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    A home where world-changing innovations take flight

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    In a large, open space on the first floor of 750 Main Street in Cambridge, Massachusetts, a carbon-capture company is heating up molten salts to 600 degrees Celsius right next to a quantum computing company’s device for supercooling qubits. The difference is about 900 degrees across 15 feet.

    It doesn’t take long in the tour of The Engine Accelerator to realize this isn’t your typical co-working space. Companies here are working at the extremes to develop new technologies with world-changing impact — what The Engine Accelerator’s leaders call “tough tech.”

    Comprising four floors and 150,000 square feet next door to MIT’s campus, the new space offers startups specialized lab equipment, advanced machining, fabrication facilities, office space, and a range of startup support services.

    The goal is to give young companies merging science and engineering all of the resources they need to move ideas from the lab bench to their own mass manufacturing lines.

    “The infrastructure has always been a really important accelerant for getting these kinds of companies off and running,” The Engine Accelerator President Emily Knight says. “Now you can start a company and, on day one, start building. Real estate is such a big factor. Our thought was, let’s make this investment in the infrastructure for the founders. It’s an agile lease that enables them to be very flexible as they grow.”

    Since the new facility opened its doors in the summer of 2022, the Accelerator has welcomed around 100 companies that employ close to 1,000 people. In addition to the space, members enjoy educational workshops on topics like fundraising and hiring, events, and networking opportunities that the Accelerator team hopes foster a sense of community among people working in the tough tech space overall.

    “We’re not just advocates for the startups in the space,” Knight says. “We’re advocates for tough tech as a whole. We think it’s important for the state of Massachusetts to create a tough tech hub here, and we think it’s important for national competitiveness.”

    Tough tech gets a home

    The Engine was spun out of MIT in 2016 as a public benefit corporation with the mission of bridging the gap between discovery and commercialization. Since its inception, it has featured an investment component, now known as Engine Ventures, and a shared services component.

    From the moment The Engine opened its doors to startups in its original headquarters on Massachusetts Avenue in Cambridge, the services team got a firsthand look at the unique challenges faced by tough tech startups. After speaking with founders, they realized their converted office space would need more power, stronger floors, and full lab accommodations.

    The team rose to the challenge. They turned a closet into a bio lab. They turned an unused wellness room into a laser lab. They managed to accommodate Commonwealth Fusion Systems when the founders informed them a 5,000-pound magnet would soon arrive for testing.

    But supporting ambitious founders in their quest to build world-changing companies was always going to require a bigger boat. As early as 2017, MIT’s leaders were considering turning the old Polaroid building, which had sat empty next to MIT’s campus for nearly 20 years, into the new home for tough tech.

    Speaking of tough, construction crews began the extensive building renovations for the Accelerator at the end of 2019, a few months before the Covid-19 pandemic. The team managed to avoid the worst of the supply chain disruptions, but they quickly learned the building has its quirks. Each floor is a different ceiling height, and massive pillars known as mushroom columns punctuate each floor.

    Based on conversations with founders, The Engine’s Accelerator team outfitted the renovated building with office and co-working space, a full machine shop, labs for biology and chemistry work, an array of 3D printers, bike storage, and, perhaps most important, cold brew on tap.

    “I think of the Accelerator as a really great Airbnb host rather than a landlord, where maybe you rented a bedroom in a large house, but you feel like you rented the whole thing because you have access to all kinds of amazing equipment,” says Bernardo Cervantes PhD ’20, co-founder of Concerto Biosciences, which is developing microbes for a variety of uses in human health and agriculture.

    The Engine Accelerator’s team credits MIT leadership with helping them manage the project, noting that the MIT Environment, Health and Safety office was particularly helpful.

    A week after the Accelerator opened its doors in August 2022, on a single sweltering day, 35 companies moved in. By 2023, the Accelerator was home to 55 companies. Since then, the Accelerator’s team has done everything they could to continue to grow.

    “At one point, one of our team members came to me with her tail between her legs and sheepishly said, ‘I gave our office space to a startup,’” Knight recalls. “I said, ‘Yes! That means you get it! We don’t need an office — we can sit anywhere.’”

    The first floor holds some of the largest machinery, including that molten salt device (developed by Mantel Capture) and the quantum computer (developed by Atlantic Quantum). On the next level, a machine shop and a fabrication space featuring every 3D printer imaginable offer ways for companies to quickly build prototype products or parts. Another floor is dubbed “the Avenue” and features a kitchen and tables for networking and serendipitous meetings. The Avenue is lined by huge garage doors that open to accommodate larger crowds for workshops and meeting spaces.

    “Even though the founders are working in different spaces, we wanted to create an area where people can connect and run into each other and get help with 3D printing or hiring or anything else,” Knight says. “It fosters those casual interactions that are very important for startups.”

    An ecosystem to change the world

    Only about one-fifth of the companies in the Accelerator space are portfolio companies of Engine Ventures. The two entities operate separately, but they pool their shared learning about supporting tough tech, and Engine Ventures has an office in the Accelerator’s space.

    Engine Ventures CEO Katie Rae sees it as a symbiotic partnership.

    “We needed to have all these robust services for everyone in tough tech, not just the portfolio companies,” Rae says. “We’ll always work together and produce the Tough Tech Summit together because of our overarching missions. It’s very much like a rising tide lifts all boats. All of these companies are working to change the world in their own verticals, so we’re just focusing on the impact they’re trying to have and making that the story.”

    Rae says MIT has helped both of The Engine’s teams think through the best way to support tough tech startups.

    “Being a partner with MIT, which understands innovation and safety better than anyone, has allowed us to say yes to more things and have more flexibility,” Rae says. “If you’re going to go at breakneck speed to solve global problems, you better have a mentality of getting things done fast and safely, and I think that’s been a core tenet of The Engine.”

    Meanwhile, Knight says her team hasn’t stopped learning from the tough tech community and will continue to adapt.

    “There’s just a waterfall of information coming from these companies,” Knight says. “It’s about iterating on our services to best support them, so we can go to people on our team and ask, ‘Can you learn to run this type of program, because we just learned these five founders need it?’ Every founder we know in the area has a badge so they can come in. We want to create a hub for tough tech within this Kendall Square area that’s already a hub in so many ways.” More

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      in Energy

      Cobalt-free batteries could power cars of the future

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      Many electric vehicles are powered by batteries that contain cobalt — a metal that carries high financial, environmental, and social costs.

      MIT researchers have now designed a battery material that could offer a more sustainable way to power electric cars. The new lithium-ion battery includes a cathode based on organic materials, instead of cobalt or nickel (another metal often used in lithium-ion batteries).

      In a new study, the researchers showed that this material, which could be produced at much lower cost than cobalt-containing batteries, can conduct electricity at similar rates as cobalt batteries. The new battery also has comparable storage capacity and can be charged up faster than cobalt batteries, the researchers report.

      “I think this material could have a big impact because it works really well,” says Mircea Dincă, the W.M. Keck Professor of Energy at MIT. “It is already competitive with incumbent technologies, and it can save a lot of the cost and pain and environmental issues related to mining the metals that currently go into batteries.”

      Dincă is the senior author of the study, which appears today in the journal ACS Central Science. Tianyang Chen PhD ’23 and Harish Banda, a former MIT postdoc, are the lead authors of the paper. Other authors include Jiande Wang, an MIT postdoc; Julius Oppenheim, an MIT graduate student; and Alessandro Franceschi, a research fellow at the University of Bologna.

      Alternatives to cobalt

      Most electric cars are powered by lithium-ion batteries, a type of battery that is recharged when lithium ions flow from a positively charged electrode, called a cathode, to a negatively electrode, called an anode. In most lithium-ion batteries, the cathode contains cobalt, a metal that offers high stability and energy density.

      However, cobalt has significant downsides. A scarce metal, its price can fluctuate dramatically, and much of the world’s cobalt deposits are located in politically unstable countries. Cobalt extraction creates hazardous working conditions and generates toxic waste that contaminates land, air, and water surrounding the mines.

      “Cobalt batteries can store a lot of energy, and they have all of features that people care about in terms of performance, but they have the issue of not being widely available, and the cost fluctuates broadly with commodity prices. And, as you transition to a much higher proportion of electrified vehicles in the consumer market, it’s certainly going to get more expensive,” Dincă says.

      Because of the many drawbacks to cobalt, a great deal of research has gone into trying to develop alternative battery materials. One such material is lithium-iron-phosphate (LFP), which some car manufacturers are beginning to use in electric vehicles. Although still practically useful, LFP has only about half the energy density of cobalt and nickel batteries.

      Another appealing option are organic materials, but so far most of these materials have not been able to match the conductivity, storage capacity, and lifetime of cobalt-containing batteries. Because of their low conductivity, such materials typically need to be mixed with binders such as polymers, which help them maintain a conductive network. These binders, which make up at least 50 percent of the overall material, bring down the battery’s storage capacity.

      About six years ago, Dincă’s lab began working on a project, funded by Lamborghini, to develop an organic battery that could be used to power electric cars. While working on porous materials that were partly organic and partly inorganic, Dincă and his students realized that a fully organic material they had made appeared that it might be a strong conductor.

      This material consists of many layers of TAQ (bis-tetraaminobenzoquinone), an organic small molecule that contains three fused hexagonal rings. These layers can extend outward in every direction, forming a structure similar to graphite. Within the molecules are chemical groups called quinones, which are the electron reservoirs, and amines, which help the material to form strong hydrogen bonds.

      Those hydrogen bonds make the material highly stable and also very insoluble. That insolubility is important because it prevents the material from dissolving into the battery electrolyte, as some organic battery materials do, thereby extending its lifetime.

      “One of the main methods of degradation for organic materials is that they simply dissolve into the battery electrolyte and cross over to the other side of the battery, essentially creating a short circuit. If you make the material completely insoluble, that process doesn’t happen, so we can go to over 2,000 charge cycles with minimal degradation,” Dincă says.

      Strong performance

      Tests of this material showed that its conductivity and storage capacity were comparable to that of traditional cobalt-containing batteries. Also, batteries with a TAQ cathode can be charged and discharged faster than existing batteries, which could speed up the charging rate for electric vehicles.

      To stabilize the organic material and increase its ability to adhere to the battery’s current collector, which is made of copper or aluminum, the researchers added filler materials such as cellulose and rubber. These fillers make up less than one-tenth of the overall cathode composite, so they don’t significantly reduce the battery’s storage capacity.

      These fillers also extend the lifetime of the battery cathode by preventing it from cracking when lithium ions flow into the cathode as the battery charges.

      The primary materials needed to manufacture this type of cathode are a quinone precursor and an amine precursor, which are already commercially available and produced in large quantities as commodity chemicals. The researchers estimate that the material cost of assembling these organic batteries could be about one-third to one-half the cost of cobalt batteries.

      Lamborghini has licensed the patent on the technology. Dincă’s lab plans to continue developing alternative battery materials and is exploring possible replacement of lithium with sodium or magnesium, which are cheaper and more abundant than lithium. More

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      in Energy

      The future of motorcycles could be hydrogen

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      MIT’s Electric Vehicle Team, which has a long record of building and racing innovative electric vehicles, including cars and motorcycles, in international professional-level competitions, is trying something very different this year: The team is building a hydrogen-powered electric motorcycle, using a fuel cell system, as a testbed for new hydrogen-based transportation.

      The motorcycle successfully underwent its first full test-track demonstration in October. It is designed as an open-source platform that should make it possible to swap out and test a variety of different components, and for others to try their own versions based on plans the team is making freely available online.

      Aditya Mehrotra, who is spearheading the project, is a graduate student working with mechanical engineering professor Alex Slocum, the Walter M. May  and A. Hazel May Chair in Emerging Technologies. Mehrotra was studying energy systems and happened to also really like motorcycles, he says, “so we came up with the idea of a hydrogen-powered bike. We did an evaluation study, and we thought that this could actually work. We [decided to] try to build it.”

      Team members say that while battery-powered cars are a boon for the environment, they still face limitations in range and have issues associated with the mining of lithium and resulting emissions. So, the team was interested in exploring hydrogen-powered vehicles as a clean alternative, allowing for vehicles that could be quickly refilled just like gasoline-powered vehicles.

      Unlike past projects by the team, which has been part of MIT since 2005, this vehicle will not be entering races or competitions but will be presented at a variety of conferences. The team, consisting of about a dozen students, has been working on building the prototype since January 2023. In October they presented the bike at the Hydrogen Americas Summit, and in May they will travel to the Netherlands to present it at the World Hydrogen Summit. In addition to the two hydrogen summits, the team plans to show its bike at the Consumer Electronics Show in Las Vegas this month.

      “We’re hoping to use this project as a chance to start conversations around ‘small hydrogen’ systems that could increase demand, which could lead to the development of more infrastructure,” Mehrotra says. “We hope the project can help find new and creative applications for hydrogen.” In addition to these demonstrations and the online information the team will provide, he adds, they are also working toward publishing papers in academic journals describing their project and lessons learned from it, in hopes of making “an impact on the energy industry.”

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      For the love of speed: Building a hydrogen-powered motorcycle

      The motorcycle took shape over the course of the year piece by piece. “We got a couple of industry sponsors to donate components like the fuel cell and a lot of the major components of the system,” he says. They also received support from the MIT Energy Initiative, the departments of Mechanical Engineering and Electrical Engineering and Computer Science, and the MIT Edgerton Center.

      Initial tests were conducted on a dynamometer, a kind of instrumented treadmill Mehrotra describes as “basically a mock road.” The vehicle used battery power during its development, until the fuel cell, provided by South Korean company Doosan, could be delivered and installed. The space the group has used to design and build the prototype, the home of the Electric Vehicle Team, is in MIT’s Building N51 and is well set up to do detailed testing of each of the bike’s components as it is developed and integrated.

      Elizabeth Brennan, a senior in mechanical engineering, says she joined the team in January 2023 because she wanted to gain more electrical engineering experience, “and I really fell in love with it.” She says group members “really care and are very excited to be here and work on this bike and believe in the project.”

      Brennan, who is the team’s safety lead, has been learning about the safe handling methods required for the bike’s hydrogen fuel, including the special tanks and connectors needed. The team initially used a commercially available electric motor for the prototype but is now working on an improved version, designed from scratch, she says, “which gives us a lot more flexibility.”

      As part of the project, team members are developing a kind of textbook describing what they did and how they carried out each step in the process of designing and fabricating this hydrogen electric fuel-cell bike. No such motorcycle yet exists as a commercial product, though a few prototypes have been built.

      That kind of guidebook to the process “just doesn’t exist,” Brennan says. She adds that “a lot of the technology development for hydrogen is either done in simulation or is still in the prototype stages, because developing it is expensive, and it’s difficult to test these kinds of systems.” One of the team’s goals for the project is to make everything available as an open-source design, and “we want to provide this bike as a platform for researchers and for education, where researchers can test ideas in both space- and funding-constrained environments.”

      Unlike a design built as a commercial product, Mehrotra says, “our vehicle is fully designed for research, so you can swap components in and out, and get real hardware data on how good your designs are.” That can help people work on implementing their new design ideas and help push the industry forward, he says.

      The few prototypes developed previously by some companies were inefficient and expensive, he says. “So far as we know, we are the first fully open-source, rigorously documented, tested and released-as-a-platform, [fuel cell] motorcycle in the world. No one else has made a motorcycle and tested it to the level that we have, and documented to the point that someone might actually be able to take this and scale it in the future, or use it in research.”

      He adds that “at the moment, this vehicle is affordable for research, but it’s not affordable yet for commercial production because the fuel cell is a very big, expensive component.” Doosan Fuel Cell, which provided the fuel cell for the prototype bike, produces relatively small and lightweight fuel cells mostly for use in drones. The company also produces hydrogen storage and delivery systems.

      The project will continue to evolve, says team member Annika Marschner, a sophomore in mechanical engineering. “It’s sort of an ongoing thing, and as we develop it and make changes, make it a stronger, better bike, it will just continue to grow over the years, hopefully,” she says.

      While the Electric Vehicle Team has until now focused on battery-powered vehicles, Marschner says, “Right now we’re looking at hydrogen because it seems like something that’s been less explored than other technologies for making sustainable transportation. So, it seemed like an exciting thing for us to offer our time and effort to.”

      Making it all work has been a long process. The team is using a frame from a 1999 motorcycle, with many custom-made parts added to support the electric motor, the hydrogen tank, the fuel cell, and the drive train. “Making everything fit in the frame of the bike is definitely something we’ve had to think about a lot because there’s such limited space there. So, it required trying to figure out how to mount things in clever ways so that there are not conflicts,” she says.

      Marschner says, “A lot of people don’t really imagine hydrogen energy being something that’s out there being used on the roads, but the technology does exist.” She points out that Toyota and Hyundai have hydrogen-fueled vehicles on the market, and that some hydrogen fuel stations exist, mostly in California, Japan, and some European countries. But getting access to hydrogen, “for your average consumer on the East Coast, is a huge, huge challenge. Infrastructure is definitely the biggest challenge right now to hydrogen vehicles,” she says.

      She sees a bright future for hydrogen as a clean fuel to replace fossil fuels over time. “I think it has a huge amount of potential,” she says. “I think one of the biggest challenges with moving hydrogen energy forward is getting these demonstration projects actually developed and showing that these things can work and that they can work well. So, we’re really excited to bring it along further.” More

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      in Security

      A new way to swiftly eliminate micropollutants from water

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      “Zwitterionic” might not be a word you come across every day, but for Professor Patrick Doyle of the MIT Department of Chemical Engineering, it’s a word that’s central to the technology his group is developing to remove micropollutants from water. Derived from the German word “zwitter,” meaning “hybrid,” “zwitterionic” molecules are those with an equal number of positive and negative charges.

      Devashish Gokhale, a PhD student in Doyle’s lab, uses the example of a magnet to describe zwitterionic materials. “On a magnet, you have a north pole and a south pole that stick to each other, and on a zwitterionic molecule, you have a positive charge and a negative charge which stick to each other in a similar way.” Because many inorganic micropollutants and some organic micropollutants are themselves charged, Doyle and his team have been investigating how to deploy zwitterionic molecules to capture micropollutants in water. 

      In a new paper in Nature Water, Doyle, Gokhale, and undergraduate student Andre Hamelberg explain how they use zwitterionic hydrogels to sustainably capture both organic and inorganic micropollutants from water with minimal operational complexity. In the past, zwitterionic molecules have been used as coatings on membranes for water treatment because of their non-fouling properties. But in the Doyle group’s system, zwitterionic molecules are used to form the scaffold material, or backbone within the hydrogel — a porous three-dimensional network of polymer chains that contains a significant amount of water. “Zwitterionic molecules have very strong attraction to water compared to other materials which are used to make hydrogels or polymers,” says Gokhale. What’s more, the positive and negative charges on zwitterionic molecules cause the hydrogels to have lower compressibility than what has been commonly observed in hydrogels. This makes for significantly more swollen, robust, and porous hydrogels, which is important for the scale up of the hydrogel-based system for water treatment.

      The early stages of this research were supported by a seed grant from MIT’s Abdul Latif Jameel Water and Food Systems Lab (J-WAFS). Doyle’s group is now pursuing commercialization of the platform for both at-home use and industrial scale applications, with support from a J-WAFS Solutions grant.

      Seeking a sustainable solution

      Micropollutants are chemically diverse materials that can be harmful to human health and the environment, even though they are typically found at low concentrations (micrograms to milligrams per liter) relative to conventional contaminants. Micropollutants can be organic or inorganic and can be naturally-occurring or synthetic. Organic micropollutants are mostly carbon-based molecules and include pesticides and per- and polyfluoroalkyl substances (PFAS), known as “forever chemicals.” Inorganic micropollutants, such as heavy metals like lead and arsenic, tend to be smaller than organic micropollutants. Unfortunately, both organic and inorganic micropollutants are pervasive in the environment.

      Many micropollutants come from industrial processes, but the effects of human-induced climate change are also contributing to the environmental spread of micropollutants. Gokhale explains that, in California, for example, fires burn plastic electrical cables and leech micropollutants into natural ecosystems. Doyle adds that “outside of climate change, things like pandemics can spike the number of organic micropollutants in the environment due to high concentrations of pharmaceuticals in wastewater.”

      It’s no surprise then, that over the past few years micropollutants have become more and more of a concern. These chemicals have garnered attention in the media and led to “significant change in the environmental engineering and regulatory landscape” says Gokhale. In March 2023, the U.S. Environmental Protection Agency (EPA) proposed a strict, federal standard that would regulate six different PFAS chemicals in drinking water. Just last October, the EPA proposed banning the micropollutant trichloroethylene, a cancer-causing chemical that can be found in brake cleaners and other consumer products. And as recently as November, the EPA proposed that water utilities nationwide be required to replace all of their lead pipes to protect the public from lead exposure. Internationally, Gokhale notes the Oslo Paris Convention, whose mission is to protect the marine environment of the northeast Atlantic Ocean, including phasing out the discharge of offshore chemicals from the oil and gas industries. 

      With each new, necessary regulation to protect the safety of our water resources, the need for effective water treatment processes grows. Compounding this challenge is the need to make water treatment processes that are sustainable and energy-efficient. 

      The benchmark method to treat micropollutants in water is activated carbon. However, making filters with activated carbon is energy-intensive, requiring very high temperatures in large, centralized facilities. Gokhale says approximately “four kilograms of coal are needed to make one kilogram of activated carbon, so you lose a significant amount of carbon dioxide to the environment.” According to the World Economic Forum, global water and wastewater treatment accounts for 5 percent of annual emissions. In the U.S. alone, the EPA reports that drinking water and wastewater systems account for over 45 million tons of greenhouse gas emissions annually.

      “We need to develop methods which have smaller climate footprints than methods which are being used industrially today,” says Gokhale.

      Supporting a “high-risk” project

      In September 2019, Doyle and his lab embarked on an initial project to develop a microparticle-based platform to remove a broad range of micropollutants from water. Doyle’s group had been using hydrogels in pharmaceutical processing to formulate drug molecules into pill format. When he learned about the J-WAFS seed grant opportunity for early-stage research in water and food systems, Doyle realized his pharmaceutical work with hydrogels could be applied to environmental issues like water treatment. “I would never have gotten funding for this project if I went to the NSF [National Science Foundation], because they would just say, ‘you’re not a water person.’ But the J-WAFS seed grant offered a way for a high-risk, high-reward kind of project,” Doyle says.

      In March 2022, Doyle, Gokhale, and MIT undergraduate Ian Chen published findings from the seed grant work, describing their use of micelles within hydrogels for water treatment. Micelles are spherical structures that form when molecules called surfactants (found in things like soap), come in contact with water or other liquids. The team was able to synthesize micelle-laden hydrogel particles that soak up micropollutants from water like a sponge. Unlike activated carbon, the hydrogel particle system is made from environmentally friendly materials. Furthermore, the system’s materials are made at room temperature, making them exceedingly more sustainable than activated carbon.

      Building off the success of the seed grant, Doyle and his team were awarded a J-WAFS Solutions grant in September 2022 to help move their technology from the lab to the market. With this support, the researchers have been able to build, test, and refine pilot-scale prototypes of their hydrogel platform. System iterations during the solutions grant period have included the use of the zwitterionic molecules, a novel advancement from the seed grant work.  

      Rapid elimination of micropollutants is of special importance in commercial water treatment processes, where there is a limited amount of time water can spend inside the operational filtration unit. This is referred to as contact time, explains Gokhale. In municipal-scale or industrial-scale water treatment systems, contact times are usually less than 20 minutes and can be as short as five minutes. 

      “But as people have been trying to target these emerging micropollutants of concern, they realized they can’t get to sufficiently low concentrations on the same time scales as conventional contaminants,” Gokhale says. “Most technologies focus only on specific molecules or specific classes of molecules. So, you have whole technologies which are focusing only on PFAS, and then you have other technologies for lead and metals. When you start thinking about removing all of these contaminants from water, you end up with designs which have a very large number of unit operations. And that’s an issue because you have plants which are in the middle of large cities, and they don’t necessarily have space to expand to increase their contact times to efficiently remove multiple micropollutants,” he adds.

      Since zwitterionic molecules possess unique properties that confer high porosity, the researchers have been able to engineer a system for quicker uptake of micropollutants from water. Tests show that the hydrogels can eliminate six chemically diverse micropollutants at least 10 times faster than commercial activated carbon. The system is also compatible with a diverse set of materials, making it multifunctional. Micropollutants can bind to many different sites within the hydrogel platform: organic micropollutants bind to the micelles or surfactants while inorganic micropollutants bind to the zwitterionic molecules. Micelles, surfactants, zwitterionic molecules, and other chelating agents can be swapped in and out to essentially tune the system with different functionalities based on the profile of the water being treated. This kind of “plug-and-play” addition of various functional agents does not require a change in the design or synthesis of the hydrogel platform, and adding more functionalities does not take away from existing functionality. In this way, the zwitterionic-based system can rapidly remove multiple contaminants at lower concentrations in a single step, without the need for large, industrial units or capital expenditure. 

      Perhaps most importantly, the particles in the Doyle group’s system can be regenerated and used over and over again. By simply soaking the particles in an ethanol bath, they can be washed of micropollutants for indefinite use without loss of efficacy. When activated carbon is used for water treatment, the activated carbon itself becomes contaminated with micropollutants and must be treated as toxic chemical waste and disposed of in special landfills. Over time, micropollutants in landfills will reenter the ecosystem, perpetuating the problem.

      Arjav Shah, a PhD-MBA candidate in MIT’s Department of Chemical Engineering and the MIT Sloan School of Management, respectively, recently joined the team to lead commercialization efforts. The team has found that the zwitterionic hydrogels could be used in several real-world contexts, ranging from large-scale industrial packed beds to small-scale, portable, off-grid applications — for example, in tablets that could clean water in a canteen — and they have begun piloting the technology through a number of commercialization programs at MIT and in the greater Boston area.

      The combined strengths of each member of the team continue to drive the project forward in impactful ways, including undergraduate students like Andre Hamelberg, the third author on the Nature Water paper. Hamelberg is a participant in MIT’s Undergraduate Research Opportunities Program (UROP). Gokhale, who is also a J-WAFS Fellow, provides training and mentorship to Hamelberg and other UROP students in the lab.

      “We see this as an educational opportunity,” says Gokhale, noting that the UROP students learn science and chemical engineering through the research they conduct in the lab. The J-WAFS project has also been “a way of getting undergrads interested in water treatment and the more sustainable aspects of chemical engineering,” Gokhale says. He adds that it’s “one of the few projects which goes all the way from designing specific chemistries to building small filters and units and scaling them up and commercializing them. It’s a really good learning opportunity for the undergrads and we’re always excited to have them work with us.”

      In four years, the technology has been able to grow from an initial idea to a technology with scalable, real-world applications, making it an exemplar J-WAFS project. The fruitful collaboration between J-WAFS and the Doyle lab serves as inspiration for any MIT faculty who may want to apply their research to water or food systems projects.

      “The J-WAFS project serves as a way to demystify what a chemical engineer does,” says Doyle. “I think that there’s an old idea of chemical engineering as working in just oil and gas. But modern chemical engineering is focused on things which make life and the environment better.” More

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      in Environment

      Harnessing hydrogen’s potential to address long-haul trucking emissions

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      The transportation of goods forms the basis of today’s globally distributed supply chains, and long-haul trucking is a central and critical link in this complex system. To meet climate goals around the world, it is necessary to develop decarbonized solutions to replace diesel powertrains, but given trucking’s indispensable and vast role, these solutions must be both economically viable and practical to implement. While hydrogen-based options, as an alternative to diesel, have the potential to become a promising decarbonization strategy, hydrogen has significant limitations when it comes to delivery and refueling.These roadblocks, combined with hydrogen’s compelling decarbonization potential, are what motivated a team of MIT researchers led by William H. Green, the Hoyt Hottel Professor in Chemical Engineering, to explore a cost-effective way to transport and store hydrogen using liquid organic hydrogen carriers (LOHCs). The team is developing a disruptive technology that allows LOHCs to not only deliver the hydrogen to the trucks, but also store the hydrogen onboard.Their findings were recently published in Energy and Fuels, a peer-reviewed journal of the American Chemical Society, in a paper titled “Perspective on Decarbonizing Long-Haul Trucks Using Onboard Dehydrogenation of Liquid Organic Hydrogen Carriers.” The MIT team is led by Green, and includes graduate students Sayandeep Biswas and Kariana Moreno Sader. Their research is supported by the MIT Climate and Sustainability Consortium (MCSC) through its Seed Awards program and MathWorks, and ties into the work within the MCSC’s Tough Transportation Modes focus area.An “onboard” approachCurrently, LOHCs, which work within existing retail fuel distribution infrastructure, are used to deliver hydrogen gas to refueling stations, where it is then compressed and delivered onto trucks equipped with hydrogen fuel cell or combustion engines.“This current approach incurs significant energy loss due to endothermic hydrogen release and compression at the retail station” says Green. “To address this, our work is exploring a more efficient application, with LOHC-powered trucks featuring onboard dehydrogenation.”To implement such a design, the team aims to modify the truck’s powertrain (the system inside a vehicle that produces the energy to propel it forward) to allow onboard hydrogen release from the LOHCs, using waste heat from the engine exhaust to power the “dehydrogenation” process. 

      Proposed process flow diagram for onboard dehydrogenation. Component sizes are not to scale and have been enlarged for illustrative purposes.

      Image courtesy of the Green Group.

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      The dehydrogenation process happens within a high-temperature reactor, which continually receives hydrogen-rich LOHCs from the fuel storage tank. Hydrogen released from the reactor is fed to the engine, after passing through a separator to remove any lingering LOHC. On its way to the engine, some of the hydrogen gets diverted to a burner to heat the reactor, which helps to augment the reactor heating provided by the engine exhaust gases.Acknowledging and addressing hydrogen’s drawbacksThe team’s paper underscores that current uses of hydrogen, including LOHC systems, to decarbonize the trucking sector have drawbacks. Regardless of technical improvements, these existing options remain prohibitively expensive due to the high cost of retail hydrogen delivery.“We present an alternative option that addresses a lot of the challenges and seems to be a viable way in which hydrogen can be used in this transportation context,” says Biswas, who was recently elected to the MIT Martin Family Society of Fellows for Sustainability for his work in this area. “Hydrogen, when used through LOHCs, has clear benefits for long-hauling, such as scalability and fast refueling time. There is also an enormous potential to improve delivery and refueling to further reduce cost, and our system is working to do that.”“Utilizing hydrogen is an option that is globally accessible, and could be extended to countries like the one where I am from,” says Moreno Sader, who is originally from Colombia. “Since it synergizes with existing infrastructure, large upfront investments are not necessary. The global applicability is huge.”Moreno Sader is a MathWorks Fellow, and, along with the rest of the team, has been using MATLAB tools to develop models and simulations for this work.Different sectors coming togetherDecarbonizing transportation modes, including long-haul trucking, requires expertise and perspectives from different industries — an approach that resonates with the MCSC’s mission.The team’s groundbreaking research into LOHC-powered trucking is among several projects supported by the MCSC within its Tough Transportation Modes focus area, led by postdoc Impact Fellow Danika MacDonell. The MCSC-supported projects were chosen to tackle a complementary set of societally important and industry-relevant challenges to decarbonizing heavy-duty transportation, which span a range of sectors and solution pathways. Other projects focus, for example, on logistics optimization for electrified trucking fleets, or air quality and climate impacts of ammonia-powered shipping.The MCSC works to support and amplify the impact of these projects by engaging the research teams with industry partners from a variety of sectors. In addition, the MCSC pursues a collective multisectoral approach to decarbonizing transportation by facilitating shared learning across the different projects through regular cross-team discussion.The research led by Green celebrates this cross-sector theme by integrating industry-leading computing tools provided by MathWorks with cutting-edge developments in chemical engineering, as well as industry-leading commercial LOHC reactor demonstrations, to build a compelling vision for cost-effective LOHC-powered trucking.The review and research conducted in the Energy and Fuels article lays the groundwork for further investigations into LOHC-powered truck design. The development of such a vehicle — with a power-dense, efficient, and robust onboard hydrogen release system — requires dedicated investigations and further optimization of core components geared specifically toward the trucking application. More

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      in Energy

      Making aviation fuel from biomass

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      In 2021, nearly a quarter of the world’s carbon dioxide emissions came from the transportation sector, with aviation being a significant contributor. While the growing use of electric vehicles is helping to clean up ground transportation, today’s batteries can’t compete with fossil fuel-derived liquid hydrocarbons in terms of energy delivered per pound of weight — a major concern when it comes to flying. Meanwhile, based on projected growth in travel demand, consumption of jet fuel is projected to double between now and 2050 — the year by which the international aviation industry has pledged to be carbon neutral.

      Many groups have targeted a 100 percent sustainable hydrocarbon fuel for aircraft, but without much success. Part of the challenge is that aviation fuels are so tightly regulated. “This is a subclass of fuels that has very specific requirements in terms of the chemistry and the physical properties of the fuel, because you can’t risk something going wrong in an airplane engine,” says Yuriy Román-Leshkov, the Robert T. Haslam Professor of Chemical Engineering. “If you’re flying at 30,000 feet, it’s very cold outside, and you don’t want the fuel to thicken or freeze. That’s why the formulation is very specific.”

      Aviation fuel is a combination of two large classes of chemical compounds. Some 75 to 90 percent of it is made up of “aliphatic” molecules, which consist of long chains of carbon atoms linked together. “This is similar to what we would find in diesel fuels, so it’s a classic hydrocarbon that is out there,” explains Román-Leshkov. The remaining 10 to 25 percent consists of “aromatic” molecules, each of which includes at least one ring made up of six connected carbon atoms.

      In most transportation fuels, aromatic hydrocarbons are viewed as a source of pollution, so they’re removed as much as possible. However, in aviation fuels, some aromatic molecules must remain because they set the necessary physical and combustion properties of the overall mixture. They also perform one more critical task: They ensure that seals between various components in the aircraft’s fuel system are tight. “The aromatics get absorbed by the plastic seals and make them swell,” explains Román-Leshkov. “If for some reason the fuel changes, so can the seals, and that’s very dangerous.”

      As a result, aromatics are a necessary component — but they’re also a stumbling block in the move to create sustainable aviation fuels, or SAFs. Companies know how to make the aliphatic fraction from inedible parts of plants and other renewables, but they haven’t yet developed an approved method of generating the aromatic fraction from sustainable sources. As a result, there’s a “blending wall,” explains Román-Leshkov. “Since we need that aromatic content — regardless of its source — there will always be a limit on how much of the sustainable aliphatic hydrocarbons we can use without changing the properties of the mixture.” He notes a similar blending wall with gasoline. “We have a lot of ethanol, but we can’t add more than 10 percent without changing the properties of the gasoline. In fact, current engines can’t handle even 15 percent ethanol without modification.”

      No shortage of renewable source material — or attempts to convert it

      For the past five years, understanding and solving the SAF problem has been the goal of research by Román-Leshkov and his MIT team — Michael L. Stone PhD ’21, Matthew S. Webber, and others — as well as their collaborators at Washington State University, the National Renewable Energy Laboratory (NREL), and the Pacific Northwest National Laboratory. Their work has focused on lignin, a tough material that gives plants structural support and protection against microbes and fungi. About 30 percent of the carbon in biomass is in lignin, yet when ethanol is generated from biomass, the lignin is left behind as a waste product.

      Despite valiant efforts, no one has found an economically viable, scalable way to turn lignin into useful products, including the aromatic molecules needed to make jet fuel 100 percent sustainable. Why not? As Román-Leshkov says, “It’s because of its chemical recalcitrance.” It’s difficult to make it chemically react in useful ways. As a result, every year millions of tons of waste lignin are burned as a low-grade fuel, used as fertilizer, or simply thrown away.

      Understanding the problem requires understanding what’s happening at the atomic level. A single lignin molecule — the starting point of the challenge — is a big “macromolecule” made up of a network of many aromatic rings connected by oxygen and hydrogen atoms. Put simply, the key to converting lignin into the aromatic fraction of SAF is to break that macromolecule into smaller pieces while in the process getting rid of all of the oxygen atoms.

      In general, most industrial processes begin with a chemical reaction that prevents the subsequent upgrading of lignin: As the lignin is extracted from the biomass, the aromatic molecules in it react with one another, linking together to form strong networks that won’t react further. As a result, the lignin is no longer useful for making aviation fuels.

      To avoid that outcome, Román-Leshkov and his team utilize another approach: They use a catalyst to induce a chemical reaction that wouldn’t normally occur during extraction. By reacting the biomass in the presence of a ruthenium-based catalyst, they are able to remove the lignin from the biomass and produce a black liquid called lignin oil. That product is chemically stable, meaning that the aromatic molecules in it will no longer react with one another.

      So the researchers have now successfully broken the original lignin macromolecule into fragments that contain just one or two aromatic rings each. However, while the isolated fragments don’t chemically react, they still contain oxygen atoms. Therefore, one task remains: finding a way to remove the oxygen atoms.

      In fact, says Román-Leshkov, getting from the molecules in the lignin oil to the targeted aromatic molecules required them to accomplish three things in a single step: They needed to selectively break the carbon-oxygen bonds to free the oxygen atoms; they needed to avoid incorporating noncarbon atoms into the aromatic rings (for example, atoms from the hydrogen gas that must be present for all of the chemical transformations to occur); and they needed to preserve the carbon backbone of the molecule — that is, the series of linked carbon atoms that connect the aromatic rings that remain.

      Ultimately, Román-Leshkov and his team found a special ingredient that would do the trick: a molybdenum carbide catalyst. “It’s actually a really amazing catalyst because it can perform those three actions very well,” says Román-Leshkov. “In addition to that, it’s extremely resistant to poisons. Plants can contain a lot of components like proteins, salts, and sulfur, which often poison catalysts so they don’t work anymore. But molybdenum carbide is very robust and isn’t strongly influenced by such impurities.”

      Trying it out on lignin from poplar trees

      To test their approach in the lab, the researchers first designed and built a specialized “trickle-bed” reactor, a type of chemical reactor in which both liquids and gases flow downward through a packed bed of catalyst particles. They then obtained biomass from a poplar, a type of tree known as an “energy crop” because it grows quickly and doesn’t require a lot of fertilizer.

      To begin, they reacted the poplar biomass in the presence of their ruthenium-based catalyst to extract the lignin and produce the lignin oil. They then flowed the oil through their trickle-bed reactor containing the molybdenum carbide catalyst. The mixture that formed contained some of the targeted product but also a lot of others that still contained oxygen atoms.

      Román-Leshkov notes that in a trickle-bed reactor, the time during which the lignin oil is exposed to the catalyst depends entirely on how quickly it drips down through the packed bed. To increase the exposure time, they tried passing the oil through the same catalyst twice. However, the distribution of products that formed in the second pass wasn’t as they had predicted based on the outcome of the first pass.

      With further investigation, they figured out why. The first time the lignin oil drips through the reactor, it deposits oxygen onto the catalyst. The deposition of the oxygen changes the behavior of the catalyst such that certain products appear or disappear — with the temperature being critical. “The temperature and oxygen content set the condition of the catalyst in the first pass,” says Román-Leshkov. “Then, on the second pass, the oxygen content in the flow is lower, and the catalyst can fully break the remaining carbon-oxygen bonds.” The process can thus operate continuously: Two separate reactors containing independent catalyst beds would be connected in series, with the first pretreating the lignin oil and the second removing any oxygen that remains.

      Based on a series of experiments involving lignin oil from poplar biomass, the researchers determined the operating conditions yielding the best outcome: 350 degrees Celsius in the first step and 375 C in the second step. Under those optimized conditions, the mixture that forms is dominated by the targeted aromatic products, with the remainder consisting of small amounts of other jet-fuel aliphatic molecules and some remaining oxygen-containing molecules. The catalyst remains stable while generating more than 87 percent (by weight) of aromatic molecules.

      “When we do our chemistry with the molybdenum carbide catalyst, our total carbon yields are nearly 85 percent of the theoretical carbon yield,” says Román-Leshkov. “In most lignin-conversion processes, the carbon yields are very low, on the order of 10 percent. That’s why the catalysis community got very excited about our results — because people had not seen carbon yields as high as the ones we generated with this catalyst.”

      There remains one key question: Does the mixture of components that forms have the properties required for aviation fuel? “When we work with these new substrates to make new fuels, the blend that we create is different from standard jet fuel,” says Román-Leshkov. “Unless it has the exact properties required, it will not qualify for certification as jet fuel.”

      To check their products, Román-Leshkov and his team send samples to Washington State University, where a team operates a combustion lab devoted to testing fuels. Results from initial testing of the composition and properties of the samples have been encouraging. Based on the composition and published prescreening tools and procedures, the researchers have made initial property predictions for their samples, and they looked good. For example, the freezing point, viscosity, and threshold sooting index are predicted to be lower than the values for conventional aviation aromatics. (In other words, their material should flow more easily and be less likely to freeze than conventional aromatics while also generating less soot in the atmosphere when they burn.) Overall, the predicted properties are near to or more favorable than those of conventional fuel aromatics.

      Next steps

      The researchers are continuing to study how their sample blends behave at different temperatures and, in particular, how well they perform that key task: soaking into and swelling the seals inside jet engines. “These molecules are not the typical aromatic molecules that you use in jet fuel,” says Román-Leshkov. “Preliminary tests with sample seals show that there’s no difference in how our lignin-derived aromatics swell the seals, but we need to confirm that. There’s no room for error.”

      In addition, he and his team are working with their NREL collaborators to scale up their methods. NREL has much larger reactors and other infrastructure needed to produce large quantities of the new sustainable blend. Based on the promising results thus far, the team wants to be prepared for the further testing required for the certification of jet fuels. In addition to testing samples of the fuel, the full certification procedure calls for demonstrating its behavior in an operating engine — “not while flying, but in a lab,” clarifies Román-Leshkov. In addition to requiring large samples, that demonstration is both time-consuming and expensive — which is why it’s the very last step in the strict testing required for a new sustainable aviation fuel to be approved.

      Román-Leshkov and his colleagues are now exploring the use of their approach with other types of biomass, including pine, switchgrass, and corn stover (the leaves, stalks, and cobs left after corn is harvested). But their results with poplar biomass are promising. If further testing confirms that their aromatic products can replace the aromatics now in jet fuel, “the blending wall could disappear,” says Román-Leshkov. “We’ll have a means of producing all the components in aviation fuel from renewable material, potentially leading to aircraft fuel that’s 100 percent sustainable.”

      This research was initially funded by the Center for Bioenergy Innovation, a U.S. Department of Energy (DOE) Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. More recent funding came from the DOE Bioenergy Technologies Office and from Eni S.p.A. through the MIT Energy Initiative. Michael L. Stone PhD ’21 is now a postdoc in chemical engineering at Stanford University. Matthew S. Webber is a graduate student in the Román-Leshkov group, now on leave for an internship at the National Renewable Energy Laboratory.

      This article appears in the Spring 2023 issue of Energy Futures, the magazine of the MIT Energy Initiative. More

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      in Energy

      Simple superconducting device could dramatically cut energy use in computing, other applications

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      MIT scientists and their colleagues have created a simple superconducting device that could transfer current through electronic devices much more efficiently than is possible today. As a result, the new diode, a kind of switch, could dramatically cut the amount of energy used in high-power computing systems, a major problem that is estimated to become much worse. Even though it is in the early stages of development, the diode is more than twice as efficient as similar ones reported by others. It could even be integral to emerging quantum computing technologies.

      The work, which is reported in the July 13 online issue of Physical Review Letters, is also the subject of a news story in Physics Magazine.

      “This paper showcases that the superconducting diode is an entirely solved problem from an engineering perspective,” says Philip Moll, director of the Max Planck Institute for the Structure and Dynamics of Matter in Germany. Moll was not involved in the work. “The beauty of [this] work is that [Moodera and colleagues] obtained record efficiencies without even trying [and] their structures are far from optimized yet.”

      “Our engineering of a superconducting diode effect that is robust and can operate over a wide temperature range in simple systems can potentially open the door for novel technologies,” says Jagadeesh Moodera, leader of the current work and a senior research scientist in MIT’s Department of Physics. Moodera is also affiliated with the Materials Research Laboratory, the Francis Bitter Magnet Laboratory, and the Plasma Science and Fusion Center (PSFC).

      The nanoscopic rectangular diode — about 1,000 times thinner than the diameter of a human hair — is easily scalable. Millions could be produced on a single silicon wafer.

      Toward a superconducting switch

      Diodes, devices that allow current to travel easily in one direction but not in the reverse, are ubiquitous in computing systems. Modern semiconductor computer chips contain billions of diode-like devices known as transistors. However, these devices can get very hot due to electrical resistance, requiring vast amounts of energy to cool the high-power systems in the data centers behind myriad modern technologies, including cloud computing. According to a 2018 news feature in Nature, these systems could use nearly 20 percent of the world’s power in 10 years.

      As a result, work toward creating diodes made of superconductors has been a hot topic in condensed matter physics. That’s because superconductors transmit current with no resistance at all below a certain low temperature (the critical temperature), and are therefore much more efficient than their semiconducting cousins, which have noticeable energy loss in the form of heat.

      Until now, however, other approaches to the problem have involved much more complicated physics. “The effect we found is due [in part] to a ubiquitous property of superconductors that can be realized in a very simple, straightforward manner. It just stares you in the face,” says Moodera.

      Says Moll of the Max Planck Institute, “The work is an important counterpoint to the current fashion to associate superconducting diodes [with] exotic physics, such as finite-momentum pairing states. While in reality, a superconducting diode is a common and widespread phenomenon present in classical materials, as a result of certain broken symmetries.”

      A somewhat serendipitous discovery

      In 2020 Moodera and colleagues observed evidence of an exotic particle pair known as Majorana fermions. These particle pairs could lead to a new family of topological qubits, the building blocks of quantum computers. While pondering approaches to creating superconducting diodes, the team realized that the material platform they developed for the Majorana work might also be applied to the diode problem.

      They were right. Using that general platform, they developed different iterations of superconducting diodes, each more efficient than the last. The first, for example, consisted of a nanoscopically thin layer of vanadium, a superconductor, which was patterned into a structure common to electronics (the Hall bar). When they applied a tiny magnetic field comparable to the Earth’s magnetic field, they saw the diode effect — a giant polarity dependence for current flow.

      They then created another diode, this time layering a superconductor with a ferromagnet (a ferromagnetic insulator in their case), a material that produces its own tiny magnetic field. After applying a tiny magnetic field to magnetize the ferromagnet so that it produces its own field, they found an even bigger diode effect that was stable even after the original magnetic field was turned off.

      Ubiquitous properties

      The team went on to figure out what was happening.

      In addition to transmitting current with no resistance, superconductors also have other, less well-known but just as ubiquitous properties. For example, they don’t like magnetic fields getting inside. When exposed to a tiny magnetic field, superconductors produce an internal supercurrent that induces its own magnetic flux that cancels the external field, thereby maintaining their superconducting state. This phenomenon, known as the Meissner screening effect, can be thought of as akin to our bodies’ immune system releasing antibodies to fight the infection of bacteria and other pathogens. This works, however, only up to some limit. Similarly, superconductors cannot entirely keep out large magnetic fields.

      The diodes the team created make use of this universal Meissner screening effect. The tiny magnetic field they applied — either directly, or through the adjacent ferromagnetic layer — activates the material’s screening current mechanism for expelling the external magnetic field and maintaining superconductivity.

      The team also found that another key factor in optimizing these superconductor diodes is tiny differences between the two sides, or edges, of the diode devices. These differences “create some sort of asymmetry in the way the magnetic field enters the superconductor,” Moodera says.

      By engineering their own form of edges on diodes to optimize these differences — for example, one edge with sawtooth features, while the other edge not intentionally altered — the team found that they could increase the efficiency from 20 percent to more than 50 percent. This discovery opens the door for devices whose edges could be “tuned” for even higher efficiencies, Moodera says.

      In sum, the team discovered that the edge asymmetries within superconducting diodes, the ubiquitous Meissner screening effect found in all superconductors, and a third property of superconductors known as vortex pinning all came together to produce the diode effect.

      “It is fascinating to see how inconspicuous yet ubiquitous factors can create a significant effect in observing the diode effect,” says Yasen Hou, first author of the paper and a postdoc at the Francis Bitter Magnet Laboratory and the PSFC. “What’s more exciting is that [this work] provides a straightforward approach with huge potential to further improve the efficiency.”

      Christoph Strunk is a professor at the University of Regensburg in Germany. Says Strunk, who was not involved in the research, “the present work demonstrates that the supercurrent in simple superconducting strips can become nonreciprocal. Moreover, when combined with a ferromagnetic insulator, the diode effect can even be maintained in the absence of an external magnetic field. The rectification direction can be programmed by the remnant magnetization of the magnetic layer, which may have high potential for future applications. The work is important and appealing both from the basic research and from the applications point of view.”

      Teenage contributors

      Moodera noted that the two researchers who created the engineered edges did so while still in high school during a summer at Moodera’s lab. They are Ourania Glezakou-Elbert of Richland, Washington, who will be going to Princeton University this fall, and Amith Varambally of Vestavia Hills, Alabama, who will be entering Caltech.

      Says Varambally, “I didn’t know what to expect when I set foot in Boston last summer, and certainly never expected to [be] a coauthor in a Physical Review Letters paper.

      “Every day was exciting, whether I was reading dozens of papers to better understand the diode phenomena, or operating machinery to fabricate new diodes for study, or engaging in conversations with Ourania, Dr. Hou, and Dr. Moodera about our research.

      “I am profoundly grateful to Dr. Moodera and Dr. Hou for providing me with the opportunity to work on such a fascinating project, and to Ourania for being a great research partner and friend.”

      In addition to Moodera and Hou, corresponding authors of the paper are professors Patrick A. Lee of the MIT Department of Physics and Akashdeep Kamra of Autonomous University of Madrid. Other authors from MIT are Liang Fu and Margarita Davydova of the Department of Physics, and Hang Chi, Alessandro Lodesani, and Yingying Wu, all of the Francis Bitter Magnet Laboratory and the Plasma Science and Fusion Center. Chi is also affiliated with the U.S. Army CCDC Research Laboratory.

      Authors also include Fabrizio Nichele, Markus F. Ritter, and Daniel Z. Haxwell of IBM Research Europe; Stefan Ilićof Materials Physics Center (CFM-MPC); and F. Sebastian Bergeret of CFM-MPC and Donostia International Physics Center.

      This work was supported by the Air Force Office of Sponsored Research, the Office of Naval Research, the National Science Foundation, and the Army Research Office. Additional funders are the European Research Council, the European Union’s Horizon 2020 Research and Innovation Framework Programme, the Spanish Ministry of Science and Innovation, the A. v. Humboldt Foundation, and the Department of Energy’s Office of Basic Sciences. More

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      in Environment

      Harnessing synthetic biology to make sustainable alternatives to petroleum products

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      Reducing our reliance on fossil fuels is going to require a transformation in the way we make things. That’s because the hydrocarbons found in fuels like crude oil, natural gas, and coal are also in everyday items like plastics, clothing, and cosmetics.

      Now Visolis, founded by Deepak Dugar SM ’11, MBA ’13, PhD ’13, is combining synthetic biology with chemical catalysis to reinvent the way the world makes things — and reducing gigatons of greenhouse gas emissions in the process.

      The company — which uses a microbe to ferment biomass waste like wood chips and create a molecular building block called mevalonic acid — is more sustainably producing everything from car tires and cosmetics to aviation fuels by tweaking the chemical processes involved to make different byproducts.

      “We started with [the rubber component] isoprene as the main molecule we produce [from mevalonic acid], but we’ve expanded our platform with this unique combination of chemistry and biology that allows us to decarbonize multiple supply chains very rapidly and efficiently,” Dugar explains. “Imagine carbon-negative yoga pants. We can make that happen. Tires can be carbon-negative, personal care can lower its footprint — and we’re already selling into personal care. So in everything from personal care to apparel to industrial goods, our platform is enabling decarbonization of manufacturing.”

      “Carbon-negative” is a term Dugar uses a lot. Visolis has already partnered with some of the world’s largest consumers of isoprene, a precursor to rubber, and now Dugar wants to prove out the company’s process in other emissions-intensive industries.

      “Our process is carbon-negative because plants are taking CO2 from the air, and we take that plant matter and process it into something structural, like synthetic rubber, which is used for things like roofing, tires, and other applications,” Dugar explains. “Generally speaking, most of that material at the end of its life gets recycled, for example to tarmac or road, or, worst-case scenario, it ends up in a landfill, so the CO2 that was captured by the plant matter stays captured in the materials. That means our production can be carbon-negative depending on the emissions of the production process. That allows us to not only reduce climate change but start reversing it. That was an insight I had about 10 years ago at MIT.”

      Finding a path

      For his PhD, Dugar explored the economics of using microbes to make high-octane gas additives. He also took classes at the MIT Sloan School of Management on sustainability and entrepreneurship, including the particularly influential course 15.366 (Climate and Energy Ventures). The experience inspired him to start a company.

      “I wanted to work on something that could have the largest climate impact, and that was replacing petroleum,” Dugar says. “It was about replacing petroleum not just as a fuel but as a material as well. Everything from the clothes we wear to the furniture we sit on is often made using petroleum.”

      By analyzing recent advances in synthetic biology and making some calculations from first principles, Dugar decided that a microbial approach to cleaning up the production of rubber was viable. He participated in the MIT Clean Energy Prize and worked with others at MIT to prove out the idea. But it was still just an idea. After graduation, he took a consulting job at a large company, spending his nights and weekends renting lab space to continue trying to make his sustainable rubber a reality.

      After 18 months, by applying engineering concepts like design-for-scale to synthetic biology, Dugar was able to develop a microbe that met 80 percent of his criteria for making an intermediate molecule called mevalonic acid. From there, he developed a chemical catalysis process that converted mevalonic acid to isoprene, the main component of natural rubber. Visolis has since patented other chemical conversion processes that turn mevalonic acid to aviation fuel, polymers, and fabrics.

      Dugar left his consulting job in 2014 and was awarded a fellowship to work on Visolis full-time at the Lawrence Berkeley National Lab via Activate, an incubator empowering scientists to reinvent the world.

      From rubber to jet fuels

      Today, in addition to isoprene, Visolis is selling skin care products through the brand Ameva Bio, which produces mevalonic acid-based creams by recycling plant byproducts created in other processes. The company offers refillable bottles and even offsets emissions from the shipping of its products.

      “We are working throughout the supply chain,” Dugar says. “It made sense to clean up the isoprene part of the rubber supply chain rather than the entire supply chain. But we’re also producing molecules for skin that are better for you, so you can put something much more sustainable and healthier on your body instead of petrochemicals. We launched Ameva to demonstrate that brands can leverage synthetic biology to turn carbon-negative ingredients into high-performing products.”

      Visolis is also starting the process of gaining regulatory approval for its sustainable aviation fuel, which Dugar believes could have the biggest climate impact of any of the company’s products by cleaning up the production of fuels for commercial flight.

      “We’re working with leading companies to help them decarbonize aviation” Dugar says. “If you look at the lifecycle of fuel, the current petroleum-based approach is we dig out hydrocarbons from the ground and burn it, emitting CO2 into the air. In our process, we take plant matter, which affixes to CO2 and captures renewable energy in those bonds, and then we transfer that into aviation fuel plus things like synthetic rubber, yoga pants, and other things that continue to hold the carbon. So, our factories can still operate at net zero carbon emissions.”

      Visolis is already generating millions of dollars in revenue, and Dugar says his goal is to scale the company rapidly now that its platform molecule has been validated.

      “We have been scaling our technology by 10 times every two to three years and are now looking to increase deployment of our technology at the same pace, which is very exciting.” Dugar says. “If you extrapolate that, very quickly you get to massive impact. That’s our goal.” More

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      in Energy

      Addressing food insecurity in arid regions with an open-source evaporative cooling chamber design

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      Anyone who has ever perspired on a hot summer day understands the principle — and critical value — of evaporative cooling. Our bodies produce droplets of sweat when we overheat, and with a dry breeze or nearby fan those droplets will evaporate, absorbing heat in the process creating a welcome cool feeling.

      That same scientific principle, known as evaporative cooling, can be a game-changer for preserving fruits and vegetables grown on smallholder farms, where the wilting dry heat can quickly degrade freshly harvested produce. If those just-picked red peppers and leafy greens are not consumed in short order, or quickly transferred to cold — or at least cool — storage, much of it can go to waste.

      Now, MIT Professor Leon Glicksman of the Building Technology Program within the Department of Architecture, and Research Engineer Eric Verploegen of MIT D-Lab have released their open-source design for a forced-air evaporative cooling chamber that can be built in a used shipping container and powered by either grid electricity or built-in solar panels. With a capacity of 168 produce crates, the chamber offers great promise for smallholder farmers in hot, dry climates who need an affordable method for quickly bringing down the temperature of freshly harvested fruit and vegetables to ensure they stay fresh.

      “Delicate fruits and vegetables are most vulnerable to spoilage if they are picked during the day,” says Verploegen, a longtime proponent of using evaporative cooling to reduce post-harvest waste. “And if refrigerated cold rooms aren’t feasible or affordable,” he continues, “evaporative cooling can make a big difference for farmers and the communities they feed.”

      Verploegen has made evaporative cooling the focus of his work since 2016, initially focusing on small-scale evaporative cooling “Zeer” pots, typically with a capacity between 10 and 100 liters and great for household use, as well as larger double-brick-walled chambers known as zero-energy cooling chambers or ZECCs, which can store between six and 16 vegetable crates at a time. These designs rely on passive airflow. The newly released design for the forced-air evaporative cooling chamber is differentiated from these two more modest designs by the active airflow system, as well as by significantly larger capacity.

      In 2019, Verploegen turned his attention to the idea of building a larger evaporative cooling room and joined forces with Glicksman to explore using forced, instead of passive, airflow to cool fruit and vegetables. After studying existing cold storage options and conducting user research with farmers in Kenya, they came up with the idea to use active evaporative cooling with a used shipping container as the structure of the chamber. As the Covid-19 pandemic was ramping up in 2020, they procured a used 10-foot shipping container, installed it in the courtyard area outside D-Lab near Village Street, and went to work on a prototype of the forced-air evaporative cooling chamber.

      Here’s how it works: Industrial fans draw hot, dry air into the chamber, which is passed through a porous wet pad. The resulting cool and humid air is then forced through the crates of fruits and vegetables stored inside the chamber. The air is then directed through the raised floor and to a channel between the insulation and the exterior container wall, where it flows to the exhaust holes near the top of the side walls.

      Leon Glicksman, a professor of building technology and mechanical engineering, drew on his previous research in natural ventilation and airflow in buildings to come up with the vertical forced-air design pattern for the chamber. “The key to the design is the close control of the airflow strength, and its direction,” he says. “The strength of the airflow passing directly through the crates of fruits and vegetables, and the airflow pathway itself, are what makes this system work so well. The design promotes rapid cooling of a harvest taken directly from the field.”

      In addition to the novel and effective airflow system, the forced-air evaporative cooling chamber represents so much of what D-Lab is known for in its work in low-resourced and off-grid communities: developing low-cost and low-carbon-footprint technologies with partners. Evaporative cooling is no different. Whether connected to the electrical grid or run from solar panels, the forced-air chamber consumes one-quarter the power of refrigerated cold rooms. And, as the chamber is designed to be built in a used shipping container — ubiquitous the world over — the project is a great example of up-cycling.

      Piloting the design

      As with earlier investigations, Verploegen, Glicksman, and their colleagues have worked closely with farmers and community members. For the forced-air system, the team engaged with community partners who are living the need for better cooling and storage conditions for their produce in the climate conditions where evaporative cooling works best. Two partners, one in Kenya and one in India, each built a pilot chamber, testing and informing the process alongside the work being done at MIT.

      In Kenya, where smallholder farms produce 63 percent of total food consumed and over 50 percent of smallholder produce is lost post-harvest, they worked with Solar Freeze, a cold storage company located in in Kibwezi, Kenya. Solar Freeze, whose founder Dysmus Kisilu was a 2019 MIT D-Lab Scale-Ups Fellow, built an off-grid forced-air evaporative cooling chamber at a produce market between Nairobi and Mombasa at a cost of $15,000, powered by solar photovoltaic panels. “The chamber is offering a safety net against huge post-harvest losses previously experienced by local smallholder farmers,” comments Peter Mumo, an entrepreneur and local politician who oversaw the construction of the Solar Freeze chamber in Makuni County, Kenya.

      As much as 30 percent of fruits and vegetables produced in India are wasted each year due to insufficient cold storage capacity, lack of cold storage close to farms, poor transportation infrastructure, and other gaps in the cold chain. Although the climate varies across the subcontinent, the hot desert climate there, such as in Bhuj where the Hunnarshala Foundation is headquartered, is perfect for evaporative cooling. Hunnarshala signed on to build an on-grid system for $8,100, which they located at an organic farm near Bhuj. “We have really encouraging results,” says Mahavir Acharya, executive director of Hunnarshala Foundation. “In peak summer, when the temperature is 42 [Celsius] we are able to get to 26 degrees [Celsius] inside and 95 percent humidity, which is really good conditions for vegetables to remain fresh for three, four, five, six days. In winter we tested [and saw temperatures reduced from] 35 degrees to 24 degrees [Celsius], and for seven days the quality was quite good.”

      Getting the word out

      With the concept validated and pilots well established, the next step is spreading the word.

      “We’re continuing to test and optimize the system, both in Kenya and India, as well as our test chambers here at MIT,” says Verploegen. “We will continue piloting with users and deploying with farmers and vendors, gathering data on the thermal performance, the shelf life of fruits and vegetables in the chamber, and how using the technology impacts the users. And, we’re also looking to engage with cold storage providers who might want to build this or others in the horticulture value chain such as farmer cooperatives, individual farmers, and local governments.”

      To reach the widest number of potential users, Verploegen and the team chose not to pursue a patent and instead set up a website to disseminate the open-source design with detailed guidance on how to build a forced-air evaporative cooling chamber. In addition to the extensive printed documentation, well-illustrated with detailed CAD drawings and video, the team has created instructional videos.

      As co-principal investigator in the early stages of the project, MIT professor of mechanical engineering Dan Frey contributed to the market research phase of the project and the initial conception of chamber design. “These forced-air evaporative cooling chambers have great potential, and the open-source approach is an excellent choice for this project,” says Frey. “The design’s release is a significant milestone on the path to positive impacts.”

      The forced-air evaporative cooling chamber research and design have been supported by the Abdul Latif Jameel Water and Food Systems Lab through an India Grant, Seed Grant, and a Solutions Grant. More