Two from MIT named 2025 Gates Cambridge Scholars

MIT senior Markey Freudenburg-Puricelli and recent alumna Abigail (“Abbie”) Schipper ’24 have been selected as Gates Cambridge Scholars and will begin graduate studies this fall in the field of their choice at Cambridge University in the U.K.

Now celebrating its 25th year, the Gates Cambridge program provides fully funded post-graduate scholarships to outstanding applicants from countries outside of the U.K. The mission of Gates Cambridge is to build a global network of future leaders committed to changing the world for the better.

Students interested in applying to Gates Cambridge should contact Kim Benard, associate dean of distinguished fellowships in Career Advising and Professional Development.

Markey Freudenburg-Puricelli

Freudenburg-Puricelli is majoring in Earth, atmospheric, and planetary sciences and minoring in Spanish. Her passion for geoscience has led her to travel to different corners of the world to conduct geologic fieldwork. These experiences have motivated her to pursue a career in developing scientific policy and environmental regulation that can protect those most vulnerable to climate change. As a Gates Cambridge Scholar, she will pursue an MPhil in environmental policy.

Arriving at MIT, Freudenburg-Puricelli joined the Terrascope first-year learning community, which focuses on hands-on education relating to global environmental issues. She then became an undergraduate research assistant in the McGee Lab for Paleoclimate and Geochronology, where she gathered and interpreted data used to understand climate features of permafrost across northern Canada.

Following a summer internship in Chile researching volcanoes at the Universidad Católica del Norte, Freudenburg-Puricelli joined the Gehring Lab for Plant Genetics, Epigenetics, and Seed Biology. Last summer, she traveled to Peru to work with the Department of Paleontology at the Universidad Nacional de Piura, conducting fieldwork and preserving and organizing fossil specimens. Freudenburg-Puricelli has also done fieldwork on sedimentology in New Mexico, geological mapping in the Mojave Desert, and field oceanography onboard the SSV Corwith Cramer.

On campus, Freudenburg-Puricelli is an avid glassblower and has been a teaching assistant at the MIT glassblowing lab. She is also a tour guide for the MIT Office of Admissions and has volunteered with the Department of Earth, Atmospheric and Planetary Sciences’ first-year pre-orientation program.

Abigail “Abbie” Schipper ’24

Originally from Portland, Oregon, Schipper graduated from MIT with a BS in mechanical engineering and a minor in biology. At Cambridge, she will pursue an MPhil in engineering, researching medical devices used in pre-hospital trauma systems in low- and middle-income countries with the Cambridge Health Systems Design group.

At MIT, Schipper was a member of MIT Emergency Medical Services, volunteering on the ambulance and serving as the heartsafe officer and director of ambulance operations. Inspired by her work in CPR education, she helped create the LifeSaveHer project, which aims to decrease the gender disparity in out-of-hospital cardiac arrest survival outcomes through the creation of female CPR mannequins and associated research. This team was the first-place winner of the 2023 PKG IDEAS Competition and a recipient of the Eloranta Research Fellowship.

Schipper’s work has also focused on designing medical devices for low-resource or extreme environments. As an undergraduate, she performed research in the lab of Professor Giovanni Traverso, where she worked on a project designing a drug delivery implant for regions with limited access to surgery. During a summer internship at the University College London Collaborative Center for Inclusion Health, she worked with the U.K.’s National Health Service to create durable, low-cost carbon dioxide sensors to approximate the risk of airborne infectious disease transmission in shelters for people experiencing homelessness.

After graduation, Schipper interned at SAGA Space Architecture through MISTI Denmark, designing life support systems for an underwater habitat that will be used for astronaut training and oceanographic research.

Schipper was a member of the Concourse learning community, Sigma Kappa Sorority, and her living group, Burton 3rd. In her free time, she enjoys fixing bicycles and playing the piano.

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Study: Even after learning the right idea, humans and animals still seem to test other approaches

Maybe it’s a life hack or a liability, or a little of both. A surprising result in a new MIT study may suggest that people and animals alike share an inherent propensity to keep updating their approach to a task even when they have already learned how they should approach it, and even if the deviations sometimes lead to unnecessary error.

The behavior of “exploring” when one could just be “exploiting” could make sense for at least two reasons, says Mriganka Sur, senior author of the study published Feb. 18 in Current Biology. Just because a task’s rules seem set one moment doesn’t mean they’ll stay that way in this uncertain world, so altering behavior from the optimal condition every so often could help reveal needed adjustments. Moreover, trying new things when you already know what you like is a way of finding out whether there might be something even better out there than the good thing you’ve got going on right now.

“If the goal is to maximize reward, you should never deviate once you have found the perfect solution, yet you keep exploring,” says Sur, the Paul and Lilah Newton Professor in The Picower Institute for Learning and Memory and the Department of Brain and Cognitive Sciences at MIT. “Why? It’s like food. We all like certain foods, but we still keep trying different foods because you never know, there might be something you could discover.”

Predicting timing

Former research technician Tudor Dragoi, now a graduate student at Boston University, led the study in which he and fellow members of the Sur Lab explored how humans and marmosets, a small primate, make predictions about event timing.

Three humans and two marmosets were given a simple task. They’d see an image on a screen for some amount of time — the amount of time varied from one trial to the next within a limited range — and they simply had to hit a button (marmosets poked a tablet while humans clicked a mouse) when the image disappeared. Success was defined as reacting as quickly as possible to the image’s disappearance without hitting the button too soon. Marmosets received a juice reward on successful trials.

Though marmosets needed more training time than humans, the subjects all settled into the same reasonable pattern of behavior regarding the task. The longer the image stayed on the screen, the faster their reaction time to its disappearance. This behavior follows the “hazard model” of prediction in which, if the image can only last for so long, the longer it’s still there, the more likely it must be to disappear very soon. The subjects learned this and overall, with more experience, their reaction times became faster.

But as the experiment continued, Sur and Dragoi’s team noticed something surprising was also going on. Mathematical modeling of the reaction time data revealed that both the humans and marmosets were letting the results of the immediate previous trial influence what they did on the next trial, even though they had already learned what to do. If the image was only on the screen briefly in one trial, on the next round subjects would decrease reaction time a bit (presumably expecting a shorter image duration again) whereas if the image lingered, they’d increase reaction time (presumably because they figured they’d have a longer wait).

Those results add to ones from a similar study Sur’s lab published in 2023, in which they found that even after mice learned the rules of a different cognitive task, they’d arbitrarily deviate from the winning strategy every so often. In that study, like this one, learning the successful strategy didn’t prevent subjects from continuing to test alternatives, even if it meant sacrificing reward.

“The persistence of behavioral changes even after task learning may reflect exploration as a strategy for seeking and setting on an optimal internal model of the environment,” the scientists wrote in the new study.

Relevance for autism

The similarity of the human and marmoset behaviors is an important finding as well, Sur says. That’s because differences in making predictions about one’s environment is posited to be a salient characteristic of autism spectrum disorders. Because marmosets are small, are inherently social, and are more cognitively complex than mice, work has begun in some labs to establish marmoset autism models, but a key component was establishing that they model autism-related behaviors well. By demonstrating that marmosets model neurotypical human behavior regarding predictions, the study therefore adds weight to the emerging idea that marmosets can indeed provide informative models for autism studies.

In addition to Dragoi and Sur, other authors of the paper are Hiroki Sugihara, Nhat Le, Elie Adam, Jitendra Sharma, Guoping Feng, and Robert Desimone.

The Simons Foundation Autism Research Initiative supported the research through the Simons Center for the Social Brain at MIT.

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High-speed videos show what happens when a droplet splashes into a pool

Rain can freefall at speeds of up to 25 miles per hour. If the droplets land in a puddle or pond, they can form a crown-like splash that, with enough force, can dislodge any surface particles and launch them into the air.

Now MIT scientists have taken high-speed videos of droplets splashing into a deep pool, to track how the fluid evolves, above and below the water line, frame by millisecond frame. Their work could help to predict how spashing droplets, such as from rainstorms and irrigation systems, may impact watery surfaces and aerosolize surface particles, such as pollen on puddles or pesticides in agricultural runoff.

The team carried out experiments in which they dispensed water droplets of various sizes and from various heights into a pool of water. Using high-speed imaging, they measured how the liquid pool deformed as the impacting droplet hit the pool’s surface.

Across all their experiments, they observed a common splash evolution: As a droplet hit the pool, it pushed down below the surface to form a “crater,” or cavity. At nearly the same time, a wall of liquid rose above the surface, forming a crown. Interestingly, the team observed that small, secondary droplets were ejected from the crown before the crown reached its maximum height. This entire evolution happens in a fraction of a second.

Scientists have caught snapshots of droplet splashes in the past, such as the famous “Milk Drop Coronet” — a photo of a drop of milk in mid-splash, taken by the late MIT professor Harold “Doc” Edgerton, who invented a photographic technique to capture quickly moving objects.

The new work represents the first time scientists have used such high-speed images to model the entire splash dynamics of a droplet in a deep pool, combining what happens both above and below the surface. The team has used the imaging to gather new data central to build a mathematical model that predicts how a droplet’s shape will morph and merge as it hits a pool’s surface. They plan to use the model as a baseline to explore to what extent a splashing droplet might drag up and launch particles from the water pool.

“Impacts of drops on liquid layers are ubiquitous,” says study author Lydia Bourouiba, a professor in the MIT departments of Civil and Environmental Engineering and Mechanical Engineering, and a core member of the Institute for Medical Engineering and Science (IMES). “Such impacts can produce myriads of secondary droplets that could act as carriers for pathogens, particles, or microbes that are on the surface of impacted pools or contaminated water bodies. This work is key in enabling prediction of droplet size distributions, and potentially also what such drops can carry with them.”

Bourouiba and her mentees have published their results in the Journal of Fluid Mechanics. MIT co-authors include former graduate student Raj Dandekar PhD ’22, postdoc (Eric) Naijian Shen, and student mentee Boris Naar.

Above and below

At MIT, Bourouiba heads up the Fluid Dynamics of Disease Transmission Laboratory, part of the Fluids and Health Network, where she and her team explore the fundamental physics of fluids and droplets in a range of environmental, energy, and health contexts, including disease transmission. For their new study, the team looked to better understand how droplets impact a deep pool — a seemingly simple phenomenon that nevertheless has been tricky to precisely capture and characterize.

Bourouiba notes that there have been recent breakthroughs in modeling the evolution of a splashing droplet below a pool’s surface. As a droplet hits a pool of water, it breaks through the surface and drags air down through the pool to create a short-lived crater. Until now, scientists have focused on the evolution of this underwater cavity, mainly for applications in energy harvesting. What happens above the water, and how a droplet’s crown-like shape evolves with the cavity below, remained less understood.

“The descriptions and understanding of what happens below the surface, and above, have remained very much divorced,” says Bourouiba, who believes such an understanding can help to predict how droplets launch and spread chemicals, particles, and microbes into the air.

Splash in 3D

To study the coupled dynamics between a droplet’s cavity and crown, the team set up an experiment to dispense water droplets into a deep pool. For the purposes of their study, the researchers considered a deep pool to be a body of water that is deep enough that a splashing droplet would remain far away from the pool’s bottom. In these terms, they found that a pool with a depth of at least 20 centimeters was sufficient for their experiments.

They varied each droplet’s size, with an average diameter of about 5 millimeters. They also dispensed droplets from various heights, causing the droplets to hit the pool’s surface at different speeds, which on average was about 5 meters per second. The overall dynamics, Bourouiba says, should be similar to what occurs on the surface of a puddle or pond during an average rainstorm.

“This is capturing the speed at which raindrops fall,” she says. “These wouldn’t be very small, misty drops. This would be rainstorm drops for which one needs an umbrella.”

Using high-speed imaging techniques inspired by Edgerton’s pioneering photography, the team captured videos of pool-splashing droplets, at rates of up to 12,500 frames per second. They then applied in-house imaging processing methods to extract key measurements from the image sequences, such as the changing width and depth of the underwater cavity, and the evolving diameter and height of the rising crown. The researchers also captured especially tricky measurements, of the crown’s wall thickness profile and inner flow — the cylinder that rises out of the pool, just before it forms a rim and points that are characteristic of a crown.

“This cylinder-like wall of rising liquid, and how it evolves in time and space, is at the heart of everything,” Bourouiba says. “It’s what connects the fluid from the pool to what will go into the rim and then be ejected into the air through smaller, secondary droplets.”

The researchers worked the image data into a set of “evolution equations,” or a mathematical model that relates the various properties of an impacting droplet, such as the width of its cavity and the thickness and speed profiles of its crown wall, and how these properties change over time, given a droplet’s starting size and impact speed.

“We now have a closed-form mathematical expression that people can use to see how all these quantities of a splashing droplet change over space and time,” says co-author Shen, who plans, with Bourouiba, to apply the new model to the behavior of secondary droplets and understanding how a splash end-up dispersing particles such as pathogens and pesticides. “This opens up the possibility to study all these problems of splash in 3D, with self-contained closed-formed equations, which was not possible before.”

This research was supported, in part, by the Department of Agriculture-National Institute of Food and Agriculture Specialty Crop Research Initiative; the Richard and Susan Smith Family Foundation; the National Science Foundation; the Centers for Disease Control and Prevention-National Institute for Occupational Safety and Health; Inditex; and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.

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Rooftop panels, EV chargers, and smart thermostats could chip in to boost power grid resilience

There’s a lot of untapped potential in our homes and vehicles that could be harnessed to reinforce local power grids and make them more resilient to unforeseen outages, a new study shows.

In response to a cyber attack or natural disaster, a backup network of decentralized devices — such as residential solar panels, batteries, electric vehicles, heat pumps, and water heaters — could restore electricity or relieve stress on the grid, MIT engineers say.

Such devices are “grid-edge” resources found close to the consumer rather than near central power plants, substations, or transmission lines. Grid-edge devices can independently generate, store, or tune their consumption of power. In their study, the research team shows how such devices could one day be called upon to either pump power into the grid, or rebalance it by dialing down or delaying their power use.

In a paper appearing this week in the Proceedings of the National Academy of Sciences, the engineers present a blueprint for how grid-edge devices could reinforce the power grid through a “local electricity market.” Owners of grid-edge devices could subscribe to a regional market and essentially loan out their device to be part of a microgrid or a local network of on-call energy resources.

In the event that the main power grid is compromised, an algorithm developed by the researchers would kick in for each local electricity market, to quickly determine which devices in the network are trustworthy. The algorithm would then identify the combination of trustworthy devices that would most effectively mitigate the power failure, by either pumping power into the grid or reducing the power they draw from it, by an amount that the algorithm would calculate and communicate to the relevant subscribers. The subscribers could then be compensated through the market, depending on their participation.

The team illustrated this new framework through a number of grid attack scenarios, in which they considered failures at different levels of a power grid, from various sources such as a cyber attack or a natural disaster. Applying their algorithm, they showed that various networks of grid-edge devices were able to dissolve the various attacks.

The results demonstrate that grid-edge devices such as rooftop solar panels, EV chargers, batteries, and smart thermostats (for HVAC devices or heat pumps) could be tapped to stabilize the power grid in the event of an attack.

“All these small devices can do their little bit in terms of adjusting their consumption,” says study co-author Anu Annaswamy, a research scientist in MIT’s Department of Mechanical Engineering. “If we can harness our smart dishwashers, rooftop panels, and EVs, and put our combined shoulders to the wheel, we can really have a resilient grid.”

The study’s MIT co-authors include lead author Vineet Nair and John Williams, along with collaborators from multiple institutions including the Indian Institute of Technology, the National Renewable Energy Laboratory, and elsewhere.

Power boost

The team’s study is an extension of their broader work in adaptive control theory and designing systems to automatically adapt to changing conditions. Annaswamy, who leads the Active-Adaptive Control Laboratory at MIT, explores ways to boost the reliability of renewable energy sources such as solar power.

“These renewables come with a strong temporal signature, in that we know for sure the sun will set every day, so the solar power will go away,” Annaswamy says. “How do you make up for the shortfall?”

The researchers found the answer could lie in the many grid-edge devices that consumers are increasingly installing in their own homes.

“There are lots of distributed energy resources that are coming up now, closer to the customer rather than near large power plants, and it’s mainly because of individual efforts to decarbonize,” Nair says. “So you have all this capability at the grid edge. Surely we should be able to put them to good use.”

While considering ways to deal with drops in energy from the normal operation of renewable sources, the team also began to look into other causes of power dips, such as from cyber attacks. They wondered, in these malicious instances, whether and how the same grid-edge devices could step in to stabilize the grid following an unforeseen, targeted attack.

Attack mode

In their new work, Annaswamy, Nair, and their colleagues developed a framework for incorporating grid-edge devices, and in particular, internet-of-things (IoT) devices, in a way that would support the larger grid in the event of an attack or disruption. IoT devices are physical objects that contain sensors and software that connect to the internet.

For their new framework, named EUREICA (Efficient, Ultra-REsilient, IoT-Coordinated Assets), the researchers start with the assumption that one day, most grid-edge devices will also be IoT devices, enabling rooftop panels, EV chargers, and smart thermostats to wirelessly connect to a larger network of similarly independent and distributed devices. 

The team envisions that for a given region, such as a community of 1,000 homes, there exists a certain number of IoT devices that could potentially be enlisted in the region’s local network, or microgrid. Such a network would be managed by an operator, who would be able to communicate with operators of other nearby microgrids.

If the main power grid is compromised or attacked, operators would run the researchers’ decision-making algorithm to determine trustworthy devices within the network that can pitch in to help mitigate the attack.

The team tested the algorithm on a number of scenarios, such as a cyber attack in which all smart thermostats made by a certain manufacturer are hacked to raise their setpoints simultaneously to a degree that dramatically alters a region’s energy load and destabilizes the grid. The researchers also considered attacks and weather events that would shut off the transmission of energy at various levels and nodes throughout a power grid.

“In our attacks we consider between 5 and 40 percent of the power being lost. We assume some nodes are attacked, and some are still available and have some IoT resources, whether a battery with energy available or an EV or HVAC device that’s controllable,” Nair explains. “So, our algorithm decides which of those houses can step in to either provide extra power generation to inject into the grid or reduce their demand to meet the shortfall.”

In every scenario that they tested, the team found that the algorithm was able to successfully restabilize the grid and mitigate the attack or power failure. They acknowledge that to put in place such a network of grid-edge devices will require buy-in from customers, policymakers, and local officials, as well as innovations such as advanced power inverters that enable EVs to inject power back into the grid.

“This is just the first of many steps that have to happen in quick succession for this idea of local electricity markets to be implemented and expanded upon,” Annaswamy says. “But we believe it’s a good start.”

This work was supported, in part, by the U.S. Department of Energy and the MIT Energy Initiative.

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MIT biologists discover a new type of control over RNA splicing

RNA splicing is a cellular process that is critical for gene expression. After genes are copied from DNA into messenger RNA, portions of the RNA that don’t code for proteins, called introns, are cut out and the coding portions are spliced back together.

This process is controlled by a large protein-RNA complex called the spliceosome. MIT biologists have now discovered a new layer of regulation that helps to determine which sites on the messenger RNA molecule the spliceosome will target.

The research team discovered that this type of regulation, which appears to influence the expression of about half of all human genes, is found throughout the animal kingdom, as well as in plants. The findings suggest that the control of RNA splicing, a process that is fundamental to gene expression, is more complex than previously known.

“Splicing in more complex organisms, like humans, is more complicated than it is in some model organisms like yeast, even though it’s a very conserved molecular process. There are bells and whistles on the human spliceosome that allow it to process specific introns more efficiently. One of the advantages of a system like this may be that it allows more complex types of gene regulation,” says Connor Kenny, an MIT graduate student and the lead author of the study.

Christopher Burge, the Uncas and Helen Whitaker Professor of Biology at MIT, is the senior author of the study, which appears today in Nature Communications.

Building proteins

RNA splicing, a process discovered in the late 1970s, allows cells to precisely control the content of the mRNA transcripts that carry the instructions for building proteins.

Each mRNA transcript contains coding regions, known as exons, and noncoding regions, known as introns. They also include sites that act as signals for where splicing should occur, allowing the cell to assemble the correct sequence for a desired protein. This process enables a single gene to produce multiple proteins; over evolutionary timescales, splicing can also change the size and content of genes and proteins, when different exons become included or excluded.

The spliceosome, which forms on introns, is composed of proteins and noncoding RNAs called small nuclear RNAs (snRNAs). In the first step of spliceosome assembly, an snRNA molecule known as U1 snRNA binds to the 5’ splice site at the beginning of the intron. Until now, it had been thought that the binding strength between the 5’ splice site and the U1 snRNA was the most important determinant of whether an intron would be spliced out of the mRNA transcript.

In the new study, the MIT team discovered that a family of proteins called LUC7 also helps to determine whether splicing will occur, but only for a subset of introns — in human cells, up to 50 percent.

Before this study, it was known that LUC7 proteins associate with U1 snRNA, but the exact function wasn’t clear. There are three different LUC7 proteins in human cells, and Kenny’s experiments revealed that two of these proteins interact specifically with one type of 5’ splice site, which the researchers called “right-handed.” A third human LUC7 protein interacts with a different type, which the researchers call “left-handed.”

The researchers found that about half of human introns contain a right- or left-handed site, while the other half do not appear to be controlled by interaction with LUC7 proteins. This type of control appears to add another layer of regulation that helps remove specific introns more efficiently, the researchers say.

“The paper shows that these two different 5’ splice site subclasses exist and can be regulated independently of one another,” Kenny says. “Some of these core splicing processes are actually more complex than we previously appreciated, which warrants more careful examination of what we believe to be true about these highly conserved molecular processes.”

“Complex splicing machinery”

Previous work has shown that mutation or deletion of one of the LUC7 proteins that bind to right-handed splice sites is linked to blood cancers, including about 10 percent of acute myeloid leukemias (AMLs). In this study, the researchers found that AMLs that lost a copy of the LUC7L2 gene have inefficient splicing of right-handed splice sites. These cancers also developed the same type of altered metabolism seen in earlier work.

“Understanding how the loss of this LUC7 protein in some AMLs alters splicing could help in the design of therapies that exploit these splicing differences to treat AML,” Burge says. “There are also small molecule drugs for other diseases such as spinal muscular atrophy that stabilize the interaction between U1 snRNA and specific 5’ splice sites. So the knowledge that particular LUC7 proteins influence these interactions at specific splice sites could aid in improving the specificity of this class of small molecules.”

Working with a lab led by Sascha Laubinger, a professor at Martin Luther University Halle-Wittenberg, the researchers found that introns in plants also have right- and left-handed 5’ splice sites that are regulated by Luc7 proteins.

The researchers’ analysis suggests that this type of splicing arose in a common ancestor of plants, animals, and fungi, but it was lost from fungi soon after they diverged from plants and animals.

“A lot what we know about how splicing works and what are the core components actually comes from relatively old yeast genetics work,” Kenny says. “What we see is that humans and plants tend to have more complex splicing machinery, with additional components that can regulate different introns independently.”

The researchers now plan to further analyze the structures formed by the interactions of Luc7 proteins with mRNA and the rest of the spliceosome, which could help them figure out in more detail how different forms of Luc7 bind to different 5’ splice sites.

The research was funded by the U.S. National Institutes of Health and the German Research Foundation.

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Chip-based system for terahertz waves could enable more efficient, sensitive electronics

The use of terahertz waves, which have shorter wavelengths and higher frequencies than radio waves, could enable faster data transmission, more precise medical imaging, and higher-resolution radar.

But effectively generating terahertz waves using a semiconductor chip, which is essential for incorporation into electronic devices, is notoriously difficult.

Many current techniques can’t generate waves with enough radiating power for useful applications unless they utilize bulky and expensive silicon lenses. Higher radiating power allows terahertz signals to travel farther. Such lenses, which are often larger than the chip itself, make it hard to integrate the terahertz source into an electronic device.

To overcome these limitations, MIT researchers developed a terahertz amplifier-multiplier system that achieves higher radiating power than existing devices without the need for silicon lenses.

By affixing a thin, patterned sheet of material to the back of the chip and utilizing higher-power Intel transistors, the researchers produced a more efficient, yet scalable, chip-based terahertz wave generator.

This compact chip could be used to make terahertz arrays for applications like improved security scanners for detecting hidden objects or environmental monitors for pinpointing airborne pollutants.

“To take full advantage of a terahertz wave source, we need it to be scalable. A terahertz array might have hundreds of chips, and there is no place to put silicon lenses because the chips are combined with such high density. We need a different package, and here we’ve demonstrated a promising approach that can be used for scalable, low-cost terahertz arrays,” says Jinchen Wang, a graduate student in the Department of Electrical Engineering and Computer Science (EECS) and lead author of a paper on the terahertz radiator.

He is joined on the paper by EECS graduate students Daniel Sheen and Xibi Chen; Steven F. Nagel, managing director of the T.J. Rodgers RLE Laboratory; and senior author Ruonan Han, an associate professor in EECS, who leads the Terahertz Integrated Electronics Group. The research will be presented at the IEEE International Solid-States Circuits Conference.

Making waves

Terahertz waves sit on the electromagnetic spectrum between radio waves and infrared light. Their higher frequencies enable them to carry more information per second than radio waves, while they can safely penetrate a wider range of materials than infrared light.

One way to generate terahertz waves is with a CMOS chip-based amplifier-multiplier chain that increases the frequency of radio waves until they reach the terahertz range. To achieve the best performance, waves go through the silicon chip and are eventually emitted out the back into the open air.

But a property known as the dielectric constant gets in the way of a smooth transmission.

The dielectric constant influences how electromagnetic waves interact with a material. It affects the amount of radiation that is absorbed, reflected, or transmitted. Because the dielectric constant of silicon is much higher than that of air, most terahertz waves are reflected at the silicon-air boundary rather than being cleanly transmitted out the back.

Since most signal strength is lost at this boundary, current approaches often use silicon lenses to boost the power of the remaining signal. 

The MIT researchers approached this problem differently.

They drew on an electromechanical theory known as matching. With matching, they seek to equal out the dielectric constants of silicon and air, which will minimize the amount of signal that is reflected at the boundary.

They accomplish this by sticking a thin sheet of material which has a dielectric constant between silicon and air to the back of the chip. With this matching sheet in place, most waves will be transmitted out the back rather than being reflected.

A scalable approach

They chose a low-cost, commercially available substrate material with a dielectric constant very close to what they needed for matching. To improve performance, they used a laser cutter to punch tiny holes into the sheet until its dielectric constant was exactly right.

“Since the dielectric constant of air is 1, if you just cut some subwavelength holes in the sheet, it is equivalent to injecting some air, which lowers the overall dielectric constant of the matching sheet,” Wang explains.

In addition, they designed their chip with special transistors developed by Intel that have a higher maximum frequency and breakdown voltage than traditional CMOS transistors.

“These two things taken together, the more powerful transistors and the dielectric sheet, plus a few other small innovations, enabled us to outperform several other devices,” he says.

Their chip generated terahertz signals with a peak radiation power of 11.1 decibel-milliwatts, the best among state-of-the-art techniques. Moreover, since the low-cost chip can be fabricated at scale, it could be integrated into real-world electronic devices more readily.

One of the biggest challenges of developing a scalable chip was determining how to manage the power and temperature when generating terahertz waves.

“Because the frequency and the power are so high, many of the standard ways to design a CMOS chip are not applicable here,” Wang says.

The researchers also needed to devise a technique for installing the matching sheet that could be scaled up in a manufacturing facility.

Moving forward, they want to demonstrate this scalability by fabricating a phased array of CMOS terahertz sources, enabling them to steer and focus a powerful terahertz beam with a low-cost, compact device.

This research is supported, in part, by NASA’s Jet Propulsion Laboratory and Strategic University Research Partnerships Program, as well as the MIT Center for Integrated Circuits and Systems. The chip was fabricated through the Intel University Shuttle Program.

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Cynthia Barnhart to step down as provost

Cynthia Barnhart SM ’86, PhD ’88 will step down as MIT’s provost, effective July 1, President Sally Kornbluth announced today. Barnhart, who served as MIT’s chancellor for more than seven years before becoming provost in 2022, will return to the faculty following a sabbatical.

Barnhart led a variety of efforts to enhance academics and research at the Institute during her tenure as provost, which bridged a transition between two MIT presidents. She drew from deep-rooted experience in the MIT community, first as a graduate student and then as a faculty member for more than 30 years, serving in the Department of Civil and Environmental Engineering and in the MIT Sloan School of Management, with affiliations in the Operations Research Center and the Center for Transportation and Logistics.

Barnhart is only the second MIT administrator, following Julius Stratton, to serve as both chancellor and provost. She is also the first woman to serve in each of these roles.

“It has been a privilege to serve and to support our community’s efforts to lead in education, research, and impact in the world,” Barnhart says.

MIT’s provost is the Institute’s chief academic and budget officer, responsible for leading efforts to establish academic priorities, managing financial planning and research support, and overseeing MIT’s international engagements. The provost works closely with the president, school and college deans, vice provosts, executive vice president and treasurer (EVPT), faculty officers, and many other leaders to recruit and retain the best talent and then, as Barnhart puts it, “create the conditions for them to thrive and do their best work at MIT.”

“Cindy has been a wonderful partner in thinking and doing, and I will be forever grateful for having been able to tap her knowledge of the Institute’s people, culture, practices and institutional systems,” Kornbluth wrote in an email to the MIT community.

The next chapter

L. Rafael Reif named Barnhart provost as he was stepping down as MIT’s 17th president, citing her “values, skills, vision, and collaborative spirit.” Her appointment provided the Institute with continuity and helped to sustain momentum during the transition and the first years of Kornbluth’s presidency.

“A good provost is constantly solving problems over the widest range of scales, thinking at the level of systems and structures but also digging deep when needed. Cindy has brought discipline, commitment, and heart to this role, and it's been a privilege to work with her,” says Faculty Chair Mary Fuller.

As she proceeds with a long-planned sabbatical, Barnhart will focus on a project she has been working on as provost. The effort centers around creating a flexible, affordable educational experience and curriculum in order to dramatically increase the size of the nation’s science- and technology-based workforce.

Creating conditions for faculty to thrive

As chief budget officer, Barnhart worked closely with EVPT Glen Shor, Vice President for Finance Katie Hammer, and colleagues across the Institute to provide essential resources for the Institute’s education and research enterprises. She cites as points of pride implementing new central support for MIT’s under-recovery system, closing the NASA and U.S. National Science Foundation (NSF) fellowship tuition and stipend shortfalls, and expanding the number of Office of the Provost professorship chairs to 230, an increase of more than 20 percent.

“The review of the Institute’s budget process that we launched last year is critical to the Institute’s effective response to emerging financial constraints,” Barnhart says.

“It’s about providing our community with access to the tools needed to develop strategic, creative ways to deploy our resources so that, even in the face of budget challenges, we can help people do what they came here to do — discover, invent, innovate, and problem solve, all in service to the nation and the world,” she says.

Responding to calls for more faculty involvement in searches to identify faculty leaders in the Office of the Provost, Barnhart established best practices for search advisory committees. Over the course of her tenure, these faculty-led groups assisted with the appointments of Vice Provost for Faculty Paula Hammond, Vice Provost for Open Learning Dimitris Bertsimas, Vice Provost for International Activities Duane Boning, MIT Sloan School of Management Dean Rick Locke, and Interim CEO and Director of the Singapore-MIT Alliance for Research and Technology (SMART) Bruce Tidor. In addition, Barnhart convened a search committee to identify a new leader to steward MIT’s research enterprise, which informed President Kornbluth’s appointment of Vice President for Research Ian A. Waitz last year.

“MIT’s next provost is going to be working with an exceptional team,” says Barnhart. “The Provost’s Office is positioned to ensure the faculty have what they need to make big impacts in research and education.”

Barnhart took several steps to provide her leadership team and faculty more broadly with professional development and career advancement opportunities. She standardized appointment and reappointment terms, created 360-degree feedback mechanisms, and formalized reappointment review processes for deans and vice provosts. In partnership with Hammond, new programs were launched on establishing positive department climates, generating impactful research funding proposals, and fostering effective graduate student mentoring.

“Cindy has always cared greatly about the faculty experience, and this deep regard is evident in all that she has done,” Hammond says. “She has sought to understand how we might better build a supportive environment that fosters faculty success and has invested in meaningful programs and policies that help to address faculty needs while developing tools for faculty to accomplish their professional and leadership goals.”

Barnhart and Hammond also partnered with Fuller, the MIT Institutional Research team, and other colleagues to assess MIT’s progress on addressing the findings of two landmark reports: the 1999 Study on the Status of Women Faculty in Science at MIT and the 2010 Report on the Initiative for Faculty Race and Diversity.

Barnhart shared the group’s analysis and corresponding response plan with the entire faculty. In her message, Barnhart highlighted how “the original reports’ power sprang from the rigorous analysis the authors conducted and from how openly our community reflected on the problems they identified. For MIT to foster the diverse breadth of faculty excellence that is critical to our mission, we need that same collective embrace of data and transparency, dialogue and action again.”

Advancing 21st-century education and research

Barnhart is committed to making MIT’s education accessible and affordable to a much broader set of learners. With Bertsimas, Barnhart launched the next phase of MIT Open Learning, which involves ambitious plans to extend MIT’s commitment to providing global access to the Institute’s brand of education.

“With her good judgement, open mindedness, passion for quality education in the world, and love and deep knowledge of MIT, Cindy has been a great partner in reshaping the strategy for open learning,” Bertsimas says. “I look forward to continuing our partnership in the years to come.”

As computing has become increasingly integral to many disciplines, the creation of interdisciplinary computing courses through The Common Ground, degrees that blend computing with another field, and interdisciplinary computing faculty hires have expanded the forefront of MIT education and research. With Barnhart as a strong champion, the MIT Schwarzman College of Computing has been at the center of these efforts.

“Embracing the college’s efforts to broaden and deepen MIT’s world-leading strengths in interdisciplinary education and research is, simply put, in Barnhart’s DNA,” says Dan Huttenlocher, dean of the MIT Schwarzman College of Computing.

By design, the Institute’s strategic initiatives in climate, humanities, and life sciences also lean into this interdisciplinary approach. Barnhart worked alongside Kornbluth, Chief Innovation and Strategy Officer Anantha Chandrakasan, and many other faculty on the development of these efforts throughout her tenure.

“It has been a privilege working with Provost Barnhart and President Kornbluth to advance the Institute’s wide range of strategic initiatives,” says Chandrakasan. “With a sense of urgency that these initiatives demand, Provost Barnhart was instrumental in defining the vision for these missions, promoting broad engagement from the MIT community and beyond while paving critical pathways for seed funding and fundraising. It would have been impossible to launch these initiatives without her inspiring ideas, creative solutions, and incredible support.”

A systems thinker

After earning her PhD in transportation systems in 1988 at MIT, Barnhart joined the operations research faculty at the School of Industrial and Systems Engineering at Georgia Tech. She returned to MIT four years later in 1992 and has been at the Institute ever since. Her research, which she has continued throughout her time in leadership roles, focuses on the development of optimization models and methods for designing, planning, and operating transportation systems.

“I’m a systems thinker, an optimizer, and a problem solver,” Barnhart says. “That is one of the reasons I have enjoyed serving as provost, a role in which there certainly is no shortage of opportunity to apply my decision-making and problem-solving mindset.”

Barnhart became associate dean of the MIT School of Engineering in 2007 and served as acting dean in 2010-2011. As chancellor, she was responsible for “all things students” at MIT, including student life, undergraduate admissions, graduate student support, the first-year educational experience, and more. She also participated in strategic planning, faculty appointments, resource development, and campus planning as chancellor.

Barnhart has been an undergraduate adviser and has supervised graduate and undergraduate theses of students across the Institute, including in the departments of Civil and Environmental Engineering, Aeronautics and Astronautics, Mechanical Engineering, and Electrical Engineering and Computer Science; in the Engineering Systems Division; in the MIT Sloan School of Management; in the Operations Research Center; and in the Center for Transportation and Logistics. She has taught subjects jointly listed in these units on optimization and operations research, with applications to transportation operations, planning, and control.

Kornbluth will work with a group of faculty members drawn from each school and the college to help her in selecting the next provost. 

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