South China University of Technology

Self-powered wearable garments that double as digital sensors have several advantages over battery-powered devices, primarily because they don’t require batteries. Batteries typically are rigid structures and uncomfortable to wear. Batteries also need recharging. One technological solution for an integrated power source is the triboelectric nanogenerator (TENG). The triboelectric effect produces energy by harnessing electrons when two different materials come in contact with each other. We’ve written about TENGs several times in the past five years, mentioning work by physicists and engineers at Clemson University, Purdue University, and others. Most recently, we covered a prototype battery-free wearable that measures vital signs in real-time developed by researchers at the University of California, Irvine (UCI). According to a team of research engineers from North Carolina State University (NCSU), South China University of Technology, Ocean University of China, and Hong Kong Polytechnic University, producing woven textiles with integrated TENGs is costly, overly complex, and time-consuming. Woven fabric with self-powered sensors also have poor electromechanical properties with limited power capabilities, the research team asserts. Led by the team at NCSU, the group developed a solution to the limitations of self-powered woven textiles. The team published a study in Nano Energy that describes their technology. Rather than try to overcome the challenges of creating power-generating woven fabric, the NCSU-led researchers created a power-generating yarn that is sufficiently durable for embroidery stitching. The yarn consists of five common copper wires, each with a polyurethane insulating coating. The team stitched the yarn onto a two-layer fabric. One layer was cotton denim. The second layer was polytetrafluoroethylene (PTFE). The team stitched the PTFE with the coated wire-based thread. The embroidered patch produced open-circuit voltage and short circuit micro amperage (µA) when the wearer moved. The team embroidered patches that acted as motion sensors on the wearer’s palm, arm, elbow, and knee as well as a numeric keypad. The varied number shapes generated different voltages when pressed. To count steps, the group also stitched an embroidered patch on the insole of a shoe. The engineers tested the embroidered fabric patches by rubbing them 10,000 times and by hand washing and rinsing followed by drying in an oven. There was no significant change following the rubbing abrasion test and either no change or a slight voltage increase after the three-part cleaning cycle. Rong Yin, assistant professor of textile engineering, chemistry and science at North Carolina State University, and the lead author of the study said, “This is a low-cost method for making wearable electronics using commercially available products. The electrical properties of our prototypes were comparable to other designs that relied on the same power generation mechanism.” Next steps include integrating the separate sensors into systems for wearables. Creating self-powering wearables with this method has the advantages of low cost and simple scalability.

Researchers have developed a new way to fortify foods with vitamin A, which they hope could help to improve the health of millions of people around the world. In a new study, they showed that encapsulating vitamin A in a protective polymer prevents the nutrient from being broken down during cooking or storage. Vitamin A deficiency is the world's leading cause of blindness, and in severe cases, it can be fatal. About one-third of the global population of preschool-aged children suffer from this vitamin deficiency, which is most prevalent in sub-Saharan Africa and South Asia. MIT researchers have now developed a new way to fortify foods with vitamin A, which they hope could help to improve the health of millions of people around the world. In a new study, they showed that encapsulating vitamin A in a protective polymer prevents the nutrient from being broken down during cooking or storage. "Vitamin A is a very important micronutrient, but it's an unstable molecule," says Ana Jaklenec, a research scientist at MIT's Koch Institute for Integrative Cancer Research. "We wanted to see if our encapsulated vitamin A could fortify a food vehicle like bouillon cubes or flour, throughout storage and cooking, and whether the vitamin A could remain biologically active and be absorbed." In a small clinical trial, the researchers showed that when people ate bread fortified with encapsulated vitamin A, the bioavailability of the nutrient was similar to when they consumed vitamin A on its own. The technology has been licensed to two companies that hope to develop it for use in food products. "This is a study that our team is really excited about because it shows that everything we did in test tubes and animals works safely and effectively in humans," says Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute. "We hope this opens the door for someday helping millions, if not billions, of people in the developing world." Jaklenec and Langer are the senior authors of the new study, which appears this week in the Proceedings of the National Academy of Sciences. The paper's lead author is former MIT postdoc Wen Tang, who is now an associate professor at South China University of Technology. Nutrient stability Vitamin A is critical not only for vision but also the functioning of the immune system and organs such as the heart and lungs. Efforts to add vitamin A to bread or other foods such as bouillon cubes, which are commonly consumed in West African countries, have been largely unsuccessful because the vitamin breaks down during storage or cooking. In a 2019 study, the MIT team showed that they could use a polymer called BMC to encapsulate nutrients, including iron, vitamin A, and several others. They showed that this protective coating improved the shelf life of the nutrients, and that people who consumed bread fortified with encapsulated iron were able to absorb the iron. BMC is classified by the FDA as "generally regarded as safe," and is already used in coatings for drugs and dietary supplements. In the new study, the researchers focused on using this polymer to encapsulate vitamin A, a nutrient that is very sensitive to temperature and ultraviolet light. Using an industrial process known as a spinning disc process, the researchers mixed vitamin A with the polymer to form particles 100 to 200 microns in diameter. They also coated the particles with starch, which prevents them from sticking to each other. The researchers found that vitamin A encapsulated in the polymer particles were more resistant to degradation by intense light, high temperatures, or boiling water. Under those conditions, much more vitamin A remained active than when the vitamin A was free or when it was delivered in a form called VitA 250, which is currently the most stable form of vitamin A used for food fortification. The researchers also showed that the encapsulated particles could be easily incorporated into flour or bouillon cubes. To test how well they would survive long-term storage, the researchers exposed the cubes to harsh conditions, as recommended by the World Health Organization: 40 degrees Celsius (104 degrees Fahrenheit) and 75 percent humidity. Under those conditions, the encapsulated vitamin A was much more stable than other forms of vitamin A. "The enhanced stability of vitamin A with our technology can ensure that the vitamin A-fortified food does provide the recommended daily uptake of vitamin A, even after long-term storage in a hot humidified environment, and cooking processes such as boiling or baking," Tang says. "People who are suffering from vitamin A deficiency and want to get vitamin A through fortified food will benefit, without changing their daily routines, and without wondering how much vitamin A is still in the food." Vitamin absorption When the researchers cooked their encapsulated particles and then fed them to animals, they found that 30 percent of the vitamin A was absorbed, the same as free uncooked vitamin A, compared to about 3 percent of free vitamin A that had been cooked. Working with Biofortis, a company that does dietary clinical testing, the researchers then evaluated how well vitamin A was absorbed in people who ate foods fortified with the particles. For this study, the researchers incorporated the particles into bread, then measured vitamin A levels in the blood over a 24-hour period after the bread was consumed. They found that when vitamin A was encapsulated in the BMC polymer, it was absorbed from the food at levels comparable to free vitamin A, indicating that it is readily released in bioactive form. Two companies have licensed the technology and are focusing on developing products fortified with vitamin A and other nutrients. A benefit corporation called Particles for Humanity, funded by the Bill and Melinda Gates Foundation, is working with partners in Africa to incorporate this technology into existing fortification efforts. Another company called VitaKey, founded by Jaklenec, Langer, and others, is working on using this approach to add nutrients to a variety of foods and beverages. The research was funded by the Bill and Melinda Gates Foundation. Other authors of the paper include Jia Zhuang, Aaron Anselmo, Xian Xu, Aranda Duan, Ruojie Zhang, James Sugarman, Yingying Zeng, Evan Rosenberg, Tyler Graf, Kevin McHugh, Stephany Tzeng, Adam Behrens, Lisa Freed, Lihong Jing, Surangi Jayawardena, Shelley Weinstock, Xiao Le, Christopher Sears, James Oxley, John Daristotle, and Joe Collins.

A light-activated catalyst efficiently converts ammonia into clean-burning hydrogen using only inexpensive raw materials. Rice University researchers have engineered a key light-activated nanomaterial for the hydrogen economy. Using only inexpensive raw materials, a team from Rice's Laboratory for Nanophotonics, Syzygy Plasmonics Inc. and Princeton University's Andlinger Center for Energy and the Environment created a scalable catalyst that needs only the power of light to convert ammonia into clean-burning hydrogen fuel. The research is published online today in the journal Science. The research follows government and industry investment to create infrastructure and markets for carbon-free liquid ammonia fuel that will not contribute to greenhouse warming. Liquid ammonia is easy to transport and packs a lot of energy, with one nitrogen and three hydrogen atoms per molecule. The new catalyst breaks those molecules into hydrogen gas, a clean-burning fuel, and nitrogen gas, the largest component of Earth's atmosphere. And unlike traditional catalysts, it doesn't require heat. Instead, it harvests energy from light, either sunlight or energy-stingy LEDs. The pace of chemical reactions typically increases with temperature, and chemical producers have capitalized on this for more than a century by applying heat on an industrial scale. The burning of fossil fuels to raise the temperature of large reaction vessels by hundreds or thousands of degrees results in an enormous carbon footprint. Chemical producers also spend billions of dollars each year on thermocatalysts -- materials that don't react but further speed reactions under intense heating. "Transition metals like iron are typically poor thermocatalysts," said study co-author Naomi Halas of Rice. "This work shows they can be efficient plasmonic photocatalysts. It also demonstrates that photocatalysis can be efficiently performed with inexpensive LED photon sources." "This discovery paves the way for sustainable, low-cost hydrogen that could be produced locally rather than in massive centralized plants," said Peter Nordlander, also a Rice co-author. The best thermocatalysts are made from platinum and related precious metals like palladium, rhodium and ruthenium. Halas and Nordlander spent years developing light-activated, or plasmonic, metal nanoparticles. The best of these are also typically made with precious metals like silver and gold. Following their 2011 discovery of plasmonic particles that give off short-lived, high-energy electrons called "hot carriers," they discovered in 2016 that hot-carrier generators could be married with catalytic particles to produce hybrid "antenna-reactors," where one part harvested energy from light and the other part used the energy to drive chemical reactions with surgical precision. Halas, Nordlander, their students and collaborators have worked for years to find non-precious metal alternatives for both the energy-harvesting and reaction-speeding halves of antenna reactors. The new study is a culmination of that work. In it, Halas, Nordlander, Rice alumnus Hossein Robatjazi, Princeton engineer and physical chemist Emily Carter, and others show that antenna-reactor particles made of copper and iron are highly efficient at converting ammonia. The copper, energy-harvesting piece of the particles captures energy from visible light. "In the absence of light, the copper-iron catalyst exhibited about 300 times lower reactivity than copper-ruthenium catalysts, which is not surprising given that ruthenium is a better thermocatalyst for this reaction," said Robatjazi, a Ph.D. alumnus from Halas' research group who is now chief scientist at Houston-based Syzygy Plasmonics. "Under illumination, the copper-iron showed efficiencies and reactivities that were similar to and comparable with those of copper-ruthenium. Syzygy has licensed Rice's antenna-reactor technology, and the study included scaled-up tests of the catalyst in the company's commercially available, LED-powered reactors. In laboratory tests at Rice, the copper-iron catalysts had been illuminated with lasers. The Syzygy tests showed the catalysts retained their efficiency under LED illumination and at a scale 500 times larger than lab setup. "This is the first report in the scientific literature to show that photocatalysis with LEDs can produce gram-scale quantities of hydrogen gas from ammonia," Halas said. "This opens the door to entirely replace precious metals in plasmonic photocatalysis." "Given their potential for significantly reducing chemical sector carbon emissions, plasmonic antenna-reactor photocatalysts are worthy of further study," Carter added. "These results are a great motivator. They suggest it is likely that other combinations of abundant metals could be used as cost-effective catalysts for a wide range of chemical reactions." Halas is Rice's Stanley C. Moore Professor of Electrical and Computer Engineering and a professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering. Nordlander is Rice's Wiess Chair and Professor of Physics and Astronomy, and professor of electrical and computer engineering, and materials science and nanoengineering. Carter is Princeton's Gerhard R. Andlinger Professor in Energy and Environment at the Andlinger Center for Energy and the Environment, senior strategic adviser for sustainability science at the Princeton Plasma Physics Laboratory, and professor of mechanical and aerospace engineering and of applied and computational mathematics. Robatjazi is also an adjunct professor of chemistry at Rice. Halas and Nordlander are Syzygy co-founders and hold an equity stake in the company. The research was supported by the Welch Foundation (C-1220, C-1222), the Air Force Office of Scientific Research (FA9550-15-1-0022), Syzygy Plasmonics, the Department of Defense and Princeton University. Additional co-authors include Yigao Yuan, Jingyi Zhou, Aaron Bales, Lin Yuan, Minghe Lou and Minhan Lou of Rice, Linan Zhou of both Rice and South China University of Technology, Suman Khatiwada of Syzygy Plasmonics, and Junwei Lucas Bao of both Princeton and Boston College.