MIT professor devises new ways to generate useful chemicals and fuels from renewable resources.
MIT Profile Roman PRESS Web
Newly tenured MIT Department of Chemical Engineering faculty member Yuriy Roman says, "The most rewarding aspect of my profession is to work with these extremely talented and bright students. Image, M. Scott Brauer.

A couple of years into graduate school, Yuriy Roman had what he calls a “tipping point” in his career. He realized that all of the classes he had taken were leading him toward a deep understanding of the concepts he needed to design his own solutions to chemical problems.

“All the classes I had taken suddenly came together, and that’s when I started understanding why I needed to know something about thermodynamics, kinetics, and transport. All of these concepts that I had seen as more theoretical things in my classes, I could now see being applied together to solve a problem. That really was what changed everything for me,” he says.

As a newly tenured faculty member in MIT’s Department of Chemical Engineering, Roman now tries to guide his students toward their own tipping points.
“It’s amazing to see it happen with my students,” says Roman, noting that working with students is one of his favorite things about being an MIT professor. His students also make major contributions to his lab’s mission: coming up with new catalysts to produce fuels, plastics, and other useful substances in a more efficient, sustainable manner.

“To me, the most rewarding aspect of my profession is to work with these extremely talented and bright students,” Roman says. “They really are great at coming up with outside-of-the-box concepts, and I love that. I think MIT’s biggest asset is precisely that, the students. To me it’s a pleasure to work with them and learn from them as well, and hopefully have the opportunity to teach them some of the things that I know.”

Chemical synthesis

Roman, who grew up in Mexico City, loved chemistry from a young age. “I just liked to play with things like soap and bleach, which maybe wasn’t the safest thing,” he recalls. Another favorite activity was juicing cabbages to produce a pH indicator. (Red cabbage contains a chemical called anthocyanin that changes color when exposed to acidic or basic environments.)

Roman’s mother was originally from Belarus, and with his multicultural background he developed a strong interest in learning about other cultures and visiting other countries. He won a full scholarship to Monterrey Institute of Technology and Higher Education, in Mexico, for high school and college, but during his first year of college, he became interested in going abroad to finish his degree.

A friend who was then an undergraduate at MIT encouraged Roman to apply to schools in the United States, and he ended up transferring to the University of Pennsylvania.

“My parents were very surprised. In Mexico, it is common to live with your parents long after finishing college. The concept of leaving for college is almost nonexistent,” Roman says.

Roman decided to study chemical engineering, allowing him to combine his love for chemical reactions and his desire to follow in the footsteps of a brother who was an engineer. After graduating, he planned to look for a job in the chemical industry, but his then-girlfriend, now his wife, was planning to begin medical school. She suggested that he go to graduate school with her, so they both ended up attending the University of Wisconsin at Madison.

There, Roman studied with James Dumesic, a chemistry professor who works on biofuels. For his PhD thesis, Roman devised a process to generate a chemical called hydroxymethylfurfural (HMF) from sugars derived from biomass. HMF is a “platform chemical” that can be converted into many different end products, including fuels.

After finishing graduate school, Roman thought he would go to work for a chemical company, but at Dumesic’s suggestion he decided to go into academia instead.
“When I started interviewing at different universities, I realized that as a professor, you can have a lot of freedom to explore ideas and tackle problems long-term, and you can still have a lot of contact with industry,” he says. “You have more control over your time and where you spend it, in terms of investing effort toward basic science.”

Out of graduate school, he got a job offer at MIT but first spent two years doing a postdoc at Caltech, while his wife did her residency at the University of California at Los Angeles. Working with Mark Davis, a professor of chemical engineering, Roman began studying materials called zeolites, which have pores the same size as many common molecules. Confining molecules in these pores allows for certain chemical reactions to occur much faster than they otherwise would, Roman says.

Davis also instilled in Roman the importance of designing his own catalysts rather than relying on those developed by others, which allows for more control over chemical reactions and the resulting materials. While many research groups focus either on designing catalysts or on using existing catalysts to come up with novel ways to synthesize materials, Roman believes it is critical to work on both. 

“When you are in control of synthesizing your own catalysts, you can do much more systematic studies. You have the ability to manipulate things at will,” he says. “It’s working at this juncture of synthesis and catalysis that is the key to discovering new chemistry.”

Green chemistry

After arriving at MIT in 2010, Roman launched his lab with a focus on designing catalysts that can generate new and interesting materials. One key area of research is the conversion of biomass components, such as lignin, into fuels and chemicals. One of the biggest challenges in this type of synthesis is to selectively remove oxygen atoms from these molecules, which usually have many more oxygen atoms than fuels do.

During a brainstorming session, Roman and his students came up with the idea of using a metal oxide catalyst in which some oxygen atoms were removed from the surface, creating small pockets known as “vacancies.” Oxygenated molecules can be precisely anchored in those vacancies, allowing their carbon-oxygen bonds to be easily broken so the oxygen can be replaced with hydrogen.

In another project, Roman’s lab developed a more sustainable alternative to catalysts made from precious metals such as platinum and palladium. These metals are used in many renewable-energy technologies, including fuel cells and lithium-air batteries, but they are among the Earth’s scarcest metals.

“If we were to go from our current fleet of vehicles with internal combustion engines to a fuel cell fleet, there’s not enough platinum in the world to sustain that amount,” Roman says. “You need to use Earth-abundant materials because there simply aren’t enough of these other precious materials to do it.”

In 2014, Roman and his students showed that they could create powerful catalysts from compounds called metal carbides, made from plentiful metals such as tungsten, coated with just a thin layer of a rare metal such as platinum.

Developing and promoting this kind of sustainable technology is one of Roman’s biggest research priorities.

“It’s a tremendous battle because the energy sector is just so large. The scale is so big and the infrastructure that’s already in place for petroleum-based fuel is so extensive. But it’s important for us to develop technologies for renewable resources and really curb our emissions of greenhouse gases,” he says. “Big, hard problems. That’s what we’re going after.”

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Anne Trafton | MIT News Office
March 22, 2018

MIT engineers develop a way to triple the survival time for swimmers in wetsuits.

When Navy SEALs carry out dives in Arctic waters, or when rescue teams are diving under ice-covered rivers or ponds, the survival time even in the best wetsuits is very limited – as little as tens of minutes, and the experience can be extremely painful at best. Finding ways of extending that survival time without hampering mobility has been a priority for the U.S. Navy and research divers, as a pair of MIT engineering professors learned during a recent program that took them to a variety of naval facilities.

That visit led to a two-year collaboration that has now yielded a dramatic result: a simple treatment that can improve the survival time for a conventional wetsuit by a factor of three, the scientists say.

A simple treatment that can improve the survival time for a conventional wetsuit by a factor of three, MIT scientists say.
A simple treatment can improve the survival time for a conventional wetsuit by a factor of three, MIT scientists say.

The findings, which could be applied essentially immediately, are reported June 18, 2018, in the journal RSC Advances, in a paper by Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering; Jacopo Buongiorno, the TEPCO Professor and associate head of the Department of Nuclear Science and Engineering; and five others at MIT and George Mason University.

The process they discovered works by simply placing the standard neoprene wetsuit inside a pressure tank autoclave no bigger than a beer keg, filled with a heavy inert gas, for about a day. The treatment then lasts for about 20 hours, far longer than anyone would spend on a dive, explains Buongiorno, who is an avid wetsuit user himself. [He competed in a triathlon just last week.] The process could also be done in advance, with the wetsuit placed in a sealed bag to be opened just before use, he says.

Though Buongiorno and Strano are both on the MIT faculty, they had never met until they were both part of the Defense Science Study Group for the Department of Defense. “We got to visit a lot of bases, and met with all kinds of military people up to four-star generals,” says Buongiorno, whose specialty in nuclear engineering has to do with heat transfer, especially through water. They learned about the military’s particular needs and were asked to design a technological project to address one of those needs. After meeting with a group of Navy SEALs, the elite special-operations diving corps, they decided the need for longer-lasting protection in icy waters was one that they could take on.

They looked at the different strategies that various animals use to survive in these frigid waters, and found three types: air pockets trapped in fur or feathers, as with otters and penguins; internally generated heat, as with some animals and fish [including great white sharks, which, surprisingly, are warm-blooded]; or a layer of insulating material that greatly slows heat loss from the body, as with seals’ and whales’ blubber.

In the end, after simulations and lab tests, they ended up with a combination of two of these — a blubber-like insulating material that also makes use of trapped pockets of gas, although in this case the gas is not air but a heavy inert gas, namely xenon or krypton.

The material that has become standard for wetsuits is neoprene, an inexpensive material that is a mix of synthetic rubber materials processed into a kind of foam, producing a closed-cell structure similar to styrofoam. Trapped within that structure, occupying more than two-thirds of the volume and accounting for half of the heat that gets transferred through it, are pockets of air. 

Strano and Buongiorno found that if the trapped air is replaced with xenon or krypton, the material’s insulating properties increase dramatically. The result, they say, is a material with the lowest heat transfer of any wetsuit ever made. “We set a world record for the world’s lowest thermal conductivity garment,” Strano says – conductivity almost as low as air itself. “It’s like wearing a coat of air.”

MIT Artificial Blubber 01 Web
From left, graduate student Anton Cottrill, Professor Jacopo Buongiorno and Professor Michael Strano try out their neoprene wetsuits at a pool at MIT’s athletic center. Cottrill is holding the pressure tank used to treat the wetsuits with xenon or krypton. Photo, Susan Young

They found this could improve survivability in water colder than 10 degrees Celsius, raising it from less than one hour to two or three hours.

The result could be a boon not just to those in the most extreme environments, but to anyone who uses wetsuits in cold waters, including swimmers, athletes, and surfers, as well as professional divers of all kinds.

“As part of this project, I interviewed dozens of wetsuit users, including a professional underwater photographer, divers working at the New England Aquarium, a Navy SEAL friend of mine, and random surfers I approached on a San Diego beach,” says co-author and former MIT postdoc Jeffrey Moran PhD ’17, who is now an assistant professor at George Mason University. “The feedback was essentially unanimous — there is an urgent need for warmer wetsuits, both in and out of the Arctic. People's eyes lit up when I told them about our results.”

Currently, the only viable cold-water alternatives to wetsuits are dry suits, which have a layer of air between the suit and the skin that must be maintained using a hose and a pump, or a warm-water suit, which similarly requires a hose and pump connection. In either case, a failure of the pump or a cut or tear in the suit can result is a quick loss of insulation that can be life threatening within minutes.

But the xenon- or krypton-infused neoprene requires no such support system and has no way of quickly losing its insulating properties, and so does not carry that risk. “We can take anyone’s neoprene wetsuit and pressurize it with xenon or krypton for high-performance operations,” Strano says. MIT graduate student Anton Cottrill, a co-author of the paper, adds, “The gas actually infuses more quickly during treatment than it discharges during its use in an aquatic environment.”

Another possibility, they say, is to produce a wetsuit with the same insulating properties as present ones, but with a small fraction of the thickness, allowing more comfort and freedom of movement that might be appealing to athletes. “Almost everyone I interviewed also said they wanted a wetsuit that was easier to move around in and to put on and take off,” says Moran. “The results of this project suggest that we could make wetsuits that provide the same thermal insulation as traditional ones, but are about half as thick.”

One next step in their research is to look at ways of making a long-term, stable version of a xenon-infused neoprene, perhaps by bonding a protective layer over it, they say. In the meantime, the team is also looking for opportunities to treat the neoprene garments of interested users so that they can collect performance data.

MIT Artificial Blubber 02 Web
Holes in a wetsuit reveal the thickness of the neoprene material. The new MIT-developed treatment could provide the same amount of insulation with just half the thickness, the researchers say. Photo, Susan Young.

“Their approach to the problem is a remarkable feat of materials science and also very clever engineering,” says John Dabiri, a professor of civil and environmental engineering and of mechanical engineering at Stanford University, who was not involved in this work. “They’ve managed to achieve something close to an ideal air-like thermal barrier, and they’ve accomplished this using materials that are more compatible with end-uses like scuba diving than previous concepts. The overall performance characteristics could be a game-changer for a variety of applications.”

And Charles Amsler, a professor of biology at the University of Alabama at Birmingham, who has made almost 950 research dives in Antartica but was not connected with this research, says, “It could be very beneficial in cases where flexibility, lack of bulkiness, swimming speed, or reduced drag with diver propulsion vehicles are at a premium, or where environmental hazards make the chance of dive suit puncture high. Normally, diver thermal protection in very cold water is by use of dry suits rather than wetsuits. But wetsuits typically allow much more diver flexibility.”

Amsler adds that “One concern with drysuits is that … should the suit be badly punctured, a diver loses much or all of that insulation. … In a deep or long duration dive where staged decompression would be required to prevent decompression illness (“the bends”), wearing one of these thermally enhanced wetsuits would significantly reduce the chance that a diver with a punctured suit would have to make the choice between potentially fatal hypothermia and potentially debilitating or fatal decompression illness.”

The research team included former MIT postdoc Jeffrey Moran PhD ’17, now at George Mason University; MIT graduate students Anton Cottrill and Zhe Yuan; former postdoc Jesse Benck; and postdoc Pingwei Liu. The work was supported by the U.S. Office of Naval Research, King Abdullah University of Science and Technology, and the U.S Department of Energy.

back to newsletterDavid Chandler | MIT News Office
June 19, 2018

 

Loosely connected disc-shaped “particles” can push and pull one another, moving en masse to transport objects.

Taking a cue from biological cells, researchers from MIT, Columbia University, and elsewhere have developed computationally simple robots that connect in large groups to move around, transport objects, and complete other tasks.

This so-called “particle robotics” system — based on a project by MIT, Columbia Engineering, Cornell University, and Harvard University researchers — comprises many individual disc-shaped units, which the researchers call “particles.” The particles are loosely connected by magnets around their perimeters, and each unit can only do two things: expand and contract. (Each particle is about 6 inches in its contracted state and about 9 inches when expanded.) That motion, when carefully timed, allows the individual particles to push and pull one another in coordinated movement. On-board sensors enable the cluster to gravitate toward light sources.

In a Nature paper published March 20, 2019, the researchers demonstrate a cluster of two dozen real robotic particles and a virtual simulation of up to 100,000 particles moving through obstacles toward a light bulb. They also show that a particle robot can transport objects placed in its midst.

Particle robots can form into many configurations and fluidly navigate around obstacles and squeeze through tight gaps. Notably, none of the particles directly communicate with or rely on one another to function, so particles can be added or subtracted without any impact on the group. In their paper, the researchers show particle robotic systems can complete tasks even when many units malfunction.

The paper represents a new way to think about robots, which are traditionally designed for one purpose, comprise many complex parts, and stop working when any part malfunctions. Robots made up of these simplistic components, the researchers say, could enable more scalable, flexible, and robust systems.

“We have small robot cells that are not so capable as individuals but can accomplish a lot as a group,” says Daniela Rus, director of the Computer Science and Artificial Intelligence Laboratory (CSAIL) and the Andrew and Erna Viterbi Professor of Electrical Engineering and Computer Science. “The robot by itself is static, but when it connects with other robot particles, all of a sudden the robot collective can explore the world and control more complex actions. With these ‘universal cells,’ the robot particles can achieve different shapes, global transformation, global motion, global behavior, and, as we have shown in our experiments, follow gradients of light. This is very powerful.”Joining Rus on the paper are: first author Shuguang Li, a CSAIL postdoc; co-first author Richa Batra and corresponding author Hod Lipson, both of Columbia Engineering; David Brown, Hyun-Dong Chang, and Nikhil Ranganathan of Cornell; and Chuck Hoberman of Harvard.At MIT, Rus has been working on modular, connected robots for nearly 20 years, including an expanding and contracting cube robot that could connect to others to move around. But the square shape limited the robots’ group movement and configurations.

In collaboration with Lipson’s lab, where Li was a postdoc until coming to MIT in 2014, the researchers went for disc-shaped mechanisms that can rotate around one another. They can also connect and disconnect from each other, and form into many configurations.

Each unit of a particle robot has a cylindrical base, which houses a battery, a small motor, sensors that detect light intensity, a microcontroller, and a communication component that sends out and receives signals. Mounted on top is a children’s toy called a Hoberman Flight Ring — its inventor is one of the paper’s co-authors — which consists of small panels connected in a circular formation that can be pulled to expand and pushed back to contract. Two small magnets are installed in each panel.

The trick was programming the robotic particles to expand and contract in an exact sequence to push and pull the whole group toward a destination light source. To do so, the researchers equipped each particle with an algorithm that analyzes broadcasted information about light intensity from every other particle, without the need for direct particle-to-particle communication.

The sensors of a particle detect the intensity of light from a light source; the closer the particle is to the light source, the greater the intensity. Each particle constantly broadcasts a signal that shares its perceived intensity level with all other particles. Say a particle robotic system measures light intensity on a scale of levels 1 to 10: Particles closest to the light register a level 10 and those furthest will register level 1. The intensity level, in turn, corresponds to a specific time that the particle must expand. Particles experiencing the highest intensity — level 10 — expand first. As those particles contract, the next particles in order, level 9, then expand. That timed expanding and contracting motion happens at each subsequent level.

“This creates a mechanical expansion-contraction wave, a coordinated pushing and dragging motion, that moves a big cluster toward or away from environmental stimuli,” Li says. The key component, Li adds, is the precise timing from a shared synchronized clock among the particles that enables movement as efficiently as possible: “If you mess up the synchronized clock, the system will work less efficiently.”

In videos, the researchers demonstrate a particle robotic system comprising real particles moving and changing directions toward different light bulbs as they’re flicked on, and working its way through a gap between obstacles. In their paper, the researchers also show that simulated clusters of up to 10,000 particles maintain locomotion, at half their speed, even with up to 20 percent of units failed.

“It’s a bit like the proverbial ‘gray goo,’” says Lipson, a professor of mechanical engineering at Columbia Engineering, referencing the science-fiction concept of a self-replicating robot that comprises billions of nanobots. “The key novelty here is that you have a new kind of robot that has no centralized control, no single point of failure, no fixed shape, and its components have no unique identity.”

The next step, Lipson adds, is miniaturizing the components to make a robot composed of millions of microscopic particles.

back to newsletter– Rob Matheson | MIT News Office
March 20, 2019

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