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    New filtration material could remove long-lasting chemicals from water

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    Water contamination by the chemicals used in today’s technology is a rapidly growing problem globally. A recent study by the U.S. Centers for Disease Control found that 98 percent of people tested had detectable levels of PFAS, a family of particularly long-lasting compounds also known as “forever chemicals,” in their bloodstream.A new filtration material developed by researchers at MIT might provide a nature-based solution to this stubborn contamination issue. The material, based on natural silk and cellulose, can remove a wide variety of these persistent chemicals as well as heavy metals. And, its antimicrobial properties can help keep the filters from fouling.The findings are described in the journal ACS Nano, in a paper by MIT postdoc Yilin Zhang, professor of civil and environmental engineering Benedetto Marelli, and four others from MIT.PFAS chemicals are present in a wide range of products, including cosmetics, food packaging, water-resistant clothing, firefighting foams, and antistick coating for cookware. A recent study identified 57,000 sites contaminated by these chemicals in the U.S. alone. The U.S. Environmental Protection Agency has estimated that PFAS remediation will cost $1.5 billion per year, in order to meet new regulations that call for limiting the compound to less than 7 parts per trillion in drinking water.Contamination by PFAS and similar compounds “is actually a very big deal, and current solutions may only partially resolve this problem very efficiently or economically,” Zhang says. “That’s why we came up with this protein and cellulose-based, fully natural solution,” he says.“We came to the project by chance,” Marelli notes. The initial technology that made the filtration material possible was developed by his group for a completely unrelated purpose — as a way to make a labelling system to counter the spread of counterfeit seeds, which are often of inferior quality. His team devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils,” through an environmentally benign, water-based drop-casting method at room temperature.Zhang suggested that their new nanofibrillar material might be effective at filtering contaminants, but initial attempts with the silk nanofibrils alone didn’t work. The team decided to try adding another material: cellulose, which is abundantly available and can be obtained from agricultural wood pulp waste. The researchers used a self-assembly method in which the silk fibroin protein is suspended in water and then templated into nanofibrils by inserting “seeds” of cellulose nanocrystals. This causes the previously disordered silk molecules to line up together along the seeds, forming the basis of a hybrid material with distinct new properties.By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests.

    By integrating cellulose into the silk-based fibrils that could be formed into a thin membrane, and then tuning the electrical charge of the cellulose, the researchers produced a material that was highly effective at removing contaminants in lab tests. Pictured is an example of the filter.

    Image: Courtesy of the researchers

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    The electrical charge of the cellulose, they found, also gave it strong antimicrobial properties. This is a significant advantage, since one of the primary causes of failure in filtration membranes is fouling by bacteria and fungi. The antimicrobial properties of this material should greatly reduce that fouling issue, the researchers say.“These materials can really compete with the current standard materials in water filtration when it comes to extracting metal ions and these emerging contaminants, and they can also outperform some of them currently,” Marelli says. In lab tests, the materials were able to extract orders of magnitude more of the contaminants from water than the currently used standard materials, activated carbon or granular activated carbon.While the new work serves as a proof of principle, Marelli says, the team plans to continue working on improving the material, especially in terms of durability and availability of source materials. While the silk proteins used can be available as a byproduct of the silk textile industry, if this material were to be scaled up to address the global needs for water filtration, the supply might be insufficient. Also, alternative protein materials may turn out to perform the same function at lower cost.Initially, the material would likely be used as a point-of-use filter, something that could be attached to a kitchen faucet, Zhang says. Eventually, it could be scaled up to provide filtration for municipal water supplies, but only after testing demonstrates that this would not pose any risk of introducing any contamination into the water supply. But one big advantage of the material, he says, is that both the silk and the cellulose constituents are considered food-grade substances, so any contamination is unlikely.“Most of the normal materials available today are focusing on one class of contaminants or solving single problems,” Zhang says. “I think we are among the first to address all of these simultaneously.”“What I love about this approach is that it is using only naturally grown materials like silk and cellulose to fight pollution,” says Hannes Schniepp, professor of applied science at the College of William and Mary, who was not associated with this work. “In competing approaches, synthetic materials are used — which usually require only more chemistry to fight some of the adverse outcomes that chemistry has produced. [This work] breaks this cycle! … If this can be mass-produced in an economically viable way, this could really have a major impact.”The research team included MIT postdocs Hui Sun and Meng Li, graduate student Maxwell Kalinowski, and recent graduate Yunteng Cao PhD ’22, now a postdoc at Yale University. The work was supported by the U.S. Office of Naval Research, the U.S. National Science Foundation, and the Singapore-MIT Alliance for Research and Technology. More

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      Study reveals the benefits and downside of fasting

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      Low-calorie diets and intermittent fasting have been shown to have numerous health benefits: They can delay the onset of some age-related diseases and lengthen lifespan, not only in humans but many other organisms.Many complex mechanisms underlie this phenomenon. Previous work from MIT has shown that one way fasting exerts its beneficial effects is by boosting the regenerative abilities of intestinal stem cells, which helps the intestine recover from injuries or inflammation.In a study of mice, MIT researchers have now identified the pathway that enables this enhanced regeneration, which is activated once the mice begin “refeeding” after the fast. They also found a downside to this regeneration: When cancerous mutations occurred during the regenerative period, the mice were more likely to develop early-stage intestinal tumors.“Having more stem cell activity is good for regeneration, but too much of a good thing over time can have less favorable consequences,” says Omer Yilmaz, an MIT associate professor of biology, a member of MIT’s Koch Institute for Integrative Cancer Research, and the senior author of the new study.Yilmaz adds that further studies are needed before forming any conclusion as to whether fasting has a similar effect in humans.“We still have a lot to learn, but it is interesting that being in either the state of fasting or refeeding when exposure to mutagen occurs can have a profound impact on the likelihood of developing a cancer in these well-defined mouse models,” he says.MIT postdocs Shinya Imada and Saleh Khawaled are the lead authors of the paper, which appears today in Nature.Driving regenerationFor several years, Yilmaz’s lab has been investigating how fasting and low-calorie diets affect intestinal health. In a 2018 study, his team reported that during a fast, intestinal stem cells begin to use lipids as an energy source, instead of carbohydrates. They also showed that fasting led to a significant boost in stem cells’ regenerative ability.However, unanswered questions remained: How does fasting trigger this boost in regenerative ability, and when does the regeneration begin?“Since that paper, we’ve really been focused on understanding what is it about fasting that drives regeneration,” Yilmaz says. “Is it fasting itself that’s driving regeneration, or eating after the fast?”In their new study, the researchers found that stem cell regeneration is suppressed during fasting but then surges during the refeeding period. The researchers followed three groups of mice — one that fasted for 24 hours, another one that fasted for 24 hours and then was allowed to eat whatever they wanted during a 24-hour refeeding period, and a control group that ate whatever they wanted throughout the experiment.The researchers analyzed intestinal stem cells’ ability to proliferate at different time points and found that the stem cells showed the highest levels of proliferation at the end of the 24-hour refeeding period. These cells were also more proliferative than intestinal stem cells from mice that had not fasted at all.“We think that fasting and refeeding represent two distinct states,” Imada says. “In the fasted state, the ability of cells to use lipids and fatty acids as an energy source enables them to survive when nutrients are low. And then it’s the postfast refeeding state that really drives the regeneration. When nutrients become available, these stem cells and progenitor cells activate programs that enable them to build cellular mass and repopulate the intestinal lining.”Further studies revealed that these cells activate a cellular signaling pathway known as mTOR, which is involved in cell growth and metabolism. One of mTOR’s roles is to regulate the translation of messenger RNA into protein, so when it’s activated, cells produce more protein. This protein synthesis is essential for stem cells to proliferate.The researchers showed that mTOR activation in these stem cells also led to production of large quantities of polyamines — small molecules that help cells to grow and divide.“In the refed state, you’ve got more proliferation, and you need to build cellular mass. That requires more protein, to build new cells, and those stem cells go on to build more differentiated cells or specialized intestinal cell types that line the intestine,” Khawaled says.Too much of a good thingThe researchers also found that when stem cells are in this highly regenerative state, they are more prone to become cancerous. Intestinal stem cells are among the most actively dividing cells in the body, as they help the lining of the intestine completely turn over every five to 10 days. Because they divide so frequently, these stem cells are the most common source of precancerous cells in the intestine.In this study, the researchers discovered that if they turned on a cancer-causing gene in the mice during the refeeding stage, they were much more likely to develop precancerous polyps than if the gene was turned on during the fasting state. Cancer-linked mutations that occurred during the refeeding state were also much more likely to produce polyps than mutations that occurred in mice that did not undergo the cycle of fasting and refeeding.“I want to emphasize that this was all done in mice, using very well-defined cancer mutations. In humans it’s going to be a much more complex state,” Yilmaz says. “But it does lead us to the following notion: Fasting is very healthy, but if you’re unlucky and you’re refeeding after a fasting, and you get exposed to a mutagen, like a charred steak or something, you might actually be increasing your chances of developing a lesion that can go on to give rise to cancer.”Yilmaz also noted that the regenerative benefits of fasting could be significant for people who undergo radiation treatment, which can damage the intestinal lining, or other types of intestinal injury. His lab is now studying whether polyamine supplements could help to stimulate this kind of regeneration, without the need to fast.“This fascinating study provides insights into the complex interplay between food consumption, stem cell biology, and cancer risk,” says Ophir Klein, a professor of medicine at the University of California at San Francisco and Cedars-Sinai Medical Center, who was not involved in the study. “Their work lays a foundation for testing polyamines as compounds that may augment intestinal repair after injuries, and it suggests that careful consideration is needed when planning diet-based strategies for regeneration to avoid increasing cancer risk.”The research was funded, in part, by a Pew-Stewart Trust Scholar award, the Marble Center for Cancer Nanomedicine, the Koch Institute-Dana Farber/Harvard Cancer Center Bridge Project, and the MIT Stem Cell Initiative. More

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      Pioneering the future of materials extraction

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      The next time you cook pasta, imagine that you are cooking spaghetti, rigatoni, and seven other varieties all together, and they need to be separated onto 10 different plates before serving. A colander can remove the water — but you still have a mound of unsorted noodles. Now imagine that this had to be done for thousands of tons of pasta a day. That gives you an idea of the scale of the problem facing Brendan Smith PhD ’18, co-founder and CEO of SiTration, a startup formed out of MIT’s Department of Materials Science and Engineering (DMSE) in 2020. SiTration, which raised $11.8 million in seed capital led by venture capital firm 2150 earlier this month, is revolutionizing the extraction and refining of copper, cobalt, nickel, lithium, precious metals, and other materials critical to manufacturing clean-energy technologies such as electric motors, wind turbines, and batteries. Its initial target applications are recovering the materials from complex mining feed streams, spent lithium-ion batteries from electric vehicles, and various metals refining processes. The company’s breakthrough lies in a new silicon membrane technology that can be adjusted to efficiently recover disparate materials, providing a more sustainable and economically viable alternative to conventional, chemically intensive processes. Think of a colander with adjustable pores to strain different types of pasta. SiTration’s technology has garnered interest from industry players, including mining giant Rio Tinto. Some observers may question whether targeting such different industries could cause the company to lose focus. “But when you dig into these markets, you discover there is actually a significant overlap in how all of these materials are recovered, making it possible for a single solution to have impact across verticals,” Smith says.Powering up materials recoveryConventional methods of extracting critical materials in mining, refining, and recycling lithium-ion batteries involve heavy use of chemicals and heat, which harm the environment. Typically, raw ore from mines or spent batteries are ground into fine particles before being dissolved in acid or incinerated in a furnace. Afterward, they undergo intensive chemical processing to separate and purify the valuable materials. “It requires as much as 10 tons of chemical input to produce one ton of critical material recovered from the mining or battery recycling feedstock,” says Smith. Operators can then sell the recaptured materials back into the supply chain, but suffer from wide swings in profitability due to uncertain market prices. Lithium prices have been the most volatile, having surged more than 400 percent before tumbling back to near-original levels in the past two years. Despite their poor economics and negative environmental impact, these processes remain the state of the art today. By contrast, SiTration is electrifying the critical-materials recovery process, improving efficiency, producing less chemical waste, and reducing the use of chemicals and heat. What’s more, the company’s processing technology is built to be highly adaptable, so it can handle all kinds of materials. The core technology is based on work done at MIT to develop a novel type of membrane made from silicon, which is durable enough to withstand harsh chemicals and high temperatures while conducting electricity. It’s also highly tunable, meaning it can be modified or adjusted to suit different conditions or target specific materials. SiTration’s technology also incorporates electro-extraction, a technique that uses electrochemistry to further isolate and extract specific target materials. This powerful combination of methods in a single system makes it more efficient and effective at isolating and recovering valuable materials, Smith says. So depending on what needs to be separated or extracted, the filtration and electro-extraction processes are adjusted accordingly. “We can produce membranes with pore sizes from the molecular scale up to the size of a human hair in diameter, and everything in between. Combined with the ability to electrify the membrane and separate based on a material’s electrochemical properties, this tunability allows us to target a vast array of different operations and separation applications across industrial fields,” says Smith. Efficient access to materials like lithium, cobalt, and copper — and precious metals like platinum, gold, silver, palladium, and rare-earth elements — is key to unlocking innovation in business and sustainability as the world moves toward electrification and away from fossil fuels.“This is an era when new materials are critical,” says Professor Jeffrey Grossman, co-founder and chief scientist of SiTration and the Morton and Claire Goulder and Family Professor in Environmental Systems at DMSE. “For so many technologies, they’re both the bottleneck and the opportunity, offering tremendous potential for non-incremental advances. And the role they’re having in commercialization and in entrepreneurship cannot be overstated.”SiTration’s commercial frontierSmith became interested in separation technology in 2013 as a PhD student in Grossman’s DMSE research group, which has focused on the design of new membrane materials for a range of applications. The two shared a curiosity about separation of critical materials and a hunger to advance the technology. After years of study under Grossman’s mentorship, and with support from several MIT incubators and foundations including the Abdul Latif Jameel Water and Food Systems Lab’s Solutions Program, the Deshpande Center for Technological Innovation, the Kavanaugh Fellowship, MIT Sandbox, and Venture Mentoring Service, Smith was ready to officially form SiTration in 2020. Grossman has a seat on the board and plays an active role as a strategic and technical advisor. Grossman is involved in several MIT spinoffs and embraces the different imperatives of research versus commercialization. “At SiTration, we’re driving this technology to work at scale. There’s something super exciting about that goal,” he says. “The challenges that come with scaling are very different than the challenges that come in a university lab.” At the same time, although not every research breakthrough becomes a commercial product, open-ended, curiosity-driven knowledge pursuit holds its own crucial value, he adds.It has been rewarding for Grossman to see his technically gifted student and colleague develop a host of other skills the role of CEO demands. Getting out to the market and talking about the technology with potential partners, putting together a dynamic team, discovering the challenges facing industry, drumming up support, early on — those became the most pressing activities on Smith’s agenda. “What’s most fun to me about being a CEO of an early-stage startup is that there are 100 different factors, most people-oriented, that you have to navigate every day. Each stakeholder has different motivations and objectives. And you basically try to fit that all together, to create value for our partners and customers, the company, and for society,” says Smith. “You start with just an idea, and you have to keep leveraging that to form a more and more tangible product, to multiply and progress commercial relationships, and do it all at an ever-expanding scale.” MIT DNA runs deep in the nine-person company, with DMSE grad and former Grossman student Jatin Patil as director of product; Ahmed Helal, from MIT’s Department of Mechanical Engineering, as vice president of research and development; Daniel Bregante, from the Department of Chemistry, as VP of technology; and Sarah Melvin, from the departments of Physics and Political Science, as VP of strategy and operations. Melvin is the first hire devoted to business development. Smith plans to continue expanding the team following the closing of the company’s seed round.  Strategic alliancesBeing a good communicator was important when it came to securing funding, Smith says. SiTration received $2.35 million in pre-seed funding in 2022 led by Azolla Ventures, which reserves its $239 million in investment capital for startups that would not otherwise easily obtain funding. “We invest only in solution areas that can achieve gigaton-scale climate impact by 2050,” says Matthew Nordan, a general partner at Azolla and now SiTration board member. The MIT-affiliated E14 Fund also contributed to the pre-seed round; Azolla and E14 both participated in the recent seed funding round. “Brendan demonstrated an extraordinary ability to go from being a thoughtful scientist to a business leader and thinker who has punched way above his weight in engaging with customers and recruiting a well-balanced team and navigating tricky markets,” says Nordan. One of SiTration’s first partnerships is with Rio Tinto, one of the largest mining companies in the world. As SiTration evaluated various uses cases in its early days, identifying critical materials as its target market, Rio Tinto was looking for partners to recover valuable metals such as cobalt and copper from the wastewater generated at mines. These metals were typically trapped in the water, creating harmful waste and resulting in lost revenue. “We thought this was a great innovation challenge and posted it on our website to scout for companies to partner with who can help us solve this water challenge,” said Nick Gurieff, principal advisor for mine closure, in an interview with MIT’s Industrial Liaison Program in 2023. At SiTration, mining was not yet a market focus, but Smith couldn’t help noticing that Rio Tinto’s needs were in alignment with what his young company offered. SiTration submitted its proposal in August 2022. Gurieff said SiTration’s tunable membrane set it apart. The companies formed a business partnership in June 2023, with SiTration adjusting its membrane to handle mine wastewater and incorporating Rio Tinto feedback to refine the technology. After running tests with water from mine sites, SiTration will begin building a small-scale critical-materials recovery unit, followed by larger-scale systems processing up to 100 cubic meters of water an hour.SiTration’s focused technology development with Rio Tinto puts it in a good position for future market growth, Smith says. “Every ounce of effort and resource we put into developing our product is geared towards creating real-world value. Having an industry-leading partner constantly validating our progress is a tremendous advantage.”It’s a long time from the days when Smith began tinkering with tiny holes in silicon in Grossman’s DMSE lab. Now, they work together as business partners who are scaling up technology to meet a global need. Their joint passion for applying materials innovation to tough problems has served them well. “Materials science and engineering is an engine for a lot of the innovation that is happening today,” Grossman says. “When you look at all of the challenges we face to make the transition to a more sustainable planet, you realize how many of these are materials challenges.” More

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      Sophia Chen: It’s our duty to make the world better through empathy, patience, and respect

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      Sophia Chen, a fifth-year senior double majoring in mechanical engineering and art and design, learned about MIT D-Lab when she was a Florida middle schooler. She drove with her family from their home in Clearwater to Tampa to an MIT informational open house for prospective students. There, she heard about a moringa seed press that had been developed by D-Lab students. Those students, Kwami Williams ’12 and Emily Cunningham (a cross-registered Harvard University student), went on to found MoringaConnect with a goal of increasing Ghanaian farmer incomes. Over the past 12 years, the company has done just that, sometimes by a factor of 10 or more, by selling to wholesalers and establishing their own line of moringa skin and hair care products, as well as nutritional supplements and teas.“I remember getting chills,” says Sophia. “I was so in awe. MIT had always been my dream college growing up, but hearing this particular story truly cemented that dream. I even talked about D-Lab during my admissions interview. Once I came to MIT, I knew I had to take a D-Lab class — and now, at the end of my five years, I’ve taken four.”Taking four D-Lab classes during her undergraduate years may make Sophia exceptional, though not unusual. Of the nearly 4,000 enrollments in D-Lab classes over the past 22 years, as many as 20 percent took at least two classes, and many take three or more by the time the graduate. For Sophia, her D-Lab classes were a logical progression that both confirmed and expanded her career goals in global medicine.Centering the role of project community partnersSophia’s first D-Lab class was 2.722J / EC.720 (D-Lab: Design). Like all D-Lab classes, D-Lab: Design is project-based and centers the knowledge and contributions of each project’s community partner. Her team worked with a group in Uganda called Safe Water Harvesters on a project aimed at creating a solar-powered atmospheric water harvester using desiccants. They focused on early research and development for the desiccant technology by running tests for vapor absorption. Safe Water Harvesters designed the parameters and goals of the project and collaborated with the students remotely throughout the semester.Safe Water Harvesters’ role in the project was key to the project’s success. “At D-Lab, I learned the importance of understanding that solutions in international development must come from the voices and needs of people whom the intervention is trying to serve,” she says. “Some of the first questions we were taught to ask are ‘what materials and manufacturing processes are available?’ and ‘how is this technology going to be maintained by the community?’”The link between water access and gender inequityElecting to join the water harvesting project in Uganda was no accident. The previous summer, Sophia had interned with a startup targeting the spread of cholera in developing areas by engineering a new type of rapid detection technology that would sample from users’ local water sources. From there, she joined Professor Amos Winter’s Global Engineering and Research (GEAR) Lab as an Undergraduate Research Opportunities Program student and worked on a point-of-use desalination unit for households in India. Taking EC.715 (D-Lab: Water, Sanitation, and Hygiene) was a logical next step for Sophia. “This class was life-changing,” she says. “I was already passionate about clean water access and global resource equity, but I quickly discovered the complexity of WASH not just as an issue of poverty but as an issue of gender.” She joined a project spearheaded by a classmate from Nepal, which aimed to address the social taboos surrounding menstruation among Nepalese schoolgirls.“This class and project helped me realize that water insecurity and gender inequality — especially gender-based violence — ​are highly intertwined,” comments Sophia. This plays out in a variety of ways. Where there is poor sanitation infrastructure in schools, girls often miss classes or drop out altogether when menstruating. And where water is scarce, women and girls often walk miles to collect water to accommodate daily drinking, cooking, and hygiene needs. During this trek, they are vulnerable to assault and the pressure to engage in transactional sex at water access points.“It became clear to me that women are disproportionately affected by water insecurity, and that water is key to understanding women’s empowerment,” comments Sophia, “and that I wanted to keep learning about the field of development and how it intersects with gender!”So, in fall 2023, Sophia took both 11.025/EC.701 (D-Lab: Development) and WGS.277/EC.718 (D-Lab: Gender and Development). In D-Lab: Development, her team worked with Tatirano, a nongovernmental organization in Madagascar, to develop a vapor-condensing chamber for a water desalination system, a prototype they were able to test and iterate in Madagascar at the end of the semester.Getting out into the world through D-Lab fieldwork“Fieldwork with D-Lab is an eye-opening experience that anyone could benefit from,” says Sophia. “It’s easy to get lost in the MIT and tech bubble. But there’s a whole world out there with people who live such different lives than many of us, and we can learn even more from them than we can from our psets.”For Sophia’s D-Lab: Gender and Development class, she worked with the Society Empowerment Project in Kenya, ultimately traveling there during MIT’s Independent Activities Period last January. In Kenya, she worked with her team to run a workshop with teen parents to identify risk factors prior to pregnancy and postpartum challenges, in order to then ideate and develop solutions such as social programs. “Through my fieldwork in Kenya and Madagascar,” says Sophia, “it became clear how important it is to create community-based solutions that are led and maintained by community members. Solutions need community input, leadership, and trust. Ultimately, this is the only way to have long-lasting, high-impact, sustainable change. One of my D-Lab trip leaders said that you cannot import solutions. I hope all engineers recognize the significance of this statement. It is our duty as engineers and scientists to make the world a better place while carrying values of empathy, patience, and respect.”Pursuing passion and purpose at the intersection of medicine, technology, and policyAfter graduation in June, Sophia will be traveling to South Africa through MISTI Africa to help with a clinical trial and community outreach. She then intends to pursue a master’s in global health and apply to medical school, with the goal of working in global health at the intersection of medicine, technology, and policy.“It is no understatement to say that D-Lab has played a central role in helping me discover what I’m passionate about and what my purpose is in life,” she says. “I hope to dedicate my career towards solving global health inequity and gender inequality.” ​ More

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      Researchers develop a detector for continuously monitoring toxic gases

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      Most systems used to detect toxic gases in industrial or domestic settings can be used only once, or at best a few times. Now, researchers at MIT have developed a detector that could provide continuous monitoring for the presence of these gases, at low cost.The new system combines two existing technologies, bringing them together in a way that preserves the advantages of each while avoiding their limitations. The team used a material called a metal-organic framework, or MOF, which is highly sensitive to tiny traces of gas but whose performance quickly degrades, and combined it with a polymer material that is highly durable and easier to process, but much less sensitive.The results are reported today in the journal Advanced Materials, in a paper by MIT professors Aristide Gumyusenge, Mircea Dinca, Heather Kulik, and Jesus del Alamo, graduate student Heejung Roh, and postdocs Dong-Ha Kim, Yeongsu Cho, and Young-Moo Jo.Highly porous and with large surface areas, MOFs come in a variety of compositions. Some can be insulators, but the ones used for this work are highly electrically conductive. With their sponge-like form, they are effective at capturing molecules of various gases, and the sizes of their pores can be tailored to make them selective for particular kinds of gases. “If you are using them as a sensor, you can recognize if the gas is there if it has an effect on the resistivity of the MOF,” says Gumyusenge, the paper’s senior author and the Merton C. Flemings Career Development Assistant Professor of Materials Science and Engineering.The drawback for these materials’ use as detectors for gases is that they readily become saturated, and then can no longer detect and quantify new inputs. “That’s not what you want. You want to be able to detect and reuse,” Gumyusenge says. “So, we decided to use a polymer composite to achieve this reversibility.”The team used a class of conductive polymers that Gumyusenge and his co-workers had previously shown can respond to gases without permanently binding to them. “The polymer, even though it doesn’t have the high surface area that the MOFs do, will at least provide this recognize-and-release type of phenomenon,” he says.The team combined the polymers in a liquid solution along with the MOF material in powdered form, and deposited the mixture on a substrate, where they dry into a uniform, thin coating. By combining the polymer, with its quick detection capability, and the more sensitive MOFs, in a one-to-one ratio, he says, “suddenly we get a sensor that has both the high sensitivity we get from the MOF and the reversibility that is enabled by the presence of the polymer.”The material changes its electrical resistance when molecules of the gas are temporarily trapped in the material. These changes in resistance can be continuously monitored by simply attaching an ohmmeter to track the resistance over time. Gumyusenge and his students demonstrated the composite material’s ability to detect nitrogen dioxide, a toxic gas produced by many kinds of combustion, in a small lab-scale device. After 100 cycles of detection, the material was still maintaining its baseline performance within a margin of about 5 to 10 percent, demonstrating its long-term use potential.In addition, this material has far greater sensitivity than most presently used detectors for nitrogen dioxide, the team reports. This gas is often detected after the use of stove ovens. And, with this gas recently linked to many asthma cases in the U.S., reliable detection in low concentrations is important. The team demonstrated that this new composite could detect, reversibly, the gas at concentrations as low as 2 parts per million.While their demonstration was specifically aimed at nitrogen dioxide, Gumyusenge says, “we can definitely tailor the chemistry to target other volatile molecules,” as long as they are small polar analytes, “which tend to be most of the toxic gases.”Besides being compatible with a simple hand-held detector or a smoke-alarm type of device, one advantage of the material is that the polymer allows it to be deposited as an extremely thin uniform film, unlike regular MOFs, which are generally in an inefficient powder form. Because the films are so thin, there is little material needed and production material costs could be low; the processing methods could be typical of those used for industrial coating processes. “So, maybe the limiting factor will be scaling up the synthesis of the polymers, which we’ve been synthesizing in small amounts,” Gumyusenge says.“The next steps will be to evaluate these in real-life settings,” he says. For example, the material could be applied as a coating on chimneys or exhaust pipes to continuously monitor gases through readings from an attached resistance monitoring device. In such settings, he says, “we need tests to check if we truly differentiate it from other potential contaminants that we might have overlooked in the lab setting. Let’s put the sensors out in real-world scenarios and see how they do.”The work was supported by the MIT Climate and Sustainability Consortium (MCSC), the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT, and the U.S. Department of Energy. More

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      Repurposed beer yeast may offer a cost-effective way to remove lead from water

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      Every year, beer breweries generate and discard thousands of tons of surplus yeast. Researchers from MIT and Georgia Tech have now come up with a way to repurpose that yeast to absorb lead from contaminated water.Through a process called biosorption, yeast can quickly absorb even trace amounts of lead and other heavy metals from water. The researchers showed that they could package the yeast inside hydrogel capsules to create a filter that removes lead from water. Because the yeast cells are encapsulated, they can be easily removed from the water once it’s ready to drink.“We have the hydrogel surrounding the free yeast that exists in the center, and this is porous enough to let water come in, interact with yeast as if they were freely moving in water, and then come out clean,” says Patricia Stathatou, a former postdoc at the MIT Center for Bits and Atoms, who is now a research scientist at Georgia Tech and an incoming assistant professor at Georgia Tech’s School of Chemical and Biomolecular Engineering. “The fact that the yeast themselves are bio-based, benign, and biodegradable is a significant advantage over traditional technologies.”The researchers envision that this process could be used to filter drinking water coming out of a faucet in homes, or scaled up to treat large quantities of water at treatment plants.MIT graduate student Devashish Gokhale and Stathatou are the lead authors of the study, which appears today in the journal RSC Sustainability. Patrick Doyle, the Robert T. Haslam Professor of Chemical Engineering at MIT, is the senior author of the paper, and Christos Athanasiou, an assistant professor of aerospace engineering at Georgia Tech and a former visiting scholar at MIT, is also an author.Absorbing leadThe new study builds on work that Stathatou and Athanasiou began in 2021, when Athanasiou was a visiting scholar at MIT’s Center for Bits and Atoms. That year, they calculated that waste yeast discarded from a single brewery in Boston would be enough to treat the city’s entire water supply.Through biosorption, a process that is not fully understood, yeast cells can bind to and absorb heavy metal ions, even at challenging initial concentrations below 1 part per million. The MIT team found that this process could effectively decontaminate water with low concentrations of lead. However, one key obstacle remained, which was how to remove yeast from the water after they absorb the lead.In a serendipitous coincidence, Stathatou and Athanasiou happened to present their research at the AIChE Annual Meeting in Boston in 2021, where Gokhale, a student in Doyle’s lab, was presenting his own research on using hydrogels to capture micropollutants in water. The two sets of researchers decided to join forces and explore whether the yeast-based strategy could be easier to scale up if the yeast were encapsulated in hydrogels developed by Gokhale and Doyle.“What we decided to do was make these hollow capsules — something like a multivitamin pill, but instead of filling them up with vitamins, we fill them up with yeast cells,” Gokhale says. “These capsules are porous, so the water can go into the capsules and the yeast are able to bind all of that lead, but the yeast themselves can’t escape into the water.”The capsules are made from a polymer called polyethylene glycol (PEG), which is widely used in medical applications. To form the capsules, the researchers suspend freeze-dried yeast in water, then mix them with the polymer subunits. When UV light is shone on the mixture, the polymers link together to form capsules with yeast trapped inside.Each capsule is about half a millimeter in diameter. Because the hydrogels are very thin and porous, water can easily pass through and encounter the yeast inside, while the yeast remain trapped.In this study, the researchers showed that the encapsulated yeast could remove trace lead from water just as rapidly as the unencapsulated yeast from Stathatou and Athanasiou’s original 2021 study.Scaling upLed by Athanasiou, the researchers tested the mechanical stability of the hydrogel capsules and found that the capsules and the yeast inside can withstand forces similar to those generated by water running from a faucet. They also calculated that the yeast-laden capsules should be able to withstand forces generated by flows in water treatment plants serving several hundred residences.“Lack of mechanical robustness is a common cause of failure of previous attempts to scale-up biosorption using immobilized cells; in our work we wanted to make sure that this aspect is thoroughly addressed from the very beginning to ensure scalability,” Athanasiou says.After assessing the mechanical robustness of the yeast-laden capsules, the researchers constructed a proof-of-concept packed-bed biofilter, capable of treating trace lead-contaminated water and meeting U.S. Environmental Protection Agency drinking water guidelines while operating continuously for 12 days.This process would likely consume less energy than existing physicochemical processes for removing trace inorganic compounds from water, such as precipitation and membrane filtration, the researchers say.This approach, rooted in circular economy principles, could minimize waste and environmental impact while also fostering economic opportunities within local communities. Although numerous lead contamination incidents have been reported in various locations in the United States, this approach could have an especially significant impact in low-income areas that have historically faced environmental pollution and limited access to clean water, and may not be able to afford other ways to remediate it, the researchers say.“We think that there’s an interesting environmental justice aspect to this, especially when you start with something as low-cost and sustainable as yeast, which is essentially available anywhere,” Gokhale says.The researchers are now exploring strategies for recycling and replacing the yeast once they’re used up, and trying to calculate how often that will need to occur. They also hope to investigate whether they could use feedstocks derived from biomass to make the hydrogels, instead of fossil-fuel-based polymers, and whether the yeast can be used to capture other types of contaminants.“Moving forward, this is a technology that can be evolved to target other trace contaminants of emerging concern, such as PFAS or even microplastics,” Stathatou says. “We really view this as an example with a lot of potential applications in the future.”The research was funded by the Rasikbhai L. Meswani Fellowship for Water Solutions, the MIT Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), and the Renewable Bioproducts Institute at Georgia Tech. More

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      Scientists develop an affordable sensor for lead contamination

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      Engineers at MIT, Nanytang Technological University, and several companies have developed a compact and inexpensive technology for detecting and measuring lead concentrations in water, potentially enabling a significant advance in tackling this persistent global health issue.The World Health Organization estimates that 240 million people worldwide are exposed to drinking water that contains unsafe amounts of toxic lead, which can affect brain development in children, cause birth defects, and produce a variety of neurological, cardiac, and other damaging effects. In the United States alone, an estimated 10 million households still get drinking water delivered through lead pipes.“It’s an unaddressed public health crisis that leads to over 1 million deaths annually,” says Jia Xu Brian Sia, an MIT postdoc and the senior author of the paper describing the new technology.But testing for lead in water requires expensive, cumbersome equipment and typically requires days to get results. Or, it uses simple test strips that simply reveal a yes-or-no answer about the presence of lead but no information about its concentration. Current EPA regulations require drinking water to contain no more that 15 parts per billion of lead, a concentration so low it is difficult to detect.The new system, which could be ready for commercial deployment within two or three years, could detect lead concentrations as low as 1 part per billion, with high accuracy, using a simple chip-based detector housed in a handheld device. The technology gives nearly instant quantitative measurements and requires just a droplet of water.The findings are described in a paper appearing today in the journal Nature Communications, by Sia, MIT graduate student and lead author Luigi Ranno, Professor Juejun Hu, and 12 others at MIT and other institutions in academia and industry.The team set out to find a simple detection method based on the use of photonic chips, which use light to perform measurements. The challenging part was finding a way to attach to the photonic chip surface certain ring-shaped molecules known as crown ethers, which can capture specific ions such as lead. After years of effort, they were able to achieve that attachment via a chemical process known as Fischer esterification. “That is one of the essential breakthroughs we have made in this technology,” Sia says.In testing the new chip, the researchers showed that it can detect lead in water at concentrations as low as one part per billion. At much higher concentrations, which may be relevant for testing environmental contamination such as mine tailings, the accuracy is within 4 percent.The device works in water with varying levels of acidity, ranging from pH values of 6 to 8, “which covers most environmental samples,” Sia says. They have tested the device with seawater as well as tap water, and verified the accuracy of the measurements.In order to achieve such levels of accuracy, current testing requires a device called an inductive coupled plasma mass spectrometer. “These setups can be big and expensive,” Sia says. The sample processing can take days and requires experienced technical personnel.While the new chip system they developed is “the core part of the innovation,” Ranno says, further work will be needed to develop this into an integrated, handheld device for practical use. “For making an actual product, you would need to package it into a usable form factor,” he explains. This would involve having a small chip-based laser coupled to the photonic chip. “It’s a matter of mechanical design, some optical design, some chemistry, and figuring out the supply chain,” he says. While that takes time, he says, the underlying concepts are straightforward.The system can be adapted to detect other similar contaminants in water, including cadmium, copper, lithium, barium, cesium, and radium, Ranno says. The device could be used with simple cartridges that can be swapped out to detect different elements, each using slightly different crown ethers that can bind to a specific ion.“There’s this problem that people don’t measure their water enough, especially in the developing countries,” Ranno says. “And that’s because they need to collect the water, prepare the sample, and bring it to these huge instruments that are extremely expensive.” Instead, “having this handheld device, something compact that even untrained personnel can just bring to the source for on-site monitoring, at low costs,” could make regular, ongoing widespread testing feasible.Hu, who is the John F. Elliott Professor of Materials Science and Engineering, says, “I’m hoping this will be quickly implemented, so we can benefit human society. This is a good example of a technology coming from a lab innovation where it may actually make a very tangible impact on society, which is of course very fulfilling.”“If this study can be extended to simultaneous detection of multiple metal elements, especially the presently concerning radioactive elements, its potential would be immense,” says Hou Wang, an associate professor of environmental science and engineering at Hunan University in China, who was not associated with this work.Wang adds, “This research has engineered a sensor capable of instantaneously detecting lead concentration in water. This can be utilized in real-time to monitor the lead pollution concentration in wastewater discharged from industries such as battery manufacturing and lead smelting, facilitating the establishment of industrial wastewater monitoring systems. I think the innovative aspects and developmental potential of this research are quite commendable.”Wang Qian, a principal research scientist at the Institute of Materials Research in Singapore, who also was not affiliated with this work, says, “The ability for the pervasive, portable, and quantitative detection of lead has proved to be challenging primarily due to cost concerns. This work demonstrates the potential to do so in a highly integrated form factor and is compatible with large-scale, low-cost manufacturing.”The team included researchers at MIT, at Nanyang Technological University and Temasek Laboratories in Singapore, at the University of Southampton in the U.K., and at companies Fingate Technologies, in Singapore, and Vulcan Photonics, headquartered in Malaysia. The work used facilities at MIT.nano, the Harvard University Center for Nanoscale Systems, NTU’s Center for Micro- and Nano-Electronics, and the Nanyang Nanofabrication Center. More

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      Exploring frontiers of mechanical engineering

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      From cutting-edge robotics, design, and bioengineering to sustainable energy solutions, ocean engineering, nanotechnology, and innovative materials science, MechE students and their advisors are doing incredibly innovative work. The graduate students highlighted here represent a snapshot of the great work in progress this spring across the Department of Mechanical Engineering, and demonstrate the ways the future of this field is as limitless as the imaginations of its practitioners.Democratizing design through AILyle RegenwetterHometown: Champaign, IllinoisAdvisor: Assistant Professor Faez AhmedInterests: Food, climbing, skiing, soccer, tennis, cookingLyle Regenwetter finds excitement in the prospect of generative AI to “democratize” design and enable inexperienced designers to tackle complex design problems. His research explores new training methods through which generative AI models can be taught to implicitly obey design constraints and synthesize higher-performing designs. Knowing that prospective designers often have an intimate knowledge of the needs of users, but may otherwise lack the technical training to create solutions, Regenwetter also develops human-AI collaborative tools that allow AI models to interact and support designers in popular CAD software and real design problems. Solving a whale of a problem Loïcka BailleHometown: L’Escale, FranceAdvisor: Daniel ZitterbartInterests: Being outdoors — scuba diving, spelunking, or climbing. Sailing on the Charles River, martial arts classes, and playing volleyballLoïcka Baille’s research focuses on developing remote sensing technologies to study and protect marine life. Her main project revolves around improving onboard whale detection technology to prevent vessel strikes, with a special focus on protecting North Atlantic right whales. Baille is also involved in an ongoing study of Emperor penguins. Her team visits Antarctica annually to tag penguins and gather data to enhance their understanding of penguin population dynamics and draw conclusions regarding the overall health of the ecosystem.Water, water anywhereCarlos Díaz-MarínHometown: San José, Costa RicaAdvisor: Professor Gang Chen | Former Advisor: Professor Evelyn WangInterests: New England hiking, biking, and dancingCarlos Díaz-Marín designs and synthesizes inexpensive salt-polymer materials that can capture large amounts of humidity from the air. He aims to change the way we generate potable water from the air, even in arid conditions. In addition to water generation, these salt-polymer materials can also be used as thermal batteries, capable of storing and reusing heat. Beyond the scientific applications, Díaz-Marín is excited to continue doing research that can have big social impacts, and that finds and explains new physical phenomena. As a LatinX person, Díaz-Marín is also driven to help increase diversity in STEM.Scalable fabrication of nano-architected materialsSomayajulu DhulipalaHometown: Hyderabad, IndiaAdvisor: Assistant Professor Carlos PortelaInterests: Space exploration, taekwondo, meditation.Somayajulu Dhulipala works on developing lightweight materials with tunable mechanical properties. He is currently working on methods for the scalable fabrication of nano-architected materials and predicting their mechanical properties. The ability to fine-tune the mechanical properties of specific materials brings versatility and adaptability, making these materials suitable for a wide range of applications across multiple industries. While the research applications are quite diverse, Dhulipala is passionate about making space habitable for humanity, a crucial step toward becoming a spacefaring civilization.Ingestible health-care devicesJimmy McRaeHometown: Woburn, MassachusettsAdvisor: Associate Professor Giovani TraversoInterests: Anything basketball-related: playing, watching, going to games, organizing hometown tournaments Jimmy McRae aims to drastically improve diagnostic and therapeutic capabilities through noninvasive health-care technologies. His research focuses on leveraging materials, mechanics, embedded systems, and microfabrication to develop novel ingestible electronic and mechatronic devices. This ranges from ingestible electroceutical capsules that modulate hunger-regulating hormones to devices capable of continuous ultralong monitoring and remotely triggerable actuations from within the stomach. The principles that guide McRae’s work to develop devices that function in extreme environments can be applied far beyond the gastrointestinal tract, with applications for outer space, the ocean, and more.Freestyle BMX meets machine learningEva NatesHometown: Narberth, Pennsylvania Advisor: Professor Peko HosoiInterests: Rowing, running, biking, hiking, bakingEva Nates is working with the Australian Cycling Team to create a tool to classify Bicycle Motocross Freestyle (BMX FS) tricks. She uses a singular value decomposition method to conduct a principal component analysis of the time-dependent point-tracking data of an athlete and their bike during a run to classify each trick. The 2024 Olympic team hopes to incorporate this tool in their training workflow, and Nates worked alongside the team at their facilities on the Gold Coast of Australia during MIT’s Independent Activities Period in January.Augmenting Astronauts with Wearable Limbs Erik BallesterosHometown: Spring, TexasAdvisor: Professor Harry AsadaInterests: Cosplay, Star Wars, Lego bricksErik Ballesteros’s research seeks to support astronauts who are conducting planetary extravehicular activities through the use of supernumerary robotic limbs (SuperLimbs). His work is tailored toward design and control manifestation to assist astronauts with post-fall recovery, human-leader/robot-follower quadruped locomotion, and coordinated manipulation between the SuperLimbs and the astronaut to perform tasks like excavation and sample handling.This article appeared in the Spring 2024 edition of the Department of Mechanical Engineering’s magazine, MechE Connects.  More

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      MADMEC winner creates “temporary tattoos” for T-shirts

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      Have you ever gotten a free T-shirt at an event that you never wear? What about a music or sports-themed shirt you wear to one event and then lose interest in entirely? Such one-off T-shirts — and the waste and pollution associated with them — are an unfortunately common part of our society.

      But what if you could change the designs on shirts after each use? The winners of this year’s MADMEC competition developed biodegradable “temporary tattoos” for T-shirts to make one-wear clothing more sustainable.

      Members of the winning team, called Me-Shirts, got their inspiration from the MADMEC event itself, which ordinarily makes a different T-shirt each year.

      “If you think about all the textile waste that’s produced for all these shirts, it’s insane,” team member and PhD candidate Isabella Caruso said in the winning presentation. “The main markets we are trying to address are for one-time T-shirts and custom T-shirts.”

      The problem is a big one. According to the team, the custom T-shirt market is a $4.3 billion industry. That doesn’t include trends like fast fashion that contribute to the 17 million tons of textile waste produced each year.

      “Our proposed solution is a temporary shirt tattoo made from biodegradable, nontoxic materials,” Caruso explained. “We wanted designs that are fully removable through washing, so that you can wear your T-shirt for your one-time event and then get a nice white T-shirt back afterward.”

      The team’s scalable design process mixes three simple ingredients: potato starch, glycerin, and water. The design can be imprinted on the shirt temporarily through ironing.

      The Me-Shirt team, which earned $10,000 with the win, plans to continue exploring material combinations to make the design more flexible and easier for people to apply at home. Future iterations could allow users to decide if they want the design to stay on the shirt during washes based on the settings of the washing machine.

      Hosted by MIT’s Department of Materials Science and Engineering (DMSE), the competition was the culmination of team projects that began in the fall and included a series of design challenges throughout the semester. Each team received guidance, access to equipment and labs, and up to $1,000 in funding to build and test their prototypes.

      “The main goal is that they gained some confidence in their ability to design and build devices and platforms that are different from their normal experiences,” Mike Tarkanian, a senior lecturer in DMSE and coordinator of MADMEC, said at the event. “If it’s a departure from their normal research and coursework activities that’s a win, I think, to make them better engineers.”

      The second-place, $6,000 prize went to Alkalyne, which is creating a carbon-neutral polymer for petrochemical production. The company is developing approaches for using electricity and inorganic carbon to generate a high-energy hydrocarbon precursor. If developed using renewable energy, the approach could be used to achieve carbon negative petrochemical production.

      “A lot of our research, and a lot of the research around MIT in general, has to do with sustainability, so we wanted to try an angle that we think looks promising but doesn’t seem to be investigated enough,” PhD candidate Christopher Mallia explained.

      The third-place prize went to Microbeco, which is exploring the use of microbial fuel cells for continuous water quality monitoring. Microbes have been proposed as a way to detect and measure contaminants in water for decades, but the team believes the varying responses of microbes to different contaminants has limited the effectiveness of the approach.

      To overcome that problem, the team is working to isolate microbial strains that respond more regularly to specific contaminants.

      Overall, Tarkanian believes this year’s program was a success not only because of the final results presented at the competition, but because of the experience the students got along the way using equipment like laser cutters, 3D printers, and soldering irons. Many participants said they had never used that type of equipment before. They also said by working to build physical prototypes, the program helped make their coursework come to life.

      “It was a chance to try something new by applying my skills to a different environment,” PhD candidate Zachary Adams said. “I can see a lot of the concepts I learn in my classes through this work.” More