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Like many of his colleagues in the Department of Biological Engineering, graduate student Tzu-Chieh “Zijay” Tang employs microbes and synthetic biology — redesigning the genetic systems of organisms — in his research. However, his research goals are something of an outlier in his department: water quality applications.
“I feel like there’s a huge imbalance of talent, at least at MIT,” says Tang, a fifth-year doctoral student. “A lot of people go into the biomedical field, and very few take on environmental issues.” To him, problems like climate change or food and water security are the most pressing challenges, and present great opportunities for students in biological engineering to make a difference. While interested in the environment and inspired by the natural world since a young age, he came to appreciate these issues even more, he says, as a result of his experience in 2017 as one of three inaugural fellows through the Fellowship for Water Solutions program at the MIT Abdul Latif Jameel Water and Food Systems Lab (J-WAFS). He points to J-WAFS as a key contributor to raising the profile of environmental research on campus and shifting the imbalance: “J-WAFS really has a vision of a sustainable future, and has been the best supporter of our research — and of me personally, as a researcher.”
When Tang first came to MIT after studying materials science as a master’s student in Abu Dhabi, he joined the Mediated Matter group in the Media Lab. He was excited by the prospect of bioengineering novel materials under the principal investigator, Associate Professor Neri Oxman, “an amazing designer with great visions about how to make materials inspired by nature.” But after a few months, he realized that innovation in biological research, which occurs on a time frame of months to years, can’t keep pace with design deadlines, which tend to be on the order of weeks. Oxman’s group generally worked with fully developed bioengineered systems. Tang, however, preferred to innovate on the fundamental biology itself, and moved to the synthetic biology group of Tim Lu, associate professor of biological engineering and electrical engineering and computer science. Not one to limit his playing field, Tang still chats with Media Lab researchers to glean inspiration.
And Tang’s collaborative spirit extends far afield. A MISTI Seed Grant and a summer at Imperial College London grew into a cross-Atlantic effort to develop living membranes with microbes, in a process inspired by the fermented beverage kombucha. Sweet tea is turned into acidic, fizzy kombucha by a symbiotic culture of bacteria and yeast (SCOBY), which exists in a gelatinous biofilm composed largely of cellulose produced by the bacteria themselves.
The system is self-assembling and requires only a cheap sugar-based solution to maintain, properties that greatly appealed to Tang and his collaborators. Working from the kombucha principle, they developed Syn-SCOBY: a sturdy, cellulose-based biofilm created by and encapsulating a co-culture of engineered microbes. One version of the Syn-SCOBY contained yeast that could detect and degrade the environmental pollutant β-estradiol, but the team emphasized that the modularity of the system meant that it could be customized to target a wide variety of applications.
“People in the lab came to me asking if I could incorporate peptides [amino acid chains] that can bind coronavirus particles into the Syn-SCOBY material,” Tang recalls. “I think this could probably be done quite quickly. That’s why I think developing platform technologies is so useful: you can adapt to different emergencies.” While Tang is well-versed in developing biological materials to address water contamination, it’s in pathogen detection where biosensors have an even greater edge over other more established measurement technology, he says. And while mass spectrometers can detect chemical pollutants reliably, if not necessarily cheaply or in the field, optimizing them to measure biological particles such as viruses has thus far proved difficult.
Tang has already achieved recognition for his research accomplishments — he won a Lemelson-MIT Prize in the “Eat It!” category for his Syn-SCOBY filters. However, what he really wants is to see academic research translated to real applications. One big challenge is scalability, which Tang aims to avoid with his kombucha-inspired biomaterial. Syn-SCOBY is self-replicating, robust, and easy to make. Tang also hopes that the existence of thousands of kombucha homebrewers will make it easier to connect with the public and get them excited about this research.
Four years ago, Tang started developing biosensors in the form of bacteria-containing hydrogel beads. The bacteria are engineered to light up in the presence of water contaminants (he tested this with, among other samples, Charles River water). Formulating the hydrogel was a key aspect of the project: Tang needed the material to not only protect and feed the bacteria, but also to prevent the bacteria from leaking out. Tang continued iterating on his ideas during his J-WAFS fellowship, and has finished developing a bead formulation that not only meets his design requirements, but can be easily adapted to host different microbes.
With real-world applications of his inventions ever on his mind, Tang sought advice on use-case scenarios from industry experts, connections that were made possible through the fellowship’s funder, the international water technology company Xylem. For example, Tang gleaned from the company’s scientists which contaminants were actually of interest to industry, which helped him pick cadmium as a test of the beads’ potential real-world use. Furthermore, he learned that while the beads cannot report measurements as precisely as the gold standard of mass spectrometry, they are much cheaper and much more portable; at the same time, the beads are more precise than probes, which are the current go-to for preliminary testing.
Presently, Tang does not have plans to take his bacteria beads to market, but is nonetheless brainstorming ways to improve them: He sees a potential to increase the system’s sensitivity by incorporating new microbe engineering methods developed in the lab of MIT biological engineering Professor Christopher Voigt. As for Syn-SCOBY, Tang says he might explore the technology’s startup potential through the Blueprint entrepreneurship program offered by The Engine, the startup incubator founded by MIT.
Tang is also contemplating expanding beyond the field of biosensors after graduating in the fall. He feels a strong impetus toward climate change research, especially in advancing carbon removal technology. It’s another area where he sees a yawning gap between academia and application, as well as a long way to go in terms of scalability. In this regard, Tang says the ability of biological systems to self-propagate gives them an advantage over mechanical methods of carbon capture. But he cautions that this same self-propagation makes strict biocontainment of any engineered organisms a vital aspect of any system that is deployed — an aspect that Tang took pains to guarantee in his Syn-SCOBY and microbial hydrogel systems, and an aspect that he will continue to push for in his future work. More

At a young age, Orisa Coombs pledged to use her engineering knowledge to reduce inequality. The summer after her first year of high school, she found herself grappling with the harsh realities of systemic racism after the death of Michael Brown. Brown’s death altered Coombs’ world view and reshaped how she approached her own role in society.“At 15, the intense pain and sense of injustice I felt introduced me to the collective trauma of the Black experience,” says Coombs. “I knew I needed to dedicate my engineering career to issues of oppression and inequality.”
This driving force to make a difference in the world led her to pursue a degree in mechanical engineering at MIT.
“I didn’t want to limit myself to working on a single discipline. There is a design aspect to everything, so I will be capable of working on almost any problem from a mechanical engineering perspective,” she adds.
Once at MIT, Coombs explored research opportunities that improved the lives of others. Her work on medical devices in the MIT Media Lab and with a startup helping rural dairy farmers in India both had a tangible impact, but didn’t quite satisfy her goal of reducing inequality and making a difference on a global scale.Her experience in 11.005 (Introduction to International Development) helped Coombs narrow her research focus to issues affecting the developing world. In particular, she started exploring how climate change disproportionately impacts people of color in developing countries.
“I was seeking research projects that had a connection to climate change and would allow me to develop numerical computation skills,” she says.
This pursuit led her to an undergraduate research opportunity (UROP) in the lab of John Lienhard, the Abdul Latif Jameel Professor of Water and Mechanical Engineering. Lienhard’s group develops energy-efficient methods of producing clean water.
Water scarcity has become a global crisis, particularly in developing countries that are disproportionately impacted by climate change. For her UROP, Coombs joined Lienhard’s efforts to address water scarcity through desalination, the process of turning seawater or brackish water into potable water. 
“It is a fundamental injustice that access to water is not universal,” says Coombs. “Water research sits at the intersection of technology and class-based struggles, while also capitalizing on my fascination with thermofluids engineering.”
Addressing global water scarcity
Coombs’ UROP project focused on a new method of desalination known as osmotically assisted reverse osmosis — or OARO. The OARO process requires less energy and is lower-cost than typical reverse osmosis, making it a promising option for reducing water scarcity in developing nations.
Researchers, however, still don’t understand how membrane diffusion works in OARO, leading to inaccurate performance models. Coombs utilized her background in computation to develop an improved model.
As a Course 2-A (Engineering) major, Coombs’ concentration within mechanical engineering is numerical computation. Her OARO research afforded her the opportunity to apply her numerical computation skills to a real-world project. The resulting computational model of OARO membrane diffusion correlated with experimental data better than existing models.
Coombs and Lienhard hope this model will lead to improved desalination systems in the future, which in turn could reduce water scarcity in developing nations.
“The idea is that eventually we can make desalination a more effective primary water source, especially once fresh water resources are depleted. It’s really promising in terms of how we can change the water landscape and have real impact,” says Coombs.
Coombs presented her model at the 2020 Mechanical Engineering Research Exhibition, where she won the First Place Presenter prize.
“Orisa’s proactiveness and innate interest in research, coupled with her unfailing work ethic, quickly made her an indispensable member of our team,” says Lienhard, “and as I have learned more about Orisa, I have found that she also has a deep commitment to social equity.”
While water scarcity continues to be a driving force in her academic career, Coombs has also been exploring this commitment to equity closer to home at MIT.
Combating food insecurity
During her first year at MIT, Coombs realized how food accessibility impacted individuals in her own friend group. A program called Class Awareness Support and Equality (CASE) at MIT sent grocery care packages to individuals experiencing food insecurity at MIT. When she started noticing some of her friends receiving packages from CASE, she realized just how pervasive the problem was.
Coombs joined CASE as head of food accessibility to help address food insecurity experienced by members of the MIT community. Since her sophomore year, she has been working with administrators across MIT on developing initiatives and programs to help food-insecure students.
Her first project as a member of CASE was to launch small food pantries in dorms that don’t have dining halls. She then shifted her focus to MIT’s on-campus grocery store as a member of the TechMart Advisory Group. She also works with administration on the Food Security Committee to identify further strategies to eradicate hunger.
While her desalination research helps her address inequality on a global scale, her work through CASE has helped her develop solutions in her own community.
“Working with CASE has been part of my journey to realizing that I really am passionate about making those positive changes around me, not just on a global scale,” says Coombs.
Leading the Black Students’ Union through crisis
Last spring, Coombs took on another leadership position to make positive changes across the MIT community as co-chair of the Black Students’ Union (BSU). Shortly after starting as co-chair, Coombs found herself at the helm of the BSU’s response to two crises in the Black community: a pandemic that disproportionately impacted communities of color and protests in the wake of George Floyd’s murder.
Almost overnight, members of the MIT community turned to Coombs for feedback and leadership on behalf of the BSU.
“When I got the role of BSU co-chair, I was not expecting this year to turn out this way,” she says. Coombs seized the opportunity to lead by joining student leaders in writing the Save Black Lives Petition and working closely with senior administration to shape MIT’s response to systemic and institutional racism.
Since last summer, Coombs has helped ensure that MIT’s BSU has an active role in composing the Institute’s 10-year plan to combat racism internally and explore alternatives to current police response practices on campus. She also works on the Institute Steering Committee for Diversity, Equity, and Inclusion as one of three undergraduate representatives. 
“Discussing our values is important, but I want to make sure that we take action. I’m always trying to stay focused on our goals and do right by my community,” says Coombs.
As Coombs looks to the future after graduating this spring, she hopes to continue working on global problems like water scarcity at graduate school. She also sees a chance to have impact on future generations of mechanical engineering students.
“As a Black woman in STEM, I don’t have many role models who look like me. I am excited to provide the mentorship and representation I did not have to the next generation,” she adds. More

Hundreds of students, researchers, and industry experts from around the world gathered virtually in November for a cross-disciplinary exploration of water resilience. More

SMART researchers use Raman spectroscopy for early detection of SAS, which can help farmers better monitor plant health and improve crop yields. More

According to the 2019 NOAA Report on the U.S. Ocean and Great Lakes Economy, Massachusetts is the largest single contributor to the Northeast Blue Economy, accounting for over one-third of the region’s ocean employment and gross domestic product. Challenges caused by Covid-19 have had damaging effects on the seafood industry and far-reaching impacts on the coastal communities that Sea Grant serves. In April, the National Sea Grant Office mobilized funding to support program responses to these challenges.
With closed restaurants and collapsed traditional markets, MIT Sea Grant applied Covid-19 Rapid Response funds to help bridge the divide and develop alternative markets and revenue streams for sustainable aquaculture and fisheries in Massachusetts, including a new project with the Cape Cod Commercial Fishermen’s Alliance (CCCFA): Saving a Community Fishery, Feeding a Population.
Seth Rolbein, director of the Cape Cod Fisheries Trust with the CCCFA, works directly with the small-boat independent fleet in the region. The program has worked with the Cape Cod fishing community for nearly 30 years, engaging with NOAA Fisheries Greater Atlantic Regional Fisheries Office, fishing regulators, scientists, stock assessors, and policymakers to ensure that the independent fishers don’t get shut out of the fishery.
But with Covid-19 came immediate concerns for the fleet of about 50 small boats. “The bottom fell out of the market,” Rolbein says. “Meanwhile, the whole overseas supply chain broke down.” Some found creative solutions like selling directly off boats with special permission from the state. The fishers he works with are used to uncertainty — whether it’s the weather, the price, the crew, or the equipment. “These are very resilient, smart, entrepreneurial, small business people,” says Rolbein. Still, the global pandemic added a challenging layer of uncertainty.
Seeking solutions, MIT Sea Grant first connected with the New England Fisheries Management Council, the Greater Boston Food Bank, and the Massachusetts Department of Agricultural Resources. “A unique strength in the MIT Sea Grant Program is our Advisory Group that has established and maintains a network of stakeholders — industry, state and federal agencies, academia, and the public — that drive and provide ideas for our [work],” says Michael Triantafyllou, MIT Sea Grant director and the Henry L. and Grace Doherty Professor of Ocean Science and Engineering.
Rob Vincent, assistant director for advisory services, found that there was interest in bringing local seafood into the Massachusetts Emergency Food Assistance Program, the MassGrown Initiative, and the private nonprofit food bank network. “We identified potential local fishing groups and the concept of a fisheries-to-food banks program to support the fishing community and families that depend on the state food bank system,” he says, “a need that expanded during the crisis as more people found themselves out of work.”
Next, Vincent reached out to the CCCFA. Five years ago, they created a program called Fish for Families, distributing over 50,000 pounds of fish through local food pantries. During Covid-19, they had the idea to scale up with a concept for haddock chowder that could be frozen and packaged in individual portions, branded “Small Boats, Big Taste”.
“MIT Sea Grant has played a really instrumental role in helping to get us going and really allow us to build the first key phase of this whole project,” Rolbein says. MIT Sea Grant was able to connect the CCCFA with the greater food bank network and Department of Agriculture in Massachusetts, and provide initial funding to create a new market for small haddock, a challenging segment of the fishery. These haddock, although abundant, don’t fillet well, and fishers don’t get a great price for them. “The beauty of the chowder is you don’t put a single big fillet in,” says Rolbein. Historically, chowder and haddock were staples of the New England fishing industry. “It’s kind of a return to an old tradition.”
The aim is to create a good market for smaller haddock as a sustainable long-term model to support the fishing community and contribute to the food pantry system. John Pappalardo, CEO of the CCCFA, explains, “Fishermen will be paid a reliable fair market value for their landed haddock, allowing them to continue to work despite the pandemic’s many challenges.”
With the pandemic, Triantafyllou adds, “We felt an obligation to give back and help our stakeholders — especially our industry and fellow citizens in a time of crisis. We are very proud of this program.” In addition to compensating fishers for their harvest, the project now supports a whole chain of fish-related businesses and jobs. The haddock are filleted at the Boston processing facility Great Eastern Seafood, and the chowder is prepared in Lowell by local soup company, the Plenus Group. Rolbein explains, “Both uses [of the funding] have direct impact and make it possible for Massachusetts-based fishermen to remain viable and working, despite serious market repercussions caused by the pandemic.”​
To launch a program like this, Rolbein says, “Particularly if the goal is to support food banks, you need places like MIT Sea Grant that see the benefits of it and can support it.” Additional funding for the project comes from Catch Together, a nonprofit that works with small-boat fishing fleets around the country connecting locally-caught seafood with communities.
The haddock chowder program is already taking shape across the state, with aims to expand on a national level. The first donated batches, totaling around 36,000 pounds of haddock chowder, translate to 96,000 individual meals. “We just finished our second run of chowder, and we’ll probably be doing these once every three or four weeks,” Rolbein says. Oysters or quahogs could become the basis for the next round of chowder or stew. “We can slowly begin to diversify based on what fishermen need and what they have.”
As the CCCFA and innovative local fishing fleets navigate new challenges, programs like the MIT Sea Grant COVID Rapid Response Funding provide important opportunities to help keep them on the water and in business. The haddock chowder is more than a meal; it’s a recipe for resilience, livelihoods, sustainable ocean resources, and strengthened connections in our local communities and economies. More

For smallholder farmers living in hot and arid regions, getting fresh crops to market and selling them at the best price is a balancing act. If crops aren’t sold early enough, they wilt or ripen too quickly in the heat, and farmers have to sell them at reduced prices. Selling produce in the morning is a strategy many farmers use to beat the heat and ensure freshness, but that results in oversupply and competition at markets and further reduces the value of the produce sold. If farmers could chill their harvests — maintaining cool temperatures to keep them fresh for longer — then they could bring high-quality, fresh produce to afternoon markets and sell at better prices. Access to cold storage could also allow growers to harvest more produce before heading to markets, making these trips more efficient and profitable while also expanding consumers’ access to fresh produce.
Unfortunately, many smallholder farming communities lack access to the energy resources needed to support food preservation technologies like refrigeration. To address this challenge, an MIT research team funded by a 2019 seed grant from the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) is combining expertise in mechanical engineering, architecture, and energy systems to design affordable off-grid cold storage units for perishable crops. Three MIT principal investigators are leading this effort: Leon Glicksman, professor of building technology and mechanical engineering in the Department of Architecture; Daniel Frey, a professor in the Department of Mechanical Engineering and the faculty director for research at MIT D-Lab; and Eric Verploegen, a research engineer at MIT D-Lab. They are also collaborating with researchers at the University of Nairobi to study the impact of several different chamber designs on performance and usability in Kenya. Together, they are looking to develop a cost-effective large-scale cooperative storage facility that uses the evaporative cooling properties of water to keep harvests fresher, longer.
Evaporative cooling
Evaporative cooling involves the energy dynamics of the phase change of water from its liquid state into its gas state. Simply put, when dry air moves across a saturated surface such as a container full of water, the water molecules absorb a large amount of heat as they change from liquid to gas, cooling the surrounding air. Evaporative cooling isn’t a new concept. People have been leveraging this property of water to cool buildings and keep harvests fresh for thousands of years. Today, in many arid regions, people use a double clay pot system to harness the evaporative cooling process to prolong the freshness of fruit and vegetables. Known as a pot-in-pot cooler or Zeer pot, the space between a larger and smaller ceramic pot is filled with sand and kept wet. As water evaporates through the vessel walls, it lowers the temperature of the inner chamber. 
However, while clay pot coolers can be effective for individual household use, they are limited by their storage capacity. Some larger-scale produce storage strategies that use evaporative cooling exist and are in use in Kenya and other countries and arid regions. In fact, Verploegen has focused his research at MIT D-Lab on evaporative cooling technologies since 2016, resulting in the production of several designs currently at the pilot stage.
Yet size still remains a challenge. Few designs exist today that are large enough to effectively store several metric tons of produce and that satisfy important criteria like ease of construction, quality of performance, and affordability, which would meet the storage needs for larger harvests or groups of farmers. Designs exist for solar-powered mechanical refrigeration; however, the costs associated with the energy, implementation, and maintenance of these units is prohibitive to many smallholder farmers around the world. Teaming up with Frey and Gliskman for this J-WAFS-funded effort, the group is aiming to address this lack of access. “For us, the questions became, ‘How can we scale evaporative cooling techniques and improve upon the existing ways that people have been using it for centuries?’” Glicksman reflects. With this in mind, the team set out to find a solution.
Sustainability as a design throughline
Initially the team’s focus was on improving the performance of existing cooling chamber technologies. “We worked with local folks [in Kenya] and built some of the more traditional designs that use charcoal,” says Verploegen. “However, what we found was that these efforts were very labor-intensive, time-consuming, and overall not very replicable.” Building on the ongoing user research performed by teams at the University of Nairobi and MIT D-Lab, the researchers have been exploring different kinds of materials for the structure, and settled on shipping containers as the basis for the chamber. 
As it turns out, the height and width of a shipping container meets the dimension specifications of users’ requirements. Plus, using shipping containers provides the opportunity to up-cycle existing, used materials. “I’m always checking out where used shipping containers are available and checking prices in various countries for our cost model,” Verploegen admits. So, in their current design, they retrofitted a shipping container with a double-layered insulating wall, a solar-powered fan to force air through a central matrix of wet pads, and interior storage crates arranged to maximize convection and cooling rates and ease of use. 
This design is informed by several analytical models that the research team continues to develop. The models evaluate the effect that different evaporative cooling materials, arrangements of produce storage crates, and exterior insulating materials have on the efficiency and functionality of the cooling chamber. These models help maximize cooling capabilities while minimizing water and energy usage, and also inform decisions on material choices.
One such decision was the transition away from wetted charcoal as an evaporative cooling medium. Charcoal is commonly used as a cooling membrane material, but the release of CO2 during the burn-treatment process and subsequent negative environmental effects made it less attractive to the team. Currently, they are experimenting with plant-based aspen fiber and corrugated cellulose pads, which are both a cost-effective and environmentally sustainable solution. Lastly, the team has installed a solar-powered electronic control system that allows farmers to automate the chamber’s fan and water pumps, increasing efficiency and minimizing maintenance requirements. 
Collaborating overseas
Critical to the research project’s development is collaboration with researchers at the University of Nairobi (UON) in Kenya. Professor Jane Ambuko, a leading horticulturist at UON in the Department of Plant Science and Crop Protection, is well-versed in post-harvest technologies. In addition to her expert knowledge on crop physiology and the effects of cooling on produce, Ambuko is well-connected within the local Kenyan farming community and has provided the team with critical introductions to local farmers willing to test out the team’s chamber prototypes. Another collaborator, Duncan Mbuge, an agricultural engineer in the UON Department of Environmental and Biosystems Engineering, has been able to provide insight into the design, construction, and materials selection for the cooling chambers.
The project has also involved exchange between MIT D-Lab and UON students, and this collaboration has opened up additional avenues for both institutions to work together. “The exchange of ideas [with MIT] has been mutually beneficial,” says Mbuge, “the net result has been an overall improvement in the technology.” The two professors, along with their research students, have continued monitoring and managing the pilot structure built in Kenya. “Together, with expertise from the MIT team, we complete each other­,” adds Ambuko.
“The researchers at UON have a whole history and institutional knowledge of challenges that previously tried designs have come up against in real-world contexts,” Verploegen says, adding this has been essential to moving the MIT designs from concept to practice. Farmers have also played a major role in shaping the design and implementation of this technology. Following the D-Lab model, the MIT and UON research teams worked together to run a number of interviews and focus groups in farming communities in order to learn directly from users about their needs. The farmers in these communities have important insights into how to design a practical and effective cooling chamber that is suitable for use by farming cooperatives. Given that it will have more than one user, farmers have asked for a crate-stacking arrangement that will allow for easy inventory management. Farmers have pointed out additional benefits of the evaporative cooling chambers. “We have been told that these containers can also provide special protection from rodents,” Frey explains, “that turns out to be a very important for the farmers that we’re working with.”
Potential impacts
Overall, the team’s models indicate that a standard 40-foot-long shipping container outfitted as an evaporative cooler will be able to store between 6,500-8,000 kilograms of produce. The cost of constructing the chamber will likely be $7,000-$8,000, which, compared to mechanically refrigerated options of a similar size, offers over a 50 percent reduction in cost, making this new design very lucrative for farming cooperatives. One of the ways the team is keeping the production costs down is by using local materials and a centralized manufacturing strategy. “We are of the mindset that building a technology of this size and complexity centrally and then distributing it locally is the best way to make it accessible and affordable for these communities,” Verploegen says. 
There are many benefits to making technologies accessible to and replicable by members of specific communities. Collaborative development is a cornerstone of D-Lab’s work, the academics and research program that Verploegen and Frey are a part of. “At D-Lab, we’re interested in planting the idea that community involvement is critical in order to adapt technological solutions to people’s needs and to maximize their use of the resulting solution,” says Frey. While an emphasis on co-creation is expected to result in community buy-in for their cooling solution, centralized manufacturing and construction of the containers is an additional strategy aimed at ensuring the accessibility and affordability of the technology for the communities they aim to serve. 
While the current design has been developed for farmers near Nairobi in Kenya, these evaporative cooling devices could be deployed in a host of other regions in Kenya, as well as parts of West Africa and regions of western India such as Rajasthan and Gujarat. Verploegen, who is also leading a related J-WAFS-funded effort on evaporative cooling through the J-WAFS Grant for Water and Food Projects in India, is developing designs for crop storage for farms in western India. He says that “the scale of need is what determines what kind of evaporative cooling technology a community might need.” His work in India is focused on helping to disseminate technologies that are smaller and constructed at the location where they will be used, using brick and sand. He is also “helping to make them more efficient and improving the design to best fit local needs.”
Ultimately, the research team’s goal is to make their evaporative cooling chamber something that local farming communities will consistently use and benefit from. To do this, they have to “come up with not only the MIT solution, but a solution that the people on the ground find is the best for them,” says Glicksman. They hope that this technology will not only help producers economically, but that it will also enable widespread food storage and preservation capabilities, allowing better access for populations to fresh produce.
To read more about this work, visit the project site via J-WAFS. More

Researchers at MIT and elsewhere have significantly boosted the output from a system that can extract drinkable water directly from the air even in dry regions, using heat from the sun or another source.
The system, which builds on a design initially developed three years ago at MIT by members of the same team, brings the process closer to something that could become a practical water source for remote regions with limited access to water and electricity. The findings are described today in the journal Joule, in a paper by Professor Evelyn Wang, who is head of MIT’s Department of Mechanical Engineering; graduate student Alina LaPotin; and six others at MIT and in Korea and Utah.
The earlier device demonstrated by Wang and her co-workers provided a proof of concept for the system, which harnesses a temperature difference within the device to allow an adsorbent material — which collects liquid on its surface — to draw in moisture from the air at night and release it the next day. When the material is heated by sunlight, the difference in temperature between the heated top and the shaded underside makes the water release back out of the adsorbent material. The water then gets condensed on a collection plate.
But that device required the use of specialized materials called metal organic frameworks, or MOFs, which are expensive and limited in supply, and the system’s water output was not sufficient for a practical system. Now, by incorporating a second stage of desorption and condensation, and by using a readily available adsorbent material, the device’s output has been significantly increased, and its scalability as a potentially widespread product is greatly improved, the researchers say.

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Wang says the team felt that “It’s great to have a small prototype, but how can we get it into a more scalable form?” The new advances in design and materials have now led to progress in that direction.
Instead of the MOFs, the new design uses an adsorbent material called a zeolite, which in this case is composed of a microporous iron aluminophosphate. The material is widely available, stable, and has the right adsorbent properties to provide an efficient water production system based just on typical day-night temperature fluctuations and heating with sunlight.
The two-stage design developed by LaPotin makes clever use of the heat that is generated whenever water changes phase. The sun’s heat is collected by a solar absorber plate at the top of the box-like system and warms the zeolite, releasing the moisture the material has captured overnight. That vapor condenses on a collector plate — a process that releases heat as well. The collector plate is a copper sheet directly above and in contact with the second zeolite layer, where the heat of condensation is used to release the vapor from that subsequent layer. Droplets of water collected from each of the two layers can be funneled together into a collecting tank.
In the process, the overall productivity of the system, in terms of its potential liters per day per square meter of solar collecting area (LMD), is approximately doubled compared to the earlier version, though exact rates depend on local temperature variations, solar flux, and humidity levels. In the initial prototype of the new system, tested on a rooftop at MIT before the pandemic restrictions, the device produced water at a rate “orders of magnitude” greater that the earlier version, Wang says.
While similar two-stage systems have been used for other applications such as desalination, Wang says, “I think no one has really pursued this avenue” of using such a system for atmospheric water harvesting (AWH), as such technologies are known.
Existing AWH approaches include fog harvesting and dew harvesting, but both have significant limitations. Fog harvesting only works with 100 percent relative humidity, and is currently used only in a few coastal deserts, while dew harvesting requires energy-intensive refrigeration to provide cold surfaces for moisture to condense on — and still requires humidity of at least 50 percent, depending on the ambient temperature.
By contrast, the new system can work at humidity levels as low as 20 percent and requires no energy input other than sunlight or any other available source of low-grade heat.
LaPotin says that the key is this two-stage architecture; now that its effectiveness has been shown, people can search for even better adsorbent materials that could further drive up the production rates. The present production rate of about 0.8 liters of water per square meter per day may be adequate for some applications, but if this rate can be improved with some further fine-tuning and materials choices, this could become practical on a large scale, she says. Already, materials are in development that have an adsorption about five times greater than this particular zeolite and could lead to a corresponding increase in water output, according to Wang.
The team continues work on refining the materials and design of the device and adapting it to specific applications, such as a portable version for military field operations. The two-stage system could also be adapted to other kinds of water harvesting approaches that use multiple thermal cycles per day, fed by a different heat source rather than sunlight, and thus could produce higher daily outputs.
“This is an interesting and technologically significant work indeed,” says Guihua Yu, a professor of materials science and mechanical engineering at the University of Texas at Austin, who was not associated with this work. “It represents a powerful engineering approach for designing a dual-stage AWH device to achieve higher water production yield, marking a step closer toward practical solar-driven water production,” he says.
Yu adds that “Technically, it is beautiful that one could reuse the heat released simply by this dual-stage design, to better confine the solar energy in the water harvesting system to improve energy efficiency and daily water productivity. Future research lies in improving this prototype system with low cost components and simple configuration with minimized heat loss.”
The research team includes Yang Zhong, Lenan Zhang, Lin Zhao, and Arny Leroy at MIT; Hyunho Kim at the Korea Institute of Science and Technology; and Sameer Rao at the University of Utah. The work was supported by the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT. More

MIT engineers have designed a Velcro-like food sensor, made from an array of silk microneedles, that pierces through plastic packaging to sample food for signs of spoilage and bacterial contamination.
The sensor’s microneedles are molded from a solution of edible proteins found in silk cocoons, and are designed to draw fluid into the back of the sensor, which is printed with two types of specialized ink. One of these “bioinks” changes color when in contact with fluid of a certain pH range, indicating that the food has spoiled; the other turns color when it senses contaminating bacteria such as pathogenic E. coli.
The researchers attached the sensor to a fillet of raw fish that they had injected with a solution contaminated with E. coli. After less than a day, they found that the part of the sensor that was printed with bacteria-sensing bioink turned from blue to red — a clear sign that the fish was contaminated. After a few more hours, the pH-sensitive bioink also changed color, signaling that the fish had also spoiled.
The results, published today in the journal Advanced Functional Materials, are a first step toward developing a new colorimetric sensor that can detect signs of food spoilage and contamination.
Such smart food sensors might help head off outbreaks such as the recent salmonella contamination in onions and peaches. They could also prevent consumers from throwing out food that may be past a printed expiration date, but is in fact still consumable.
“There is a lot of food that’s wasted due to lack of proper labeling, and we’re throwing food away without even knowing if it’s spoiled or not,” says Benedetto Marelli, the Paul M. Cook Career Development Assistant Professor in MIT’s Department of Civil and Environmental Engineering. “People also waste a lot of food after outbreaks, because they’re not sure if the food is actually contaminated or not. A technology like this would give confidence to the end user to not waste food.”
Marelli’s co-authors on the paper are Doyoon Kim, Yunteng Cao, Dhanushkodi Mariappan, Michael S. Bono Jr., and A. John Hart.
Silk and printing
The new food sensor is the product of a collaboration between Marelli, whose lab harnesses the properties of silk to develop new technologies, and Hart, whose group develops new manufacturing processes.
Hart recently developed a high-resolution floxography technique, realizing microscopic patterns that can enable low-cost printed electronics and sensors. Meanwhile, Marelli had developed a silk-based microneedle stamp that penetrates and delivers nutrients to plants. In conversation, the researchers wondered whether their technologies could be paired to produce a printed food sensor that monitors food safety.
“Assessing the health of food by just measuring its surface is often not good enough. At some point, Benedetto mentioned his group’s microneedle work with plants, and we realized that we could combine our expertise to make a more effective sensor,” Hart recalls.
The team looked to create a sensor that could pierce through the surface of many types of food. The design they came up with consisted of an array of microneedles made from silk.
“Silk is completely edible, nontoxic, and can be used as a food ingredient, and it’s mechanically robust enough to penetrate through a large spectrum of tissue types, like meat, peaches, and lettuce,” Marelli says.
A deeper detection
To make the new sensor, Kim first made a solution of silk fibroin, a protein extracted from moth cocoons, and poured the solution into a silicone microneedle mold. After drying, he peeled away the resulting array of microneedles, each measuring about 1.6 millimeters long and 600 microns wide — about one-third the diameter of a spaghetti strand.
The team then developed solutions for two kinds of bioink — color-changing printable polymers that can be mixed with other sensing ingredients. In this case, the researchers mixed into one bioink an antibody that is sensitive to a molecule in E. coli. When the antibody comes in contact with that molecule, it changes shape and physically pushes on the surrounding polymer, which in turn changes the way the bioink absorbs light. In this way, the bioink can change color when it senses contaminating bacteria.
The researchers made a bioink containing antibodies sensitive to E. coli, and a second bioink sensitive to pH levels that are associated with spoilage. They printed the bacteria-sensing bioink on the surface of the microneedle array, in the pattern of the letter “E,” next to which they printed the pH-sensitive bioink, as a “C.” Both letters initially appeared blue in color.
Kim then embedded pores within each microneedle to increase the array’s ability to draw up fluid via capillary action. To test the new sensor, he bought several fillets of raw fish from a local grocery store and injected each fillet with a fluid containing either E. coli, Salmonella, or the fluid without any contaminants. He stuck a sensor into each fillet. Then, he waited.
After about 16 hours, the team observed that the “E” turned from blue to red, only in the fillet contaminated with E. coli, indicating that the sensor accurately detected the bacterial antigens. After several more hours, both the “C” and “E” in all samples turned red, indicating that every fillet had spoiled.
The researchers also found their new sensor indicates contamination and spoilage faster than existing sensors that only detect pathogens on the surface of foods.
“There are many cavities and holes in food where pathogens are embedded, and surface sensors cannot detect these,” Kim says. “So we have to plug in a bit deeper to improve the reliability of the detection. Using this piercing technique, we also don’t have to open a package to inspect food quality.”
The team is looking for ways to speed up the microneedles’ absorption of fluid, as well as the bioinks’ sensing of contaminants. Once the design is optimized, they envision the sensor could be used at various stages along the supply chain, from operators in processing plants, who can use the sensors to monitor products before they are shipped out, to consumers who may choose to apply the sensors on certain foods to make sure they are safe to eat.
This research was supported, in part, by the MIT Abdul Latif Jameel Water and Food Systems Lab (J-WAFS), the U.S. National Science Foundation, and the U.S. Office of Naval Research. More