, the more of these optical switches that are added to the setup, the higher the spectral clarity becomes, and the device performance scales exponentially with the number of switches.

One possible use of these tiny chips is in sensors to detect leaks on natural gas pipelines. Hu estimates such a system could pay for itself in three years and then save $5 billion over 10 years.

Needle in a haystack

Rafael Gomez-Bombarelli, Toyota Assistant Professor in Materials Processing, uses a process called high-throughput virtual screening. He uses machine learning to blend data from first principles calculations with data from experiments for discovering and engineering new molecules and materials for applications such as organic LEDs, photodiodes, and aqueous redox flow batteries. The process, he says, is “essentially looking for the needle in the haystack in material discovery.”

“We use our theoretical predictions, throw in chemical structure and we predict experimental properties,” Gomez-Bombarelli said. These include observable properties such as color emission and color absorption or battery efficiency, but computer simulations can often predict expected properties without the need for physical experiments.

One twist to this strategy is using numbers to represent molecules in a continuous, reversible way. “This allows us to optimize complex chemicals just like we optimize numbers, and then decode the optimal solution back to a chemical structure. We were able to rediscover a lot of molecules that somebody has created already, as well as completely novel efficient compounds,” he said.

Gomez-Bombarelli is applying these tools to discover better chemical compositions for peptide-based drug delivery; organic molecules for use as electrolytes in water-based redox flow batteries; polymers for photodiodes and lithium-ion batteries; or zeolites for catalyzing chemical reactions.

Talkative fibers

Yoel Fink, CEO of Advanced Functional Fabrics of America (AFFOA), described the accelerated pace of discovery in advanced fibers and fabrics at the non-profit manufacturing institute, which is a partnership of more than 75 companies and two-dozen academic institutions, state and federal agencies and private industry. “At AFFOA, years are 90 days long,” Fink said. Each three-month research period, which focuses on a specific goal outlined in AFFOA’s roadmap, is broken up into five or six two-week long sprints.

AFFOA is developing fibers where chip and power technologies are incorporated into the fiber material itself to deliver fibers with ever increasing functionality – a “Moore’s law” for fibers. AFFOA then works with industry to create fabrics that can see, hear, sense, communicate, store and convert energy, regulate temperature, monitor health or change color. The partnership aims to create new markets for advanced fabrics where these materials provide a platform for delivering high value added services – “fabrics as a service.”

Fink described AFFOA’s advanced fabric startup program that matches entrepreneurs with technology and provides them with access to large scale prototypes and market facing companies.

As an example of an advanced fabric, the ILP and AFFOA partnered to provide a programmable backpack to every ILP R&D conference attendee. The backpack communicates content that the owner defines through the AFFOA Looks app and fabric communications system. The backpacks were designed to enhance in-person networking and sharing connections in conferences and other events.

Fink, who is a professor of materials science and electrical engineering, demonstrated a transparent fiber with semiconductor chips in it that can survive underwater, as well as a soft fabric with communications capabilities.

AFFOA is currently developing a range of products working with Teufelberger, an Austria-based global firm with rope-making operations in Fall River, Mass., to pioneer the use of rope as a communication device. For example, smart rope could inform climbers about the safety of ropes on a climb, Fink said. Smart fibers could help self-driving cars to identify bicycle riders and athletes to connect with fans, he suggested.

The two-day ILP Research and Development Conference also addressed MIT’s innovation ecosystem, nanotechnology in life sciences and the future of design, with additional speakers from MIT Lincoln Laboratories.

The Materials Research Laboratory partners with ILP and MIT.nano to engage with industry and promote interdisciplinary research.

back to newsletter– Denis Paiste, Materials Research Laboratory
November 27, 2018

Related articles:
Improving materials from the nanoscale up
Introducing the latest in textiles: Soft hardware
Fabrics are the future

MIT professor sees many “big, deep questions in biology” that benefit from study by both physicists and life scientists.
MIT Profile Gore 01 PRESS Web
Associate Professor of Physics Jeff Gore. Image, Jared Charney.

It’s a pretty good bet that among MIT’s physics faculty, Jeff Gore is the only one with test tubes of yeast growing in his lab.

Gore, a biophysicist who studies population dynamics, uses yeast and other microbes to explore the fundamental rules that govern phenomena such as population collapse. His microbial communities offer a window into principles that also influence larger-scale populations that are much more difficult to study.

“Microbes are a wonderful experimentally tractable model system to try to ask the kinds of questions we’re interested in, regarding all these phenomena that are also at play in fisheries, or in zebra populations, which are very difficult to approach experimentally,” says Gore, who recently earned tenure in MIT’s Department of Physics.

Since joining MIT’s faculty in 2010, Gore has explored the roles of “cheaters” and “cooperators” in microbial communities, as well as perturbations that can nudge a stable population toward a tipping point that leads to collapse. The rapid timescale of microbial growth allows Gore and his students to conduct an experiment in just a few days, test their predictions, revise their models based on the experimental results, and then launch new experiments.

“Going back and forth between experiment and modeling is a key part of how I like to do science, and it’s really only feasible, given the timescales, in these experimentally tractable organisms with short generation times,” he says.

A physical approach to biology

Gore, who grew up on a Christmas tree farm in Corvallis, Oregon, first visited MIT as a high school senior and immediately felt at home.

“I was staying with an older graduate from my high school at one of the fraternities across the river,” he recalls. “I played ping pong with different members of the fraternity for hours, and chatted with each of them about what they were doing, what they were excited about. It definitely felt like a place that I was going to appreciate.”

Gore began his undergraduate career as a physics major but gradually added more majors until he ended up with four concentrations, in physics, mathematics, economics, and electrical engineering.

After graduating from MIT, Gore went to the University of California at Berkeley, where he began studying electron transport in carbon nanotubes. However, his PhD advisor left Berkeley soon after that, so he switched to a biophysics lab, where he worked on building new kinds of microscopes to look at and manipulate individual biological molecules, such as DNA.

He found that he enjoyed applying tools and strategies from physics to try to discover patterns that underlie biological phenomena.

“I think many physicists, probably myself included, when we first learn biology there are a lot of things to memorize, and we tend not to be very good at memorizing things, so we decide we don’t like it,” Gore says. “But over time I realized that there are a bunch of big, deep questions in biology where the approach of a physicist is complementary to the approach taken by a molecular or cell biologist.”

He says that another appealing aspect of biophysics is that it offers the opportunity to run experiments that can be contained on a lab bench, as opposed to the huge particle colliders that are required to answer many of the fundamental questions remaining in traditional physics.

“I like experiments, and I wanted to do experiments that could be put on a bench, where you could really have the lead in your own project,” he says. “You may not be able to find out the origin of dark matter, but you have real control over your own experiment.”

Population predictions

After finishing his PhD, Gore returned to MIT as a Pappalardo Fellow in the Department of Physics, where he began studying population dynamics of microbes. Using game theory, a mathematical approach traditionally used by economists to predict individuals’ behavior in certain situations, he set out to explore cooperative behavior, which benefits other members of a species at a cost to the individual.

Working with yeast populations in which some members cooperate, by producing an excess of food, and others cheat, by gorging themselves on the food produced by others, Gore found that if an individual benefits even slightly by cooperating, it can survive even when surrounded by individuals that don’t cooperate. This helps to explain the perpetuation of cooperative behavior, which had puzzled biologists because if only the fittest individuals survive, genes for a behavior that benefits other members of the population more than the cooperating individual should die out.

As a faculty member, Gore has expanded his research to include analysis of the conditions that can lead to population collapse. In 2012, he showed that he could measure a population’s risk of collapse by monitoring how quickly it recovers from small disturbances such as food shortages or overcrowding. Later, he found that monitoring variations in population density in neighboring regions — a measure that is easier to obtain — can also be used to predict risk of collapse.

Since Gore joined MIT’s faculty, the physics department has increased its focus on the field of biophysics, hiring three more specialists in that area. That core group, along with several other biophysicists in the department, launched the Physics of Living Systems group about three years ago.

“We’re working to develop a critical mass of faculty who are taking this physics approach to understanding biology, which is different and hopefully complementary to the approach taken by other departments,” Gore says. “There really are a distinct set of approaches to biology in different departments, which is great because the different approaches give different insights.”

back to newsletter

Anne Trafton | MIT News Office
May 14, 2018

 

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