Seven with MIT ties receive awards from the American Physical Society

The American Physical Society (APS) recently honored a number of individuals with ties to MIT with prizes and awards for their contributions to physics. They include: Institute Professor Arup Chakraborty; associate professors Ronald Fernando Garcia Ruiz and Lina Necib; Yuan Cao SM ’16 PhD ’20; Alina Kononov ’14; Elliott H. Lieb ’53; Haocun Yu PhD ’20; and several former MIT postdocs.

Max Delbruck Prize in Biological Physics

Institute Professor Arup Chakraborty, a professor of chemical engineering, physics, and chemistry, received the 2023 Max Delbruck Prize in Biological Physics for his role in “initiating the field of computational immunology, aimed at applying approaches from physical sciences and engineering to unravel the mechanistic underpinnings of the adaptive immune response to pathogens, and to harness this understanding to help design vaccines and therapy.”

The Delbruck Prize is named in honor of the physicist and Nobel Laureate Max Delbruck, whose influential quantitative study of genes and their susceptibility to mutations has inspired generations of physical scientists to work on biology, starting with Erwin Schroedinger’s book “What Is Life?” The annual $10,000 Delbruck Prize recognizes and encourages outstanding achievement in biological physics research. 

A chemical engineer by training, Chakraborty’s research at the crossroad of statistical physics and molecular and cellular immunology has led to discoveries regarding the immune response to pathogens, which can be harnessed for the development of potential vaccines for HIV, influenza, and other highly mutable pathogens. Most recently, he has also been studying the role of phase separation in gene regulation. The Chakraborty Group’s theoretical and computational research is distinguished by its impact on experimental and clinical studies, and they collaborate with many experimental and clinical biologists.

Teaching at both the undergraduate and graduate levels, Chakraborty is also a co-author of the 2021 book “Viruses, Pandemics, and Immunity.” He is one of just 12 MIT Institute Professors and is also one of just 25 individuals who are members of all three branches of the U.S. National Academies — National Academy of Sciences, National Academy of Medicine, and National Academy of Engineering.

Chakraborty is a core faculty member and the founding director of MIT’s Institute for Medical Engineering and Science, and a founding member of the Ragon Institute of MGH, MIT, and Harvard. He will receive the prize at January’s APS Annual Leadership Meeting in Washington.

George E. Valley Jr. Prize  

Assistant professor of physics Lina Necib PhD ’17 has been selected to receive the George E. Valley Jr. Prize, which recognizes an outstanding scientific contribution to physics by an early-career researcher.

The astroparticle physicist was recognized for the discovery of a massive new stellar structure “that may have shaped the history of the Milky Way,” and for her development of “groundbreaking new methods” to study our galaxy's dark-matter halo and growth history.

Necib uses cosmological simulations, stellar catalogs, machine learning techniques, and a background of particle physics to build the first map of dark matter in the Milky Way. Specifically, Necib uses the European Space Agency’s Gaia spacecraft’s optical telescopes to model the kinematics of accreted stars, which are stars born outside our galaxy, the Milky Way. Some of these stars originate from merger events such as the Gaia Sausage/Gaia Enceledus. She also discovered a stellar stream that wraps around the Milky Way galaxy, called Nyx, after the Greek goddess of the night, and is using spectroscopy to identify its properties.

A native of Tunisia, Necib worked with Professor Jesse Thaler to receive her PhD in theoretical physics from MIT in 2017. She rejoined the Institute as a faculty member in 2021.

The award, which recognizes an early-career individual for an outstanding scientific contribution to physics that is deemed to have significant potential for a dramatic impact on the field, provides $10,000, a certificate citing the contribution made by the recipient, an allowance for travel to the APS Medal and Prize Ceremony and Reception in Washington, and an invited talk at an APS March or April meeting. The prize is named after the late MIT professor emeritus of physics who was also an MIT alumnus.

Stuart Jay Freedman Award in Experimental Nuclear Physics  

Assistant professor of physics Ronald Fernando Garcia Ruiz was recognized with the American Physical Society’s Stuart Jay Freedman Award in Experimental Nuclear Physics "for novel studies of exotic nuclei using precision laser spectroscopy measurements, including the first spectroscopy of short-lived radioactive molecules.” 

Garcia Ruiz develops laser spectroscopy techniques to investigate the properties of subatomic particles using atoms and molecules made up of short-lived radioactive nuclei. His experimental work provides unique information about the fundamental forces of nature, the properties of nuclear matter at the limits of existence, and the search for new physics beyond the Standard Model of particle physics. 

Very recently, his team at MIT and collaborators developed a new laser spectroscopy experiment, the Resonant ionization Spectroscopy Experiments (RiSE), located at the new Department of Energy Facility for Rare Isotope Beams (FRIB) at Michigan State University. "We anticipate the RISE experiment, combined with the unique capabilities of FRIB, is going to provide major breakthroughs in our understanding of nuclei at the extremes of stability, and the use of rare atoms and molecules in fundamental physics over the next decade," Garcia Ruiz says.

A native of Colombia, Garcia Ruiz joined MIT in 2020. His award, named after distinguished experimental nuclear physicist Stuart J. Freedman, will be presented at the 2022 Fall Meeting of the APS Division of Nuclear Physics Oct. 27-30. The award includes $4,000, a certificate, and travel allowance to give a talk at the awards ceremony.

Richard L. Greene Dissertation Award in Experimental Condensed Matter or Materials Physics

Yuan Cao SM ’16, PhD ’20, now a junior fellow at Harvard University, received the 2022 Richard L. Greene Dissertation Award in Experimental Condensed Matter or Materials Physics "for pioneering discoveries of strongly correlated physics in twisted bilayer graphene."

A graduate of the Department of Electrical Engineering and Computer Science and former Jarillo-Herrero lab postdoc and Materials Research Laboratory visiting scientist, Cao is mainly focused on the quantum transport in 2D materials, especially moiré superlattices. Cao’s past work has been honored as "Nature's 10" and Physics World’s “Physics Breakthrough of the Year," in 2018.

Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics

Alina Kononov ’14, a postdoc at Sandia National Laboratories, received the Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics “for trailblazing contributions to the computational modeling of materials physics, including large-scale simulations of irradiated materials and advances in time-dependent density functional theory."

Kononov’s research interests span electronic structure theory and its applications, including time-dependent density functional theory, quantum simulation, materials physics, and high-energy density science. A 2014 graduate of MIT in physics, her later doctoral work focused on first-principles modeling of ion-irradiated surfaces and 2D materials, enabling predictive calculations of ion-induced electron emission, uncovering new surface physics, and offering insights for ion beam materials imaging and processing techniques. At Sandia National Labs, she continues to develop and apply cutting-edge methods to model excited electron dynamics.

APS Medal for Exceptional Achievement in Research

Elliott H. Lieb ’53, an alumnus of the MIT Department of Physics and a former MIT professor who is now at Princeton University, has received the 2022 APS Medal for Exceptional Achievement in Research “for major contributions to theoretical physics through obtaining exact solutions to important physical problems, which have impacted condensed matter physics, quantum information, statistical mechanics, and atomic physics."

As an MIT professor from 1968 to 1974, he became renown for the Lieb-Robinson Bound in condensed matter, which plays a significant role on the topological phases of extensive quantum systems; the “Strong subadditivity of quantum entropy,” with Mary Beth Ruskai, which now forms part of the basis of modern quantum information theory; the first “Brascamp-Lieb inequalities” that date from this period (the final version was constructed by Elliott at Princeton in 1990); and “The proof of stability of matter” with Austrian physicist Walter Thirring — their Lieb-Thirring inequalities opened a new chapter in functional analysis.
 

Carl E. Anderson Division of Laser Science Dissertation Award

Haocun Yu PhD ’20, who earned her doctorate from the MIT Department of Physics and is now a postdoc at the University of Vienna’s Walther group, received the 2021 Carl E. Anderson Division of Laser Science Dissertation Award "for leading contributions to the Advanced LIGO detectors, achieving unprecedented sensitivity through injection of squeezed stated of light, sensitive enough to observe mirror motion driven by quantum vacuum fluctuations and quantum correlations at the human scale."

Yu began working with the MIT LIGO scientific team in 2014, with a focus on the enhancement of LIGO sensitivity using quantum techniques, as well as the demonstration of macroscopic quantum phenomena in Advanced LIGO detectors. Her contributions on quantum techniques have taken macroscopic quantum mechanics to the human scale, and Advanced LIGO detectors to unprecedented sensitivity. Her recent research interest lies in the interface of quantum mechanics and gravity.   

Other researchers with MIT ties who were honored with APS awards and prizes include: Bernhard Mistlberger, former 2018-20 Pappalardo Fellow, who won the Henry Primakoff Award for Early-Career Particle Physics; Prineha Narang, former MIT physics research scholar, who won the 2023 Maria Goeppert Mayer Award; Itamar Procaccia, former MIT postdoc, who won the 2023 Leo P. Kadanoff Prize; Michael J. Ramsey-Musolf, former MIT postdoc, who won the 2023 Herman Feshbach Prize in Theoretical Nuclear Physics; B. Lee Roberts, former MIT Laboratory for Nuclear Science postdoc, who won the 2023 W.K.H. Panofsky Prize in Experimental Particle Physics; and Vivek Sharma, former mechanical engineering postdoc, who won the 2023 John H. Dillon Medal.

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Building with nanoparticles, from the bottom up

Researchers at MIT have developed a technique for precisely controlling the arrangement and placement of nanoparticles on a material, like the silicon used for computer chips, in a way that does not damage or contaminate the surface of the material.

The technique, which combines chemistry and directed assembly processes with conventional fabrication techniques, enables the efficient formation of high-resolution, nanoscale features integrated with nanoparticles for devices like sensors, lasers, and LEDs, which could boost their performance.

Transistors and other nanoscale devices are typically fabricated from the top down — materials are etched away to reach the desired arrangement of nanostructures. But creating the smallest nanostructures, which can enable the highest performance and new functionalities, requires expensive equipment and remains difficult to do at scale and with the desired resolution.

A more precise way to assemble nanoscale devices is from the bottom up. In one scheme, engineers have used chemistry to “grow” nanoparticles in solution, drop that solution onto a template, arrange the nanoparticles, and then transfer them to a surface. However, this technique also involves steep challenges. First, thousands of nanoparticles must be arranged on the template efficiently. And transferring them to a surface typically requires a chemical glue, large pressure, or high temperatures, which could damage the surfaces and the resulting device.  

The MIT researchers developed a new approach to overcome these limitations. They used the powerful forces that exist at the nanoscale to efficiently arrange particles in a desired pattern and then transfer them to a surface without any chemicals or high pressures, and at lower temperatures. Because the surface material remains pristine, these nanoscale structures can be incorporated into components for electronic and optical devices, where even minuscule imperfections can hamper performance.

“This approach allows you, through engineering of forces, to place the nanoparticles, despite their very small size, in deterministic arrangements with single-particle resolution and on diverse surfaces, to create libraries of nanoscale building blocks that can have very unique properties, whether it is their light-matter interactions, electronic properties, mechanical performance, etc.,” says Farnaz Niroui, the EE Landsman Career Development Assistant Professor of Electrical Engineering and Computer Science (EECS) at MIT, a member of the MIT Research Laboratory of Electronics, and senior author on a new paper describing the work. “By integrating these building blocks with other nanostructures and materials we can then achieve devices with unique functionalities that would not be readily feasible to make if we were to use the conventional top-down fabrication strategies alone.”

The research is published today in Science Advances. Niroui’s co-authors are lead author Weikun “Spencer” Zhu, a graduate student in the Department of Chemical Engineering, as well as EECS graduate students Peter F. Satterthwaite, Patricia Jastrzebska-Perfect, and Roberto Brenes.

Use the forces

To begin their fabrication method, known as nanoparticle contact printing, the researchers use chemistry to create nanoparticles with a defined size and shape in a solution. To the naked eye, this looks like a vial of colored liquid, but zooming in with an electron microscope would reveal millions of cubes, each just 50 nanometers in size. (A human hair is about 80,000 nanometers wide.)

The researchers then make a template in the form of a flexible surface covered with nanoparticle-sized guides, or traps, that are arranged in the shape they want the nanoparticles to take. After adding a drop of nanoparticle solution to the template, they use two nanoscale forces to move the particles into the right position. The nanoparticles are then transferred onto arbitrary surfaces.

At the nanoscale, different forces become dominant (just like gravity is a dominant force at the macroscale). Capillary forces are dominant when the nanoparticles are in liquid and van der Waals forces are dominant at the interface between the nanoparticles and the solid surface they are in contact with. When the researchers add a drop of liquid and drag it across the template, capillary forces move the nanoparticles into the desired trap, placing them precisely in the right spot. Once the liquid dries, van der Waals forces hold those nanoparticles in position.

“These forces are ubiquitous and can often be detrimental when it comes to the fabrication of nanoscale objects as they can cause the collapse of the structures. But we are able to come up with ways to control these forces very precisely to use them to control how things are manipulated at the nanoscale,” says Zhu.

They design the template guides to be the right size and shape, and in the precisely proper arrangement so the forces work together to arrange the particles. The nanoparticles are then printed onto surfaces without a need for any solvents, surface treatments, or high temperatures. This keeps the surfaces pristine and properties intact while allowing yields of more than 95 percent. To promote this transfer, the surface forces need to be engineered so that the van der Waals forces are strong enough to consistently promote particles to release from the template and attach to the receiving surface when placed in contact.

Unique shapes, diverse materials, scalable processing

The team used this technique to arrange nanoparticles into arbitrary shapes, such as letters of the alphabet, and then transferred them to silicon with very high position accuracy. The method also works with nanoparticles that have other shapes, such as spheres, and with diverse material types. And it can transfer nanoparticles effectively onto different surfaces, like gold or even flexible substrates for next-generation electrical and optical structures and devices.

Their approach is also scalable, so it can be extended to be used toward fabrication of real-world devices.

Niroui and her colleagues are now working to leverage this approach to create even more complex structures and integrate it with other nanoscale materials to develop new types of electronic and optical devices.

This work was supported, in part, by the National Science Foundation (NSF) and the NSF Graduate Research Fellowship Program.

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A faster experiment to find and study topological materials

Topological materials, an exotic class of materials whose surfaces exhibit different electrical or functional properties than their interiors, have been a hot area of research since their experimental realization in 2007 — a finding that sparked further research and precipitated a Nobel Prize in Physics in 2016. These materials are thought to have great potential in a variety of fields, and might someday be used in ultraefficient electronic or optical devices, or key components of quantum computers.

But there are many thousands of compounds that may theoretically have topological characteristics, and synthesizing and testing even one such material to determine its topological properties can take months of experiments and analysis. Now a team of researchers at MIT and elsewhere have come up with a new approach that can rapidly screen candidate materials and determine with more than 90 percent accuracy whether they are topological.

Using this new method, the researchers have produced a list candidate materials. A few of these were already known to have topological properties, but the rest are newly predicted by this approach.

The findings are reported in the journal Advanced Materials in a paper by Mingda Li, the Class ’47 Career Development Professor at MIT, graduate students (and twin sisters) Nina Andrejevic at MIT and Jovana Andrejevic at Harvard University, and seven others at MIT, Harvard, Princeton University, and Argonne National Laboratory.

Topological materials are named after a branch of mathematics that describes shapes based on their invariant characteristics, which persist no matter how much an object is continuously stretched or squeezed out of its original shape. Topological materials, similarly, have properties that remain constant despite changes in their conditions, such as external perturbations or impurities.

There are several varieties of topological materials, including semiconductors, conductors, and semimetals, among others. Initially, it was thought that there were only a handful of such materials, but recent theory and calculations have predicted that in fact thousands of different compounds may have at least some topological characteristics. The hard part is figuring out experimentally which compounds may be topological.

Applications for such materials span a wide range, including devices that could perform computational and data storage functions similarly to silicon-based devices but with far less energy loss, or devices to harvest electricity efficiently from waste heat, for example in thermal power plants or in electronic devices. Topological materials can also have superconducting properties, which could potentially be used to build the quantum bits for topological quantum computers.

But all of this relies on developing or discovering the right materials. “To study a topological material, you first have to confirm whether the material is topological or not,” Li says, “and that part is a hard problem to solve in the traditional way.” A method called density functional theory is used to perform initial calculations, which then need to be followed with complex experiments that require cleaving a piece of the material to atomic-level flatness and probing it with instruments under high-vacuum conditions. “Most materials cannot even be measured due to various technical difficulties,” Nina Andrejevic says. But for those that can, the process can take a long time. “It’s a really painstaking procedure,” she says.

Whereas the traditional approach relies on measuring the material’s photoemissions or tunneling electrons, Li explains, the new technique he and his team developed relies on absorption, specifically, the way the material absorbs X-rays. Unlike the expensive apparatus needed for the conventional tests, X-ray absorption spectrometers are readily available and can operate at room temperature and atmospheric pressure, with no vacuum needed. Such measurements are widely conducted in biology, chemistry, battery research, and many other applications, but they had not previously been applied to identifying topological quantum materials.

X-ray absorption spectroscopy provides characteristic spectral data from a given sample of material. The next challenge is to interpret that data and how it relates to the topological properties. For that, the team turned to a machine-learning model, feeding in a collection of data on the X-ray absorption spectra of known topological and nontopological materials, and training the model to find the patterns that relate the two. And it did indeed find such correlations.

“Surprisingly, this approach was over 90 percent accurate when tested on more than 1500 known materials,” Nina Andrejevic says, adding that the predictions take only seconds. “This is an exciting result given the complexity of the conventional process.”

Though the model works, as with many results from machine learning, researchers don’t yet know exactly why it works or what the underlying mechanism is that links the X-ray absorption to the topological properties. “While the learned function relating X-ray spectra to topology is complex, the result may suggest that certain attributes the measurement is sensitive to, such as local atomic structures, are key topological indicators,” Jovana Andrejevic says.

The team has used the model to construct a periodic table that displays the model’s overall accuracy on compounds made from each of the elements. It serves as a tool to help researchers home in on families of compounds that may offer the right characteristics for a given application. The researchers have also produced a preliminary study of compounds that they have used this X-ray method on, without advance knowledge of their topological status, and compiled a list of 100 promising candidate materials — a few of which were already known to be topological.

“This work represents one of the first uses of machine learning to understand what experiments are trying to tell us about complex materials,” says Joel Moore, the Chern-Simons Professor of Physics at the University of California at Berkeley, who was not associated with this research. “Many kinds of topological materials are well-understood theoretically in principle, but finding material candidates and verifying that they have the right topology of their bands can be a challenge. Machine learning seems to offer a new way to address this challenge: Even experimental data whose meaning is not immediately obvious to a human can be analyzed by the algorithm, and I am excited to see what new materials will result from this way of looking.”

Anatoly Frenkel, a professor in the Department of Materials Science and Chemical Engineering at Stony Brook University and a senior chemist at Brookhaven National Laboratory, further commented that “It was a really nice idea to consider that the X-ray absorption spectrum may hold a key to the topological character in the measured sample.”

The research team included Andrei Bernevig and Nicolas Regnault at Princeton University, Fei Han and Thanh Nguyen and Nathan Drucker at MIT, Chris Rycroft at Harvard University, and Gilberto Fabbris at Argonne National Laboratory. The work was supported by the U.S. Department of Energy and National Science Foundation.

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A “door” into the mitochondrial membrane

Mitochondria — the organelles responsible for energy production in human cells — were once free-living organisms that found their way into early eukaryotic cells over a billion years ago. Since then, they have merged seamlessly with their hosts in a classic example of symbiotic evolution, and now rely on many proteins made in their host cell’s nucleus to function properly.

Proteins on the outer membrane of mitochondria are especially important; they allow the mitochondria to communicate with the rest of the cell, and play a role in immune functions and a type of programmed cell death called apoptosis. Over the course of evolution, cells evolved a specific mechanism by which to insert these proteins — which are made in the cell’s cytoplasm — into the mitochondrial membrane. But what that mechanism was, and what cellular players were involved, has long been a mystery. 

A new paper from the labs of MIT Professor Jonathan Weissman and Caltech Professor Rebecca Voorhees provides a solution to that mystery. The work, published Oct. 21 in the journal Science, reveals that a protein called mitochondrial carrier homolog 2, or MTCH2 for short, which has been linked to many cellular processes and even diseases such as cancer and Alzheimer’s, is responsible for acting as a “door” for a variety of proteins to access the mitochondrial membrane. 

“Until now, no one knew what MTCH2 was really doing — they just knew that when you lose it, all these different things happen to the cell,” says Weissman, who is also member of the Whitehead Institute for Biomedical Research and an investigator of the Howard Hughes Medical Institute. “It was sort of a mystery why this one protein affects so many different processes. This study gives a molecular basis for understanding why MTCH2 was implicated in Alzheimer's and lipid biosynthesis and mitochondrial fission and fusion: because it was responsible for inserting all these different types of proteins in the membrane.”

“The collaboration between our labs was essential in understanding the biochemistry of this interaction, and has led to a really exciting new understanding of a fundamental question in cell biology,” Voorhees says. 

The search for a door 

In order to find out how proteins from the cytoplasm — specifically a class called tail-anchored proteins — were being inserted into the outer membranes of mitochondria, Weismann Lab postdoc and first author of the study Alina Guna, alongside Voorhees Lab graduate student Taylor Stevens and postdoc Alison Inglis, decided to use a technique called used the CRISPR interference (or CRISPRi) screening approach, which was invented by Weissman and collaborators.

“The CRISPR screen let us systematically get rid of every gene, and then look and see what happened [to one specific tail-anchored protein],” says Guna. “We found one gene, MTCH2, where when we got rid of it there was a huge decrease in how much of our protein got to the mitochondrial membrane. So we thought, maybe this is the doorway to get in.”

To confirm that MTCH2 was acting as a doorway into the mitochondrial membrane, the researchers performed additional experiments to observe what happened when MTCH2 was not present in the cell. They found that MTCH2 was both necessary and sufficient to allow tail-anchored membrane proteins to move from the cytoplasm into the mitochondrial membrane. 

MTCH2’s ability to shuttle proteins from the cytoplasm into the mitochondrial membrane is likely due to its specialized shape. The researchers ran the protein’s sequence through Alpha Fold, an artificial intelligence system that predicts a protein’s structure through its amino acid sequence, which revealed that it is a hydrophobic protein — perfect for inserting into the oily membrane — but with a single hydrophilic groove where other proteins could enter.

“It's basically like a funnel,” Guna says. “Proteins come from the cytosol, they slip into that hydrophilic groove and then move from the protein into the membrane.”

To confirm that this groove was important in the protein’s function, Guna and her colleagues designed another experiment. “We wanted to play around with the structure to see if we could change its behavior, and we were able to do that,” Guna says. “We went in and made a single point mutation, and that point mutation was enough to really change how the protein behaved and how it interacted with substrates. And then we went on and found mutations that made it less active and mutations that made it super active.”

The new study has applications beyond answering a fundamental question of mitochondria research. “There's a whole lot of things that come out of this,” Guna says. 

For one thing, MTCH2 inserts proteins key to a type of programmed cell death called apoptosis, which researchers could potentially harness for cancer treatments. “We can make leukemia cells more sensitive to a cancer treatment by giving them a mutation that changes the activity of MTCH2,” Guna says. “The mutation makes MTCH2 act more ‘greedy’ and insert more things into the membrane, and some of those things that have inserts are like pro-apoptotic factors, so then those cells are more likely to die, which is fantastic in the context of a cancer treatment.”

The work also raises questions about how MTCH2 developed its function over time. MTCH2 evolved from a family of proteins called the solute carriers, which shuttle a variety of substances across cellular membranes. “We're really interested in this evolution question of, how do you evolve a new function from an old, ubiquitous class of proteins?” Weissman says.

And researchers still have much to learn about how mitochondria interact with the rest of the cell, including how they react to stress and changes within the cell, and how proteins find their way to mitochondria in the first place. “I think that [this paper] is just the first step,” Weissman says. “This only applies to one class of membrane proteins — and it doesn't tell you all of the steps that happen after the proteins are made in the cytoplasm. For example, how are they ferried to mitochondria? So stay tuned — I think we'll be learning that we now have a very nice system for opening up this fundamental piece of cell biology.”

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Designing the cities of tomorrow

Reflecting on the mission and approach of SENSEable City Lab at MIT and his role as its director, Carlo Ratti quotes the Nobel laureate Herbert Simon, who said, “The engineer, and more generally the designer, is concerned with how things ought to be — how they ought to be in order to attain goals, and to function.” Simon was a political scientist and economist, but his groundbreaking research on decision-making within organizations was informed by disparate disciplines including computer science and cognitive science.  

Ratti, too, recognizes that, given the scope of his work, relying on the methodologies of a single field would be limiting. Our urban spaces are multifaceted constructions, a complex web of evolving systems, and collaboration between disciplines is essential to make sense of them. “The city is a universe,” says Ratti, a professor of the practice in the MIT Department of Urban Studies and Planning. “It can be viewed through the lens of economics or sociology or architecture and design. But a lab focused on cities truly requires an omni-disciplinary approach.”  

Which is why SENSEable City Lab fills its ranks with researchers with diverse specialties. It thrives, in no small part, due to collaborative effort, uniting urban planners and designers with engineers and physicists, systems mathematicians with economists and sociologists. Together they find a common language to engage with each other, industry partners, metropolitan governments, individual citizens, and disadvantaged communities to shape the future. 

In 2011, for example, the sharing economy was in full bloom, but offerings like Uber pool (UberXshare), Lyftline (Lyft Shared), and Ola did not yet exist. Nobody had quantified the viability of shared trips for passengers heading in the same direction until Ratti and SENSEable City introduced a novel concept they called “shareability networks” via the HubCab Project. Among other things, this led to the first collaboration between the Institute and Uber. Analyzing the movements of all 13,500 medallion taxis in New York City, they assembled a dataset containing the GPS coordinates of the pickup and drop-off points and corresponding times of over 170 million taxi trips. Subsequently, this dataset helped them develop a new tool that allowed for efficient modeling and optimization of trip-sharing opportunities. Their analysis showed that taxi sharing could reduce the number of trips taken by 40 percent, thereby reducing congestion, energy consumption, and pollution. 

More recently, on the social sustainability front, Ratti and his lab put big data to work on a project they call Proximate. To understand connectivity and how remote work affects innovation, they analyzed the email exchange network at MIT before and after the Institute-wide lockdown due to Covid-19. The endeavor draws on the work of sociologist and Stanford University professor Mark Granovetter, who is perhaps best known for his theory that “weak ties” — looser relationships outside of our core network of friends, family, and colleagues — are crucial bridges between social groups that encourage societal diversity, innovation, and creativity. Ratti’s examination of communications among 2,834 MIT faculty and postdocs showed a clear disintegration of “weak ties” when interactions became purely digital in nature. In other words, digital networks, for all their benefits, cannot replace in-person interactions — not if we hope to continue innovating. “The physical space accommodates and encourages the unexpected, the serendipitous, in a manner that doesn't happen, or hasn’t happened yet, in a virtual setting,” Ratti explains. 

And, in an effort to expand the impact of his lab at MIT, Ratti has established a series of satellite labs around the globe. The SENSEable Amsterdam Lab (SAL) is involved in an ongoing collaboration with the Amsterdam Institute for Advanced Metropolitan Solutions to help the Dutch capital become carbon neutral by 2050. The first SAL project is a multifunctional autonomous mobility solution befitting a city with more than 60 miles of canals. The Roboat platform has the power to transform urban waterways: it can be used to transport people, deliver goods, or for services like waste collection. It could even be used to create on-demand infrastructure, such as a floating bridge or a concert stage. 

Meanwhile, in Sweden, through a partnership with KTH Royal Institute of Technology, Ratti and his colleagues are leveraging big data to examine integration and segregation in Stockholm. Their findings: these days people tend to self-segregate by socioeconomic strata whether moving through the city or connecting online, creating what Ratti calls “liminal ghettos.” “These are not the ghettos of the past, but they are insidious, invisible fault lines,” he explains. “Once we understand those fault lines, we can take actions to bridge them so that cities fulfill their primordial function, ensuring that together we are more than each of us individually.” 

To effectively run a lab focused on cities requires stepping out of the lab and physically inhabiting urban spaces, says Ratti. But he’s also looking beyond earthbound innovations. In a truly cross-disciplinary effort that demonstrates diversity of thought and creativity, he has begun exploring the feasibility of fabricating and deploying a raft of silicon bubbles roughly the size of Brazil into outer space. The goal: reverse global warming by deflecting solar radiation before it hits our planet. The Space Bubbles project is intended as an emergency intervention should current efforts to reduce emissions fail. Joining him is a team of experts from MIT including Charles Primmerman (MIT Lincoln Laboratory), Professor Daniela Rus (MIT Computer Science and Artificial Intelligence Laboratory), Professor Gareth McKinley (MIT Department of Mechanical Engineering), and Professor Markus Buehler (MIT departments of Mechanical Engineering and Civil and Environmental Engineering). 

Emerging technologies like artificial intelligence, combined with the rise of big data, have transformed nearly every aspect of our daily lives and how we interact with each other and our built environment; consider the maturation of the internet of things and its profound effect on urban spaces. In the hands of Carlo Ratti and his SENSEable City Lab at MIT, technological advancements become tools to understand our cities and ourselves, gain new insights, and explore opportunities to redesign the future. “The convergence between the digital and physical world is radically changing the way we can understand and design cities, and ultimately how we can live in urban spaces in a different, better way,” says Ratti.

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Magnetic sensors track muscle length

Using a simple set of magnets, MIT researchers have come up with a sophisticated way to monitor muscle movements, which they hope will make it easier for people with amputations to control their prosthetic limbs.

In a new pair of papers, the researchers demonstrated the accuracy and safety of their magnet-based system, which can track the length of muscles during movement. The studies, performed in animals, offer hope that this strategy could be used to help people with prosthetic devices control them in a way that more closely mimics natural limb movement.

“These recent results demonstrate that this tool can be used outside the lab to track muscle movement during natural activity, and they also suggest that the magnetic implants are stable and biocompatible and that they don’t cause discomfort,” says Cameron Taylor, an MIT research scientist and co-lead author of both papers.

In one of the studies, the researchers showed that they could accurately measure the lengths of turkeys’ calf muscles as the birds ran, jumped, and performed other natural movements. In the other study, they showed that the small magnetic beads used for the measurements do not cause inflammation or other adverse effects when implanted in muscle.

“I am very excited for the clinical potential of this new technology to improve the control and efficacy of bionic limbs for persons with limb-loss,” says Hugh Herr, a professor of media arts and sciences, co-director of the K. Lisa Yang Center for Bionics at MIT, and an associate member of MIT’s McGovern Institute for Brain Research.

Herr is a senior author of both papers, which appear today in the journal Frontiers in Bioengineering and Biotechnology. Thomas Roberts, a professor of ecology, evolution, and organismal biology at Brown University, is a senior author of the measurement study.

Tracking movement

Currently, powered prosthetic limbs are usually controlled using an approach known as surface electromyography (EMG). Electrodes attached to the surface of the skin or surgically implanted in the residual muscle of the amputated limb measure electrical signals from a person’s muscles, which are fed into the prosthesis to help it move the way the person wearing the limb intends.

However, that approach does not take into account any information about the muscle length or velocity, which could help to make the prosthetic movements more accurate.

Several years ago, the MIT team began working on a novel way to perform those kinds of muscle measurements, using an approach that they call magnetomicrometry. This strategy takes advantage of the permanent magnetic fields surrounding small beads implanted in a muscle. Using a credit-card-sized, compass-like sensor attached to the outside of the body, their system can track the distances between the two magnets. When a muscle contracts, the magnets move closer together, and when it flexes, they move further apart.

In a study published last year, the researchers showed that this system could be used to accurately measure small ankle movements when the beads were implanted in the calf muscles of turkeys. In one of the new studies, the researchers set out to see if the system could make accurate measurements during more natural movements in a nonlaboratory setting.

To do that, they created an obstacle course of ramps for the turkeys to climb and boxes for them to jump on and off of. The researchers used their magnetic sensor to track muscle movements during these activities, and found that the system could calculate muscle lengths in less than a millisecond.

They also compared their data to measurements taken using a more traditional approach known as fluoromicrometry, a type of X-ray technology that requires much larger equipment than magnetomicrometry. The magnetomicrometry measurements varied from those generated by fluoromicrometry by less than a millimeter, on average.

“We’re able to provide the muscle-length tracking functionality of the room-sized X-ray equipment using a much smaller, portable package, and we’re able to collect the data continuously instead of being limited to the 10-second bursts that fluoromicrometry is limited to,” Taylor says.

Seong Ho Yeon, an MIT graduate student, is also a co-lead author of the measurement study. Other authors include MIT Research Support Associate Ellen Clarrissimeaux and former Brown University postdoc Mary Kate O’Donnell.

Biocompatibility

In the second paper, the researchers focused on the biocompatibility of the implants. They found that the magnets did not generate tissue scarring, inflammation, or other harmful effects. They also showed that the implanted magnets did not alter the turkeys’ gaits, suggesting they did not produce discomfort. William Clark, a postdoc at Brown, is the co-lead author of the biocompatibility study.

The researchers also showed that the implants remained stable for eight months, the length of the study, and did not migrate toward each other, as long as they were implanted at least 3 centimeters apart. The researchers envision that the beads, which consist of a magnetic core coated with gold and a polymer called Parylene, could remain in tissue indefinitely once implanted.

“Magnets don’t require an external power source, and after implanting them into the muscle, they can maintain the full strength of their magnetic field throughout the lifetime of the patient,” Taylor says.

The researchers are now planning to seek FDA approval to test the system in people with prosthetic limbs. They hope to use the sensor to control prostheses similar to the way surface EMG is used now: Measurements regarding the length of muscles will be fed into the control system of a prosthesis to help guide it to the position that the wearer intends.

“The place where this technology fills a need is in communicating those muscle lengths and velocities to a wearable robot, so that the robot can perform in a way that works in tandem with the human,” Taylor says. “We hope that magnetomicrometry will enable a person to control a wearable robot with the same comfort level and the same ease as someone would control their own limb.”

In addition to prosthetic limbs, those wearable robots could include robotic exoskeletons, which are worn outside the body to help people move their legs or arms more easily.

The research was funded by the Salah Foundation, the K. Lisa Yang Center for Bionics at MIT, the MIT Media Lab Consortia, the National Institutes of Health, and the National Science Foundation.

de MIT News https://ift.tt/gBl4Q7G

The tenured engineers of 2022

The School of Engineering has announced that MIT has granted tenure to 14 members of its faculty in the departments of Biological Engineering, Civil and Environmental Engineering, Electrical Engineering and Computer Science (which reports jointly to the School of Engineering and MIT Schwarzman College of Computing), Materials Science and Engineering, and Mechanical Engineering.

“I am truly amazed by our newest cohort of tenured faculty,” says Anantha Chandrakasan, dean of the School of Engineering and the Vannevar Bush Professor of Electrical Engineering and Computer Science. “They are a diverse group of educators and scholars whose research and commitment to teaching has had a tremendous impact on our community, in the classroom, as well as in the lab.”

This year’s newly tenured associate professors are:

Guy Bresler, an associate professor of electrical engineering and computer science, conducts research at the interface of information theory, statistics, theoretical computer science, and probability. His work aims to understand the fundamental interplay between information properties, computational complexity, and combinatorial structure in modern statistical inference problems.

Otto Cordero, an associate professor of civil and environmental engineering, studies the ecology and evolution of natural microbial collectives. His lab is interested in understanding how social and ecological interactions at microscales impact the global productivity, stability, and evolutionary dynamics of microbial ecosystems.

Michael Carbin, an associate professor of electrical engineering and computer science, investigates the design, semantics, and implementation of language-driven systems. His focus is on systems that operate in the presence of uncertainty in their environment, implementation, or execution.

Ming Guo, an associate professor of mechanical engineering, works at the interface of mechanics, physics, and cell biology, seeking to understand how physical properties and biological function affect each other in cellular and multicellular systems, and how physical and material laws govern the behavior of living cells and their abilities to deform, move, remodel, and function.

Stefanie Jegelka, an associate professor of electrical engineering and computer science, focuses her research on algorithmic machine learning, which spans modeling, optimization algorithms, theory, and applications. In particular, she has been working on exploiting mathematical structure for discrete and combinatorial machine-learning problems, robustness, and the scaling of machine-learning algorithms.

Jeehwan Kim, an associate professor of mechanical engineering and of materials science and engineering, researches topics ranging from basic material physics/mechanics to electronic/photonic devices and systems for next generation electronics. His group focuses on innovation in nanotechnology for next generation computing and electronics

Angela Koehler, an associate professor of biological engineering, focuses on building chemical tools and methods for studying temporal aspects of transcriptional regulation in development and disease with a focus on cancer. Her lab pursues these goals by discovering and developing direct small-molecule probes of proteins involved in transcriptional regulation such as transcription factors and chromatin modifying enzymes.

Mathias Kolle, an associate professor of mechanical engineering, leverages insights into biological light manipulation strategies to design and realize multifunctional bioinspired optical materials for 21st century technology applications, using cost-efficient, scalable microfabrication, self-assembly based techniques, and biomimetic morphogenesis processes.

Tim Kraska, an associate professor of electrical engineering and computer science, is co-director of the Data System and AI LAB in MIT’s Computer Science and Artificial Intelligence Laboratory (CSAIL), co-founder of Instancio (acquired), and co-founder of Einblick Analytics (einblick.ai). Currently, his research focuses on building systems for machine learning, increasing the efficiency of data-intensive systems, and democratizing data science through machine learning.

James LeBeau, an associate professor of materials science and engineering, focuses on applying and developing revolutionary (scanning) transmission electron microscopy techniques to connect the atomic structure and chemistry of defects/interfaces with material properties for quantum computing, energy storage, power electronics, dielectrics, and optical applications.

Luqiao Liu, an associate professor of electrical engineering and computer science, focuses on fabricating nanoscale spintronic devices to achieve efficient control over magnetic dynamics. He also explores new material and physics mechanisms to improve the performance of spintronic devices for memory, logic, and neuromorphic applications.

Robert Macfarlane, an associate professor of materials science and engineering, is focused on developing a set of design principles for synthesizing new inorganic/organic composite materials, where nanoscale structure can be manipulated to tune the emergent physical properties of a bulk material.

Desirée Plata, an associate professor of in civil and environmental engineering, focuses her research on novel material and industrial process design; carbon-based transformations; global carbon management and response strategies; resource management utilization and efficiency; and environmental sustainability.

C. Cem Tasan, the Thomas B. King Professor of Metallurgy and associate professor of materials science and engineering, explores the boundaries of physical metallurgy, solid mechanics, and in-situ microscopy to design new alloys with exceptional damage-resistance.

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