More stories

  • in

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

    Rain can freefall at speeds of up to 25 miles per hour. If the droplets land in a puddle or pond, they can form a crown-like splash that, with enough force, can dislodge any surface particles and launch them into the air.Now MIT scientists have taken high-speed videos of droplets splashing into a deep pool, to track how the fluid evolves, above and below the water line, frame by millisecond frame. Their work could help to predict how spashing droplets, such as from rainstorms and irrigation systems, may impact watery surfaces and aerosolize surface particles, such as pollen on puddles or pesticides in agricultural runoff.The team carried out experiments in which they dispensed water droplets of various sizes and from various heights into a pool of water. Using high-speed imaging, they measured how the liquid pool deformed as the impacting droplet hit the pool’s surface.Across all their experiments, they observed a common splash evolution: As a droplet hit the pool, it pushed down below the surface to form a “crater,” or cavity. At nearly the same time, a wall of liquid rose above the surface, forming a crown. Interestingly, the team observed that small, secondary droplets were ejected from the crown before the crown reached its maximum height. This entire evolution happens in a fraction of a second.

    “This cylinder-like wall of rising liquid, and how it evolves in time and space, is at the heart of everything,” Lydia Bourouiba says. GIF has been edited down to 5 frames per second.

    Image: Courtesy of the researchers; edited by MIT News

    Previous item
    Next item

    Scientists have caught snapshots of droplet splashes in the past, such as the famous “Milk Drop Coronet” — a photo of a drop of milk in mid-splash, taken by the late MIT professor Harold “Doc” Edgerton, who invented a photographic technique to capture quickly moving objects.The new work represents the first time scientists have used such high-speed images to model the entire splash dynamics of a droplet in a deep pool, combining what happens both above and below the surface. The team has used the imaging to gather new data central to build a mathematical model that predicts how a droplet’s shape will morph and merge as it hits a pool’s surface. They plan to use the model as a baseline to explore to what extent a splashing droplet might drag up and launch particles from the water pool.“Impacts of drops on liquid layers are ubiquitous,” says study author Lydia Bourouiba, a professor in the MIT departments of Civil and Environmental Engineering and Mechanical Engineering, and a core member of the Institute for Medical Engineering and Science (IMES). “Such impacts can produce myriads of secondary droplets that could act as carriers for pathogens, particles, or microbes that are on the surface of impacted pools or contaminated water bodies. This work is key in enabling prediction of droplet size distributions, and potentially also what such drops can carry with them.”Bourouiba and her mentees have published their results in the Journal of Fluid Mechanics. MIT co-authors include former graduate student Raj Dandekar PhD ’22, postdoc (Eric) Naijian Shen, and student mentee Boris Naar.Above and belowAt MIT, Bourouiba heads up the Fluid Dynamics of Disease Transmission Laboratory, part of the Fluids and Health Network, where she and her team explore the fundamental physics of fluids and droplets in a range of environmental, energy, and health contexts, including disease transmission. For their new study, the team looked to better understand how droplets impact a deep pool — a seemingly simple phenomenon that nevertheless has been tricky to precisely capture and characterize.Bourouiba notes that there have been recent breakthroughs in modeling the evolution of a splashing droplet below a pool’s surface. As a droplet hits a pool of water, it breaks through the surface and drags air down through the pool to create a short-lived crater. Until now, scientists have focused on the evolution of this underwater cavity, mainly for applications in energy harvesting. What happens above the water, and how a droplet’s crown-like shape evolves with the cavity below, remained less understood.“The descriptions and understanding of what happens below the surface, and above, have remained very much divorced,” says Bourouiba, who believes such an understanding can help to predict how droplets launch and spread chemicals, particles, and microbes into the air.Splash in 3DTo study the coupled dynamics between a droplet’s cavity and crown, the team set up an experiment to dispense water droplets into a deep pool. For the purposes of their study, the researchers considered a deep pool to be a body of water that is deep enough that a splashing droplet would remain far away from the pool’s bottom. In these terms, they found that a pool with a depth of at least 20 centimeters was sufficient for their experiments.They varied each droplet’s size, with an average diameter of about 5 millimeters. They also dispensed droplets from various heights, causing the droplets to hit the pool’s surface at different speeds, which on average was about 5 meters per second. The overall dynamics, Bourouiba says, should be similar to what occurs on the surface of a puddle or pond during an average rainstorm.“This is capturing the speed at which raindrops fall,” she says. “These wouldn’t be very small, misty drops. This would be rainstorm drops for which one needs an umbrella.”Using high-speed imaging techniques inspired by Edgerton’s pioneering photography, the team captured videos of pool-splashing droplets, at rates of up to 12,500 frames per second. They then applied in-house imaging processing methods to extract key measurements from the image sequences, such as the changing width and depth of the underwater cavity, and the evolving diameter and height of the rising crown. The researchers also captured especially tricky measurements, of the crown’s wall thickness profile and inner flow — the cylinder that rises out of the pool, just before it forms a rim and points that are characteristic of a crown.“This cylinder-like wall of rising liquid, and how it evolves in time and space, is at the heart of everything,” Bourouiba says. “It’s what connects the fluid from the pool to what will go into the rim and then be ejected into the air through smaller, secondary droplets.”The researchers worked the image data into a set of “evolution equations,” or a mathematical model that relates the various properties of an impacting droplet, such as the width of its cavity and the thickness and speed profiles of its crown wall, and how these properties change over time, given a droplet’s starting size and impact speed.“We now have a closed-form mathematical expression that people can use to see how all these quantities of a splashing droplet change over space and time,” says co-author Shen, who plans, with Bourouiba, to apply the new model to the behavior of secondary droplets and understanding how a splash end-up dispersing particles such as pathogens and pesticides. “This opens up the possibility to study all these problems of splash in 3D, with self-contained closed-formed equations, which was not possible before.”This research was supported, in part, by the Department of Agriculture-National Institute of Food and Agriculture Specialty Crop Research Initiative; the Richard and Susan Smith Family Foundation; the National Science Foundation; the Centers for Disease Control and Prevention-National Institute for Occupational Safety and Health; Inditex; and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health. More

  • in

    Pivot Bio is using microbial nitrogen to make agriculture more sustainable

    The Haber-Bosch process, which converts atmospheric nitrogen to make ammonia fertilizer, revolutionized agriculture and helped feed the world’s growing population, but it also created huge environmental problems. It is one of the most energy-intensive chemical processes in the world, responsible for 1-2 percent of global energy consumption. It also releases nitrous oxide, a potent greenhouse gas that harms the ozone layer. Excess nitrogen also routinely runs off farms into waterways, harming marine life and polluting groundwater.In place of synthetic fertilizer, Pivot Bio has engineered nitrogen-producing microbes to make farming more sustainable. The company, which was co-founded by Professor Chris Voigt, Karsten Temme, and Alvin Tamsir, has engineered its microbes to grow on plant roots, where they feed on the root’s sugars and precisely deliver nitrogen in return.Pivot’s microbial colonies grow with the plant and produce more nitrogen at exactly the time the plant needs it, minimizing nitrogen runoff.“The way we have delivered nutrients to support plant growth historically is fertilizer, but that’s an inefficient way to get all the nutrients you need,” says Temme, Pivot’s chief innovation officer. “We have the ability now to help farmers be more efficient and productive with microbes.”Farmers can replace up to 40 pounds per acre of traditional nitrogen with Pivot’s product, which amounts to about a quarter of the total nitrogen needed for a crop like corn.Pivot’s products are already being used to grow corn, wheat, barley, oats, and other grains across millions of acres of American farmland, eliminating hundreds of thousands of tons of CO2 equivalent in the process. The company’s impact is even more striking given its unlikely origins, which trace back to one of the most challenging times of Voigt’s career.A Pivot from despairThe beginning of every faculty member’s career can be a sink-or-swim moment, and by Voigt’s own account, he was drowning. As a freshly minted assistant professor at the University of California at San Francisco, Voigt was struggling to stand up his lab, attract funding, and get experiments started.Around 2008, Voigt joined a research group out of the University of California at Berkeley that was writing a grant proposal focused on photovoltaic materials. His initial role was minor, but a senior researcher pulled out of the group a week before the proposal had to be submitted, so Voigt stepped up.“I said ‘I’ll finish this section in a week,’” Voigt recalls. “It was my big chance.”For the proposal, Voigt detailed an ambitious plan to rearrange the genetics of biologic photosynthetic systems to make them more efficient. He barely submitted it in time.A few months went by, then the proposal reviews finally came back. Voigt hurried to the meeting with some of the most senior researchers at UC Berkeley to discuss the responses.“My part of the proposal got completely slammed,” Voigt says. “There were something like 15 reviews on it — they were longer than the actual grant — and it’s just one after another tearing into my proposal. All the most famous people are in this meeting, future energy secretaries, future leaders of the university, and it was totally embarrassing. After that meeting, I was considering leaving academia.”A few discouraging months later, Voigt got a call from Paul Ludden, the dean of the School of Science at UC Berkeley. He wanted to talk.“As I walk into Paul’s office, he’s reading my proposal,” Voigt recalls. “He sits me down and says, ‘Everybody’s telling me how terrible this is.’ I’m thinking, ‘Oh my God.’ But then he says, ‘I think there’s something here. Your idea is good, you just picked the wrong system.’”Ludden went on to explain to Voigt that he should apply his gene-swapping idea to nitrogen fixation. He even offered to send Voigt a postdoc from his lab, Dehua Zhao, to help. Voigt paired Zhao with Temme, and sure enough, the resulting 2011 paper of their work was well-received by the nitrogen fixation community.“Nitrogen fixation has been a holy grail for scientists, agronomists, and farmers for almost a century, ever since somebody discovered the first microbe that can fix nitrogen for legumes like soybeans,” Temme says. “Everybody always said that someday we’ll be able to do this for the cereal crops. The excitement with Pivot was this is the first time that technology became accessible.”Voigt had moved to MIT in 2010. When the paper came out, he founded Pivot Bio with Temme and another Berkeley researcher, Alvin Tamsir. Since then, Voigt, who is the Daniel I.C. Wang Professor at MIT and the head of the Department of Biological Engineering, has continued collaborating with Pivot on things like increasing nitrogen production, making strains more stable, and making them inducible to different signals from the plant. Pivot has licensed technology from MIT, and the research has also received support from MIT’s Abdul Latif Jameel Water and Food Systems Lab (J-WAFS).Pivot’s first goals were to gain regulatory approval and prove themselves in the marketplace. To gain approval in the U.S., Pivot’s team focused on using DNA from within the same organism rather than bringing in totally new DNA, which simplified the approval process. It also partnered with independent corn seed dealers to get its product to farms. Early deployments occurred in 2019.Farmers apply Pivot’s product at planting, either as a liquid that gets sprayed on the soil or as a dry powder that is rehydrated and applied to the seeds as a coating. The microbes live on the surface of the growing root system, eating plant sugars and releasing nitrogen throughout the plant’s life cycle.“Today, our microbes colonize just a fraction of the total sugars provided by the plant,” Temme explains. “They’re also sharing ammonia with the plant, and all of those things are just a portion of what’s possible technically. Our team is always trying to figure out how to make those microbes more efficient at getting the energy they need to grow or at fixing nitrogen and sharing it with the crop.”In 2023, Pivot started the N-Ovator program to connect companies with growers who practice sustainable farming using Pivot’s microbial nitrogen. Through the program, companies buy nitrogen credits and farmers can get paid by verifying their practices. The program was named one of the Inventions of the Year by Time Magazine last year and has paid out millions of dollars to farmers to date.Microbial nitrogen and beyondPivot is currently selling to farmers across the U.S. and working with smallholder farmers in Kenya. It’s also hoping to gain approval for its microbial solution in Brazil and Canada, which it hopes will be its next markets.”How do we get the economics to make sense for everybody — the farmers, our partners, and the company?” Temme says of Pivot’s mission. “Because this truly can be a deflationary technology that upends the very expensive traditional way of making fertilizer.”Pivot’s team is also extending the product to cotton, and Temme says microbes can be a nitrogen source for any type of plant on the planet. Further down the line, the company believes it can help farmers with other nutrients essential to help their crops grow.“Now that we’ve established our technology, how can Pivot help farmers overcome all the other limitations they face with crop nutrients to maximize yields?” Temme asks. “That really starts to change the way a farmer thinks about managing the entire acre from a price, productivity, and sustainability perspective.” More

  • in

    Coffee fix: MIT students decode the science behind the perfect cup

    Elaine Jutamulia ’24 took a sip of coffee with a few drops of anise extract. It was her second try.“What do you think?” asked Omar Orozco, standing at a lab table in MIT’s Breakerspace, surrounded by filters, brewing pots, and other coffee paraphernalia.“I think when I first tried it, it was still pretty bitter,” Jutamulia said thoughtfully. “But I think now that it’s steeped for a little bit — it took out some of the bitterness.”Jutamulia and current MIT senior Orozco were part of class 3.000 (Coffee Matters: Using the Breakerspace to Make the Perfect Cup), a new MIT course that debuted in spring 2024. The class combines lectures on chemistry and the science of coffee with hands-on experimentation and group projects. Their project explored how additives such as anise, salt, and chili oil influence coffee extraction — the process of dissolving flavor compounds from ground coffee into water — to improve taste and correct common brewing errors.Alongside tasting, they used an infrared spectrometer to identify the chemical compounds in their coffee samples that contribute to flavor. Does anise make bitter coffee smoother? Could chili oil balance the taste?“Generally speaking, if we could make a recommendation, that’s what we’re trying to find,” Orozco said.A three-unit “discovery class” designed to help first-year students explore majors, 3.000 was widely popular, enrolling more than 50 students. Its success was driven by the beverage at its core and the class’s hands-on approach, which pushes students to ask and answer questions they might not have otherwise.For aeronautics and astronautics majors Gabi McDonald and McKenzie Dinesen, coffee was the draw, but the class encouraged them to experiment and think in new ways. “It’s easy to drop people like us in, who love coffee, and, ‘Oh my gosh, there’s this class where we can go make coffee half the time and try all different kinds of things?’” McDonald says.Percolating knowledgeThe class pairs weekly lectures on topics such as coffee chemistry, the anatomy and composition of a coffee bean, the effects of roasting, and the brewing process with tasting sessions — students sample coffee brewed from different beans, roasts, and grinds. In the MIT Breakerspace, a new space on campus conceived and managed by the Department of Materials Science and Engineering (DMSE), students use equipment such as a digital optical microscope to examine ground coffee particles and a scanning electron microscope, which shoots beams of electrons at samples to reveal cross-sections of beans in stunning detail.Once students learn to operate instruments for guided tasks, they form groups and design their own projects.“The driver for those projects is some question they have about coffee raised by one of the lectures or the tasting sessions, or just something they’ve always wanted to know,” says DMSE Professor Jeffrey Grossman, who designed and teaches the class. “Then they’ll use one or more of these pieces of equipment to shed some light on it.”Grossman traces the origins of the class to his initial vision for the Breakerspace, a laboratory for materials analysis and lounge for MIT undergraduates. Opened in November 2023, the space gives students hands-on experience with materials science and engineering, an interdisciplinary field combining chemistry, physics, and engineering to probe the composition and structure of materials.“The world is made of stuff, and these are the tools to understand that stuff and bring it to life,” says Grossman. So he envisioned a class that would give students an “exploratory, inspiring nudge.”“Then the question wasn’t the pedagogy, it was, ‘What’s the hook?’ In materials science, there are a lot of directions you could go, but if you have one that inspires people because they know it and maybe like it already, then that’s exciting.”Cup of ambitionThat hook, of course, was coffee, the second-most-consumed beverage after water. It captured students’ imagination and motivated them to push boundaries.Orozco brought a fair amount of coffee knowledge to the class. In 2023, he taught in Mexico through the MISTI Global Teaching Labs program, where he toured several coffee farms and acquired a deeper knowledge of the beverage. He learned, for example, that black coffee, contrary to general American opinion, isn’t naturally bitter; bitterness arises from certain compounds that develop during the roasting process.“If you properly brew it with the right beans, it actually tastes good,” says Orozco, a humanities and engineering major. A year later, in 3.000, he expanded his understanding of making a good brew, particularly through the group project with Jutamulia and other students to fix bad coffee.The group prepared a control sample of “perfectly brewed” coffee — based on taste, coffee-to-water ratio, and other standards covered in class — alongside coffee that was under-extracted and over-extracted. Under-extracted coffee, made with water that isn’t hot enough or brewed for too short a time, tastes sharp or sour. Over-extracted coffee, brewed with too much coffee or for too long, tastes bitter.Those coffee samples got additives and were analyzed using Fourier Transform Infrared (FTIR) spectroscopy, measuring how coffee absorbed infrared light to identify flavor-related compounds. Jutamulia examined FTIR readings taken from a sample with lime juice to see how the citric acid influenced its chemical profile.“Can we find any correlation between what we saw and the existing known measurements of citric acid?” asks Jutamulia, who studied computation and cognition at MIT, graduating last May.Another group dove into coffee storage, questioning why conventional wisdom advises against freezing.“We just wondered why that’s the case,” says electrical engineering and computer science major Noah Wiley, a coffee enthusiast with his own espresso machine.The team compared methods like freezing brewed coffee, frozen coffee grounds, and whole beans ground after freezing, evaluating their impact on flavor and chemical composition.“Then we’re going to see which ones taste good,” says Wiley. The team used a class coffee review sheet to record attributes like acidity, bitterness, sweetness, and overall flavor, pairing the results with FTIR analysis to determine how storage affected taste.Wiley acknowledged that “good” is subjective. “Sometimes there’s a group consensus. I think people like fuller coffee, not watery,” he says.Other student projects compared caffeine levels in different coffee types, analyzed the effect of microwaving coffee on its chemical composition and flavor, and investigated the differences between authentic and counterfeit coffee beans.“We gave the students some papers to look at in case they were interested,” says Justin Lavallee, Breakerspace manager and co-teacher of the class. “But mostly we told them to focus on something they wanted to learn more about.”Drip, drip, dripBeyond answering specific questions about coffee, both students and teachers gained deeper insights into the beverage.“Coffee is a complicated material. There are thousands of molecules in the beans, which change as you roast and extract them,” says Grossman. “The number of ways you can engineer this collection of molecules — it’s profound, ranging from where and how the coffee’s grown to how the cherries are then treated to get the beans to how the beans are roasted and ground to the brewing method you use.”Dinesen learned firsthand, discovering, for example, that darker roasts have less caffeine than lighter roasts, puncturing a common misconception. “You can vary coffee so much — just with the roast of the bean, the size of the ground,” she says. “It’s so easily manipulatable, if that’s a word.”In addition to learning about the science and chemistry behind coffee, Dinesen and McDonald gained new brewing techniques, like using a pour-over cone. The pair even incorporated coffee making and testing into their study routine, brewing coffee while tackling problem sets for another class.“I would put my pour-over cone in my backpack with a Ziploc bag full of grounds, and we would go to the Student Center and pull out the cone, a filter, and the coffee grounds,” McDonald says. “And then we would make pour-overs while doing a P-set. We tested different amounts of water, too. It was fun.”Tony Chen, a materials science and engineering major, reflected on the 3.000’s title — “Using the Breakerspace to Make the Perfect Cup” — and whether making a perfect cup is possible. “I don’t think there’s one perfect cup because each person has their own preferences. I don’t think I’ve gotten to mine yet,” he says.Enthusiasm for coffee’s complexity and the discovery process was exactly what Grossman hoped to inspire in his students. “The best part for me was also just seeing them developing their own sense of curiosity,” he says.He recalled a moment early in the class when students, after being given a demo of the optical microscope, saw the surface texture of a magnified coffee bean, the mottled shades of color, and the honeycomb-like pattern of tiny irregular cells.“They’re like, ‘Wait a second. What if we add hot water to the grounds while it’s under the microscope? Would we see the extraction?’ So, they got hot water and some ground coffee beans, and lo and behold, it looked different. They could see the extraction right there,” Grossman says. “It’s like they have an idea that’s inspired by the learning, and they go and try it. I saw that happen many, many times throughout the semester.” More

  • in

    Liquid on Mars was not necessarily all water

    Dry river channels and lake beds on Mars point to the long-ago presence of a liquid on the planet’s surface, and the minerals observed from orbit and from landers seem to many to prove that the liquid was ordinary water. Not so fast, the authors of a new Perspectives article in Nature Geoscience suggest. Water is only one of two possible liquids under what are thought to be the conditions present on ancient Mars. The other is liquid carbon dioxide (CO2), and it may actually have been easier for CO2 in the atmosphere to condense into a liquid under those conditions than for water ice to melt. While others have suggested that liquid CO2 (LCO2) might be the source of some of the river channels seen on Mars, the mineral evidence has seemed to point uniquely to water. However, the new paper cites recent studies of carbon sequestration, the process of burying liquefied CO2 recovered from Earth’s atmosphere deep in underground caverns, which show that similar mineral alteration can occur in liquid CO2 as in water, sometimes even more rapidly.The new paper is led by Michael Hecht, principal investigator of the MOXIE instrument aboard the NASA Mars Rover Perseverance. Hecht, a research scientist at MIT’s Haystack Observatory and a former associate director, says, “Understanding how sufficient liquid water was able to flow on early Mars to explain the morphology and mineralogy we see today is probably the greatest unsettled question of Mars science. There is likely no one right answer, and we are merely suggesting another possible piece of the puzzle.”In the paper, the authors discuss the compatibility of their proposal with current knowledge of Martian atmospheric content and implications for Mars surface mineralogy. They also explore the latest carbon sequestration research and conclude that “LCO2–mineral reactions are consistent with the predominant Mars alteration products: carbonates, phyllosilicates, and sulfates.” The argument for the probable existence of liquid CO2 on the Martian surface is not an all-or-nothing scenario; either liquid CO2, liquid water, or a combination may have brought about such geomorphological and mineralogical evidence for a liquid Mars.Three plausible cases for liquid CO2 on the Martian surface are proposed and discussed: stable surface liquid, basal melting under CO2 ice, and subsurface reservoirs. The likelihood of each depends on the actual inventory of CO2 at the time, as well as the temperature conditions on the surface.The authors acknowledge that the tested sequestration conditions, where the liquid CO2 is above room temperature at pressures of tens of atmospheres, are very different from the cold, relatively low-pressure conditions that might have produced liquid CO2 on early Mars. They call for further laboratory investigations under more realistic conditions to test whether the same chemical reactions occur.Hecht explains, “It’s difficult to say how likely it is that this speculation about early Mars is actually true. What we can say, and we are saying, is that the likelihood is high enough that the possibility should not be ignored.”  More

  • in

    An inflatable gastric balloon could help people lose weight

    Gastric balloons — silicone balloons filled with air or saline and placed in the stomach — can help people lose weight by making them feel too full to overeat. However, this effect eventually can wear off as the stomach becomes used to the sensation of fullness.To overcome that limitation, MIT engineers have designed a new type of gastric balloon that can be inflated and deflated as needed. In an animal study, they showed that inflating the balloon before a meal caused the animals to reduce their food intake by 60 percent.This type of intervention could offer an alternative for people who don’t want to undergo more invasive treatments such as gastric bypass surgery, or people who don’t respond well to weight-loss drugs, the researchers say.“The basic concept is we can have this balloon that is dynamic, so it would be inflated right before a meal and then you wouldn’t feel hungry. Then it would be deflated in between meals,” says Giovanni Traverso, an associate professor of mechanical engineering at MIT, a gastroenterologist at Brigham and Women’s Hospital, and the senior author of the study.Neil Zixun Jia, who received a PhD from MIT in 2023, is the lead author of the paper, which appears today in the journal Device.An inflatable balloonGastric balloons filled with saline are currently approved for use in the United States. These balloons stimulate a sense of fullness in the stomach, and studies have shown that they work well, but the benefits are often temporary.“Gastric balloons do work initially. Historically, what has been seen is that the balloon is associated with weight loss. But then in general, the weight gain resumes the same trajectory,” Traverso says. “What we reasoned was perhaps if we had a system that simulates that fullness in a transient way, meaning right before a meal, that could be a way of inducing weight loss.”To achieve a longer-lasting effect in patients, the researchers set out to design a device that could expand and contract on demand. They created two prototypes: One is a traditional balloon that inflates and deflates, and the other is a mechanical device with four arms that expand outward, pushing out an elastic polymer shell that presses on the stomach wall.In animal tests, the researchers found that the mechanical-arm device could effectively expand to fill the stomach, but they ended up deciding to pursue the balloon option instead.“Our sense was that the balloon probably distributed the force better, and down the line, if you have balloon that is applying the pressure, that is probably a safer approach in the long run,” Traverso says.The researchers’ new balloon is similar to a traditional gastric balloon, but it is inserted into the stomach through an incision in the abdominal wall. The balloon is connected to an external controller that can be attached to the skin and contains a pump that inflates and deflates the balloon when needed. Inserting this device would be similar to the procedure used to place a feeding tube into a patient’s stomach, which is commonly done for people who are unable to eat or drink.“If people, for example, are unable to swallow, they receive food through a tube like this. We know that we can keep tubes in for years, so there is already precedent for other systems that can stay in the body for a very long time. That gives us some confidence in the longer-term compatibility of this system,” Traverso says.Reduced food intakeIn tests in animals, the researchers found that inflating the balloon before meals led to a 60 percent reduction in the amount of food consumed. These studies were done over the course of a month, but the researchers now plan to do longer-term studies to see if this reduction leads to weight loss.“The deployment for traditional gastric balloons is usually six months, if not more, and only then you will see good amount of weight loss. We will have to evaluate our device in a similar or longer time span to prove it really works better,” Jia says.If developed for use in humans, the new gastric balloon could offer an alternative to existing obesity treatments. Other treatments for obesity include gastric bypass surgery, “stomach stapling” (a surgical procedure in which the stomach capacity is reduced), and drugs including GLP-1 receptor agonists such as semaglutide.The gastric balloon could be an option for patients who are not good candidates for surgery or don’t respond well to weight-loss drugs, Traverso says.“For certain patients who are higher-risk, who cannot undergo surgery, or did not tolerate the medication or had some other contraindication, there are limited options,” he says. “Traditional gastric balloons are still being used, but they come with a caveat that eventually the weight loss can plateau, so this is a way of trying to address that fundamental limitation.”The research was funded by MIT’s Department of Mechanical Engineering, the Karl van Tassel Career Development Professorship, the Whitaker Health Sciences Fund Fellowship, the T.S. Lin Fellowship, the MIT Undergraduate Research Opportunities Program, and the Boston University Yawkey Funded Internship Program.  More

  • in

    To design better water filters, MIT engineers look to manta rays

    Filter feeders are everywhere in the animal world, from tiny crustaceans and certain types of coral and krill, to various molluscs, barnacles, and even massive basking sharks and baleen whales. Now, MIT engineers have found that one filter feeder has evolved to sift food in ways that could improve the design of industrial water filters.In a paper appearing this week in the Proceedings of the National Academy of Sciences, the team characterizes the filter-feeding mechanism of the mobula ray — a family of aquatic rays that includes two manta species and seven devil rays. Mobula rays feed by swimming open-mouthed through plankton-rich regions of the ocean and filtering plankton particles into their gullet as water streams into their mouths and out through their gills.The floor of the mobula ray’s mouth is lined on either side with parallel, comb-like structures, called plates, that siphon water into the ray’s gills. The MIT team has shown that the dimensions of these plates may allow for incoming plankton to bounce all the way across the plates and further into the ray’s cavity, rather than out through the gills. What’s more, the ray’s gills absorb oxygen from the outflowing water, helping the ray to simultaneously breathe while feeding.“We show that the mobula ray has evolved the geometry of these plates to be the perfect size to balance feeding and breathing,” says study author Anette “Peko” Hosoi, the Pappalardo Professor of Mechanical Engineering at MIT.The engineers fabricated a simple water filter modeled after the mobula ray’s plankton-filtering features. They studied how water flowed through the filter when it was fitted with 3D-printed plate-like structures. The team took the results of these experiments and drew up a blueprint, which they say designers can use to optimize industrial cross-flow filters, which are broadly similar in configuration to that of the mobula ray.“We want to expand the design space of traditional cross-flow filtration with new knowledge from the manta ray,” says lead author and MIT postdoc Xinyu Mao PhD ’24. “People can choose a parameter regime of the mobula ray so they could potentially improve overall filter performance.”Hosoi and Mao co-authored the new study with Irmgard Bischofberger, associate professor of mechanical engineering at MIT.A better trade-offThe new study grew out of the group’s focus on filtration during the height of the Covid pandemic, when the researchers were designing face masks to filter out the virus. Since then, Mao has shifted focus to study filtration in animals and how certain filter-feeding mechanisms might improve filters used in industry, such as in water treatment plants.Mao observed that any industrial filter must strike a balance between permeability (how easily fluid can flow through a filter), and selectivity (how successful a filter is at keeping out particles of a target size). For instance, a membrane that is studded with large holes might be highly permeable, meaning a lot of water can be pumped through using very little energy. However, the membrane’s large holes would let many particles through, making it very low in selectivity. Likewise, a membrane with much smaller pores would be more selective yet also require more energy to pump the water through the smaller openings.“We asked ourselves, how do we do better with this tradeoff between permeability and selectivity?” Hosoi says.As Mao looked into filter-feeding animals, he found that the mobula ray has struck an ideal balance between permeability and selectivity: The ray is highly permeable, in that it can let water into its mouth and out through its gills quickly enough to capture oxygen to breathe. At the same time, it is highly selective, filtering and feeding on plankton rather than letting the particles stream out through the gills.The researchers realized that the ray’s filtering features are broadly similar to that of industrial cross-flow filters. These filters are designed such that fluid flows across a permeable membrane that lets through most of the fluid, while any polluting particles continue flowing across the membrane and eventually out into a reservoir of waste.The team wondered whether the mobula ray might inspire design improvements to industrial cross-flow filters. For that, they took a deeper dive into the dynamics of mobula ray filtration.A vortex keyAs part of their new study, the team fabricated a simple filter inspired by the mobula ray. The filter’s design is what engineers refer to as a “leaky channel” — effectively, a pipe with holes along its sides. In this case, the team’s “channel” consists of two flat, transparent acrylic plates that are glued together at the edges, with a slight opening between the plates through which fluid can be pumped. At one end of the channel, the researchers inserted 3D-printed structures resembling the grooved plates that run along the floor of the mobula ray’s mouth.The team then pumped water through the channel at various rates, along with colored dye to visualize the flow. They took images across the channel and observed an interesting transition: At slow pumping rates, the flow was “very peaceful,” and fluid easily slipped through the grooves in the printed plates and out into a reservoir. When the researchers increased the pumping rate, the faster-flowing fluid did not slip through, but appeared to swirl at the mouth of each groove, creating a vortex, similar to a small knot of hair between the tips of a comb’s teeth.“This vortex is not blocking water, but it is blocking particles,” Hosoi explains. “Whereas in a slower flow, particles go through the filter with the water, at higher flow rates, particles try to get through the filter but are blocked by this vortex and are shot down the channel instead. The vortex is helpful because it prevents particles from flowing out.”The team surmised that vortices are the key to mobula rays’ filter-feeding ability. The ray is able to swim at just the right speed that water, streaming into its mouth, can form vortices between the grooved plates. These vortices effectively block any plankton particles — even those that are smaller than the space between plates. The particles then bounce across the plates and head further into the ray’s cavity, while the rest of the water can still flow between the plates and out through the gills.The researchers used the results of their experiments, along with dimensions of the filtering features of mobula rays, to develop a blueprint for cross-flow filtration.“We have provided practical guidance on how to actually filter as the mobula ray does,” Mao offers.“You want to design a filter such that you’re in the regime where you generate vortices,” Hosoi says. “Our guidelines tell you: If you want your plant to pump at a certain rate, then your filter has to have a particular pore diameter and spacing to generate vortices that will filter out particles of this size. The mobula ray is giving us a really nice rule of thumb for rational design.”This work was supported, in part, by the U.S. National Institutes of Health, and the Harvey P. Greenspan Fellowship Fund.  More

  • in

    Linzixuan (Rhoda) Zhang wins 2024 Collegiate Inventors Competition

    Linzixuan (Rhoda) Zhang, a doctoral candidate in the MIT Department of Chemical Engineering, recently won the 2024 Collegiate Inventors Competition, medaling in both the Graduate and People’s Choice categories for developing materials to stabilize nutrients in food with the goal of improving global health.  The annual competition, organized by the National Inventors Hall of Fame and United States Patent and Trademark Office (USPTO), celebrates college and university student inventors. The finalists present their inventions to a panel of final-round judges composed of National Inventors Hall of Fame inductees and USPTO officials. No stranger to having her work in the limelight, Zhang is a three-time winner of the Koch Institute Image Awards in 2022, 2023, and 2024, as well as a 2022 fellow at the MIT Abdul Latif Jameel Water and Food Systems Lab.  “Rhoda is an exceptionally dedicated and creative student. Her well-deserved award recognizes the potential of her research on nutrient stabilization, which could have a significant impact on society,” says Ana Jaklenec, one of Zhang’s advisors and a principal investigator at MIT’s Koch Institute for Integrative Cancer Research. Zhang is also advised by David H. Koch (1962) Institute Professor Robert Langer. Frameworks for global healthIn a world where nearly 2 billion people suffer from micronutrient deficiencies, particularly iron, the urgency for effective solutions has never been greater. Iron deficiency is especially harmful for vulnerable populations such as children and pregnant women, since it can lead to weakened immune systems and developmental delays. The World Health Organization has highlighted food fortification as a cost-effective strategy, yet many current methods fall short. Iron and other nutrients can break down during processing or cooking, and synthetic additives often come with high costs and environmental drawbacks. Zhang, along with her teammate, Xin Yang, a postdoc associate at Koch Institute, set out to innovate new technologies for nutrient fortification that are effective, accessible, and sustainable, leading to the invention nutritional metal-organic frameworks (NuMOFs) and the subsequent launch of MOFe Coffee, the world’s first iron-fortified coffee. NuMOFs not only protect essential nutrients such as iron while in food for long periods of time, but also make them more easily absorbed and used once consumed.The inspiration for the coffee came from the success of iodized salt, which significantly reduced iodine deficiency worldwide. Because coffee and tea are associated with low iron absorption, iron fortification would directly address the challenge.However, replicating the success of iodized salt for iron fortification has been extremely challenging due to the micronutrient’s high reactivity and the instability of iron(II) salts. As researchers with backgrounds in material science, chemistry, and food technology, Zhang and Yang leveraged their expertise to develop a solution that could overcome these technical barriers. The fortified coffee serves as a practical example of how NuMOFs can help people increase their iron intake by engaging in a habit that’s already part of their daily routine, with significant potential benefits for women, who are disproportionately affected by iron deficiency. The team plans to expand the technology to incorporate additional nutrients to address a wider array of nutritional deficiencies and improve health equity globally.Fast-track to addressing global health improvementsLooking ahead, Zhang and Yang in the Jaklenec Group are focused on both product commercialization and ongoing research, refining MOFe Coffee to enhance nutrient stability and ensuring the product remains palatable while maximizing iron absorption.Winning the CIC competition means that Zhang, Yang, and the team can fast-track their patent application with the USPTO. The team hopes that their fast-tracked patent will allow them to attract more potential investors and partners, which is crucial for scaling their efforts. A quicker patent process also means that the team can bring the technology to market faster, helping improve global nutrition and health for those who need it most. “Our goal is to make a real difference in addressing micronutrient deficiencies around the world,” says Zhang.   More

  • in

    “Mens et manus” in Guatemala

    In a new, well-equipped lab at the University del Valle de Guatemala (UVG) in June 2024, members of two Mayan farmers’ cooperatives watched closely as Rodrigo Aragón, professor of mechanical engineering at UVG, demonstrated the operation of an industrial ultrasound machine. Then he invited each of them to test the device.“For us, it is a dream to be able to interact with technology,” said Francisca Elizabeth Saloj Saloj, a member of the Ija´tz women’s collective, a group from Guatemala’s highlands.After a seven-hour bumpy bus ride, the farmers had arrived in Guatemala City with sacks full of rosemary, chamomile, and thyme. Their objective: to explore processes for extracting essential oils from their plants and to identify new products to manufacture with these oils. Currently, farmers sell their herbs in local markets for medicinal or culinary purposes. With new technology, says Aragón, they can add value to their harvest, using herb oils as the basis for perfumes, syrups, and tinctures that would reach broader markets. These goods could provide much-needed income to the farmers’ households.A strategy for transformationThis collaboration is just one part of a five-year, $15-million project funded by the U.S. Agency for International Development (USAID) and managed by MIT’s Department of Mechanical Engineering in collaboration with UVG and the Guatemalan Export Association (AGEXPORT). Launched in 2021 and called ASPIRE — Achieving Sustainable Partnerships for Innovation, Research, and Entrepreneurship — the project aims to collaboratively strengthen UVG, and eventually other universities in Central America, as problem-solving powerhouses that research, design, and build solutions with and for the people most in need.“The vision of ASPIRE is that within a decade, UVG researchers are collaborating with community members on research that generates results that are relevant to addressing local development challenges — results that are picked up and used by policymakers and actors in the private sector,” says MIT Research Scientist Elizabeth Hoffecker, a co-principal investigator of ASPIRE at MIT, and leader of the Institute’s Local Innovation Group.UVG, one of Guatemala’s top universities, has embraced ASPIRE as part of its long-term strategic plan, and is now pursuing wide-ranging changes based on a playbook developed at MIT — including at MIT D-Lab, which deploys participatory design, co-creation, low-cost technologies, and capacity building to meet the complex challenges of poverty — and piloted at UVG. The ASPIRE team is working to extend the reach of its research innovation and entrepreneurship activities to its two regional campuses and to other regional universities. The overall program is informed by MIT’s approach to development of research-driven innovation ecosystems.Although lacking the resources (and PhD programs) of a typical U.S. university, UVG has big ambitions for itself, and for Guatemala.“We want to thrive and lead the country in research and teaching, and to accomplish this, we are creating an innovation and entrepreneurship ecosystem, based on best practices drawn from D-Lab and other MIT groups,” says Mónica Stein, vice-rector for research and outreach at UVG, who holds a doctorate from Stanford University in plant biology. “ASPIRE can really change the way that development work and local research is done so that it has more impact,” says Stein. “And in theory, if you have more impact, then you improve environmental outcomes, health outcomes, educational outcomes, and economic outcomes.”Local innovation and entrepreneurshipShifting gears at a university and launching novel development initiatives are complex challenges, but with training and workshops conducted by D-Lab-trained collaborators and MIT-based ASPIRE staff, UVG faculty, staff, and students are embracing the change. Programs underway should sound familiar to anyone who has set foot recently on the campus of a U.S. research university: hackathons, makerspaces, pitchapaloozas, entrepreneurship competitions, and spinouts. But at UVG, all of these serve a larger purpose: addressing sustainable development goals.ASPIRE principal investigator Daniel Frey, professor of mechanical engineering at MIT, believes some of these programs are already paying off, particularly a UVG venture mentoring service (VMS), modeled after and facilitated by MIT’s own VMS program. “We’d like to see students building companies and improving their livelihoods and those of people from indigenous and marginalized communities,” says Frey.The ASPIRE project intends to enable the lowest-income communities to share more of Guatemala’s wealth, derived mainly from agricultural goods. In collaborating with AGEXPORT, which enables networking with companies across the country, the team zeroed in on creating or enhancing the value chain for several key crops.“Snow peas offer a great target for both research and innovation,” says Adilia Blandón, ASPIRE research project manager and professor of food engineering at UVG. Many farming communities grow snow peas, which they send along to companies for export to the U.S. Unless these peas are perfect in shape and color, Blandón explains, they don’t make it to market. Nearly a third of Guatemala’s crop is left at processing plants, turned into animal feed, or wasted.An ASPIRE snow pea team located farmers from two cooperatives who wanted to solve this problem. At a series of co-creation sessions, these growers and mechanical engineers at UVG developed a prototype for a low-tech cart for collecting snow peas, made from easily acquired local materials, which can navigate the steep and narrow paths on the hills where the plants grow. This method avoids crushing snow peas in a conventional harvest bag. In addition, the snow pea project has engaged women at a technical school to design a harvest apron for women snow pea farmers. “This could be a business opportunity for them,” Blandón says.Blandón vividly recalls her first ASPIRE workshop, focused on participatory design. “It opened my eyes as a researcher in so many ways,” she says. “I learned that instead of taking information from people, I can learn from them and create things with them that they are really excited about.” It completely changed how she approaches research, she says.Working with Mayan communities that produce snow peas, where malnourishment and illness are rampant, Blandón and ASPIRE researchers found that families don’t eat the protein-packed vegetable because they don’t find it palatable — even though so much of it is left over from harvest. Participatory design sessions with a group of mothers yielded an intriguing possibility: grinding snow peas into flour, which would then be incorporated into traditional bean- and corn-based dishes. The recipes born of this collaboration could land on WhatsApp or TikTok, mobile apps familiar to these families.Building value chainsAdditional research projects are teasing out novel ways of adding value to the products grown or made by Guatemalan hands.These include an educational toolkit developed with government farm extension workers to teach avocado producers how to improve their practices. The long-term goal is to grow and export larger and unblemished fruit for the lucrative U.S. market, currently dominated by Mexico. The kit, featuring simple graphics for growers who can’t read or don’t have the time, offers lessons on soil care, fertilizing, and protecting the fruit post-harvest.ASPIRE UVG Research Director Ana Lucia Solano is especially proud of “an immersive, animated, Monopoly-like game that shows farmers the impact of activities like buying fertilizer on their finances,” she says. “If small producers improve their practices, they will have better opportunities to sell their products at a better price, which may allow them to hire more people, teach others more easily, and offer better jobs and working conditions — and maybe this will help prevent farmworkers from having to leave the country.”Solano has just begun a similar program to educate cocoa producers. “The cocoa of Guatemala is wonderful, but the growers, who have great native knowledge, also need to learn new methods so they can transform their chocolate into the kind of high-quality product expected in European markets, with the help of AGEXPORT,” she says.At the UVG Altiplano campus, Mayan instructor Jeremías Morales, who runs the maker space, trained with Amy Smith, an MIT senior lecturer and founding director of the D-Lab, to facilitate creative capacity-building programs. He is working with nearby villages on a solution for the backbreaking labor of planting broccoli seedlings.“Here in Guatemala, small farm holders don’t have technology to do this task,” says Solano. Through design and prototyping workshops, the village and UVG professors have developed an inexpensive device that accomplishes this painful work. “After their next iteration of this technology, we can support the participants in starting a business,” says Solano.Opportunities to invent solutions to commonplace but vexing problems keep popping up. A small village of 100 families has to share two mills to grind corn for their tortillas. It’s a major household expense. With ASPIRE facilitators, a group of women designed a prototype corn mill for home use. “They were skeptical at first, especially when their initial prototypes didn’t work,” reports Solano, “but when they finally succeeded, there was so much excitement about the results, an energy and happiness that you could feel in the room.”Adopting an MIT mindsetThis feeling of empowerment, a pillar of sustainable development, has great meaning for UVG Professor Victor Hugo Ayerdi, an ASPIRE project manager and director of UVG’s Department of Mechanical Engineering.“In college and after I graduated, I thought since everything came from developed countries, and I was in a developing country, I couldn’t invent products.” With that mindset, he says, he went to work in manufacturing and sales for an international tire manufacturing company.But when he arrived at UVG in 2009, Ayerdi heard from mechanical engineering students who craved practical experience designing and building things. Determined to create maker spaces for the three UVG campuses, he took a field trip to MIT, whose motto is “mens et manus” or “mind and hand.”“The trip changed my life,” he says. “The MIT mindset is to believe in yourself, try things, and fail, but assume there has to be a way to do it.” As a result, he says, he realized UVG faculty and students could also use scientific and engineering knowledge to invent products, become entrepreneurs, spark economic growth; they had the capacity. He and other UVG colleagues were primed for change when the ASPIRE opportunity emerged.As some ASPIRE research projects wind down their initial phases, others are just gearing up, including an effort to fashion a water purification system from the shells of farmed shrimp. “We are only just starting to get results from our research,” says Stein. “But we are totally betting on the ASPIRE model because it works at MIT and other places.”The ASPIRE researchers acknowledge they are looking at long timelines to make significant inroads against environmental, health, educational, and economic challenges.“My greatest hope is that ASPIRE will have planted the seed of this innovation and entrepreneurship ecosystem model, and that in a decade, UVG will have optimized the different programs, whether in training, entrepreneurship, or research, enough to actively transfer them to other Central American universities,” says Stein.“We would like to be the hub of this network and we want to stay connected, because, in theory, we can work together on problems that we have in common in our region. That would be really cool.” More