MIT: Lighting the Way to Better Battery Technology


MIT New Battery 0720 Supratim_Das_9Supratim Das is determined to demystify lithium-ion batteries, by first understanding their flaws.  Photo: Lillie Paquette/School of Engineering

Doctoral candidate Supratim Das wants the world to know how to make longer-lasting batteries that charge mobile phones and electric cars.

Supratim Das’s quest for the perfect battery began in the dark. Growing up in Kolkata, India, Das saw that a ready supply of electric power was a luxury his family didn’t have. “I wanted to do something about it,” Das says. Now a fourth-year PhD candidate in MIT chemical engineering who’s months away from defending his thesis, he’s been investigating what causes the batteries that power the world’s mobile phones and electric cars to deteriorate over time.

Lithium-ion batteries, so-named for the movement of lithium ions that make them work, power most rechargeable devices today. The element lithium has properties that allow lithium-ion batteries to be both portable and powerful; the 2019 Nobel Prize in Chemistry was awarded to scientists who helped develop them in the late 1970s. But despite their widespread use, lithium-ion batteries, essentially a black box during operation, harbor mysteries that prevent scientists from unlocking their full potential. Das is determined to demystify them, by first understanding their flaws.

In principle, rechargeable batteries shouldn’t expire. In practice, however, they can only be recharged a finite number of times before they lose their ability to hold a charge. An ordinary battery eventually stops working when the terminals of the battery — called electrodes — are permanently altered by the ions passing from one terminal of the battery to the other. In a rechargeable battery, the electrodes recover when an external charger sends those ions back where they came from.

Lithium ion batteries work the same way. Typically, one electrode is made of graphite, and the other of lithium compounds with transition metals such as iron, cobalt, or nickel. At the lithium electrode, lithium atoms part ways with their electrons, swim through the battery fluid (electrolyte), and wait at the other electrode. Meanwhile, the electrons take the long way around. They flow out the battery, through a device that needs the power, and into the second electrode, where they rejoin the lithium ions. When a mobile phone is plugged in to be charged, the ions and electrons retrace their steps, and the battery can be used again.

When a battery is charged, however, not all the lithium ions make it back. Every charging cycle leaves ions straggling at the graphite electrode, and the battery loses capacity over time. Das found this perplexing, because it meant that draining a phone’s battery didn’t harm it, but recharging it did. He addressed this conundrum in a couple of open-access academic publications in 2019.

There was also another problem. When a battery is “fast-charged” — a feature that comes with many of the latest electronics — lithium ions start layering (plating) over the carbon electrode, instead of transporting (intercalating) into the material. Prolonged lithium plating can cause uncontrolled growth of fractal-like dendrites. This can cause short-circuiting, even fires.

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In his doctoral research, Das and collaborators have been able to understand the microscopic changes that degrade a battery’s electrodes over its lifetime, and develop multiscale physics-based models to predict them in a robust manner at the macro-scale.

Such multiscale models can aid battery manufacturers to substantially reduce battery health diagnostics costs before it is incorporated into a device, and make batteries safer for consumers. In his latest project, he’s using that knowledge to investigate the best way of charging a lithium-ion battery without damaging it. Das hopes his contributions help scientists achieve further breakthroughs in battery science and make batteries safer, especially when the latest technology is often closely guarded by private companies. “What our group is trying to do is improve the quality of open access academic literature,” Das says. “So that when other people are trying to start their research in batteries, they don’t have to start at the theory from five to 10 years ago.”

Das is well-placed to walk between the worlds of academia and industry.

As an undergraduate in Indian Institute of Technology (IIT) Delhi, Das learned that chemical engineers could use equations and experiments to invent technology like drugs and semi-conductors. “Just the fact that here I was in college, learning something that gave me the power to potentially impact the lives of N number of people in a positive manner, was utterly fascinating to me,” Das says. He also interned at a consumer goods company, where he realized that academia would allow him more freedom to pursue ambitious ideas.

In his sophomore year, Das wrote to a professor at the Hong Kong University of Science and Technology, seeking an opportunity to do research. He flew out that summer, and spent weeks learning about high-power lithium-ion batteries. “It was an eye-opening experience,” Das recalls. He returned to his coursework, but the idea of working on batteries had taken hold. “I never thought that something I can do with my own hands can potentially make impact at the scale that battery technology does,” Das says. He continued working on research projects and made key contributions in the field of multiphase chemical reaction engineering during his undergraduate degree, and eventually wound up applying to the graduate program at MIT.

In his second year of graduate work, Das spent a semester as a technical consultant for Shell in Houston, Texas and Emirates Global Aluminum in Dubai. There, he learned lessons that would prove invaluable in his graduate work. “It taught me problem formulation,” Das says. “Identifying what is relevant for stakeholders; what to work on so as to best use the team’s skill sets; how to distribute your time.”

After Das’s experience in the field, he discovered that as a scientist he could share valuable knowledge about battery research and the future of the technology with energy economists. He also realized that policymakers considered their own criteria when investing in technology for the future.

Das believed that such a perspective would help him inform policy decisions as a scientist, so he decided that after completing his PhD, he would pursue an MBA focusing on energy economics and policy at MIT’s Sloan School of Management. “It will allow me to contribute more to society if I’m able to act as a bridge between someone who understands the hardcore, microscopic physics of a battery, and someone who understands the economic and policy implications of introducing that battery into a vehicle or a grid,” Das says.

Das believes that the program, which begins next fall, will allow him to work with other energy experts who bring their own knowledge and skills to the table. He understands the power of collaboration well: at college, Das was elected president of a dorm of 450-plus residents and worked with students and administration to introduce new facilities and events on campus. After arriving in Cambridge, Massachusetts, Das helped other students manage Ashdown House, represented chemical engineering students on the Graduate Student Advisory Board, and served in the leadership team for the MIT Energy Club, spearheading the organization of MIT EnergyHack 2019.

He also launched a community service initiative within the Department of Chemical Engineering; once a week, students mentor school children and volunteer at nonprofits in Cambridge. He was able to attract funding for his initiative and was awarded by the department for successfully mobilizing 80-plus students in the community within the span of a year. “I’m constantly surprised at what we can achieve when we work with other people,” Das says.

After all, other people have helped Das make it this far. “I owe a lot of success to a number of sacrifices my mom made for me, including giving up her own career,” he says. At MIT, he feels fortunate to have met mentors like his advisor, Martin Bazant, and Practice School directors Robert Fisher and Brian Stutts, and the many colleagues who have offered answers to his questions. “Here, I’ve discovered what it means to synergize with really smart people who are really passionate — and really nice at the same time,” Das says. “Grateful is the one word I’d use.”

Buzzing to rebuild broken bone


Buzzing a broken bone bonefracture

Healing broken bones could get easier with a device that provides both a scaffold for the bone to grow on and electrical stimulation to urge it forward, UConn engineers reported on June 27 in the Journal of Nano Energy.

Although minor bone breaks usually heal on their own, large fractures with shattered or missing chunks of bone are more difficult to repair. Applying a tiny electrical field to the site of the fracture to mimic the body’s natural electrical field helps the cells regenerate. But the  that do this are usually bulky, rely on electrical wires or toxic batteries, require invasive removal surgery, and can’t do much for serious injuries.

Now, a group of biomedical engineers from UConn have developed a  of non-toxic polymer that also generates a controllable electrical field to encourage bone growth. The scaffold helps the body bridge large fractures. Although many scientists are exploring the use of scaffolding to encourage bone growth, pairing it with  is new.

The team demonstrated the device in mice with skull .

The  the scaffold generates is very small, just a few millivolts. And uniquely for this type of device, the voltage is generated via remotely-controlled ultrasound. The ultrasound vibrates the polymer scaffolding, which then creates an electrical field (materials that create electricity from vibration, or vice versa, are called piezoelectric.) To help heal a thigh fracture, for example, the polymer scaffold can be implanted across the broken bone. Later, the person with the broken bone can wave the ultrasound wand over their own thigh themselves. No need for batteries, and no need for invasive removal surgery once the bone is healed.

“The  relates to the natural signal generated by your body at the injury location. We can sustain that voltage, on demand and reversible,” for however long is needed using ultrasound, says UConn biomedical engineer Thanh Nguyen. The piezoelectric polymer Nguyen and his colleagues use to build the scaffold is called poly(L-lactic acid), or PLLA. In addition to being non-toxic and piezoelectric, PLLA gradually dissolves in the body over time, disappearing as the new bone grows.

“The electric field created by the piezoelectric PLLA scaffold seems to attract bone cells to the site of the fracture and promote stem cells to evolve into bone cells. This technology can possibly be combined with other factors to facilitate regeneration of other tissues, like cartilage, muscles or nerves,” says Ritopa Das, a  in Nguyen group and the first author of the published paper.

Currently Nguyen and his colleagues are working to make the polymer more favorable to bone growth, so that it heals a large fracture more quickly. They are also trying to understand why electrical fields encourage bone growth at all. Bone itself is somewhat piezoelectric, generating a surface charge when the bone is stressed by everyday life activities. That surface charge encourages more bone to grow. But scientists don’t know whether it’s because it helps cells stick to the surface of the , or whether it makes the cells themselves more active.

“Once we understand the mechanism, we can devise a better way to improve the material and the whole approach of tissue stimulation,” Nguyen says.


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EU’s Exploding Demand for Anode Materials for Lithium-Ion Batteries Creates Opportunity for Australia’s Talga Resources to Capture Significant Market Share as a Local ‘Non-Asia’ Source Provider


Graphene anode Talga-Talnode-graphic
 

Posted By Graphene Council, Friday, June 26, 2020

Overwhelming European demand sees Australia’s battery anode company Talga Resources plan for expanded output at its new Swedish battery anode factory.

Expressions of interest received for Talga’s lithium-ion battery anode products exceed 300% of planned annual capacity of the Vittangi Anode Project, the company says.

Talnode products are now in 36 active commercial engagements covering the majority of planned European li-ion battery manufacturers and six major global automotive OEMs.

Talga says it’s expanding the scale of the Niska scoping study for the Vittangi Project to review larger anode production options as a result of this significant interest.

Li-ion battery megafactories are set to require more than 2.5 million tonnes per annum (tpa) active anode material by 2029, up from about 450,000 tpa anode production today, with Europe the fastest growing market.

That’s because worldwide li-ion battery demand continues to rapidly increase, with global battery manufacturing capacity set to exceed 2.5 tera-Watt hours (TWh) per annum by 2029 across 142 battery plants.

“Our engagement with European battery companies and automotive OEMs has grown rapidly, with customers attracted by the potential of locally produced anode at competitive costs and with world-leading sustainability,” Talga managing director Mark Thompson says.

Graphene Anode Mark-Thompson-Talga-Resource

”As we progress Talnode-C through commercial qualification stages with customers it is pleasing to note that interest now greatly exceeds our original planned production, and that the need to review expansion options has arisen this early.”

The increased interest means the company is targeting completion of the Niska scoping study in Q3 2020.

While COVID-19 has severely impacted EV sales in the short term, Bloomberg New Energy Finance data shows EV sales hold up better than internal combustion engine (ICE) vehicles due to new (lower cost) models and supportive government policies.

In the quarters prior to the COVID-19 outbreak, EV sales as a percentage of total passenger vehicles rose rapidly in the EU, with Germany and France recording increases of 100% during the period.

Numerous countries across Europe have implemented some form of financial incentives towards customer uptake of EVs, and post COVID-19 these have increased markedly in some countries.

Talga is entering the European market at a time when 100% of anode supply is still sourced from Asia. The company’s marketing team reports that, post COVID-19, localisation is becoming an increasingly significant factor influencing customer’s purchasing decisions.

NC State University has developed a Flexible Carbon Nanotube Film with a unique combination of thermal, electrical and physical properties that make it an an Excellent Candidate for Next-Generation of Smart Fabrics


Carbon NTs that Heat and Cool id55557_1

Researchers reported in a new study that a material made of carbon nanotubes may be key in developing clothing that can heat or cool the wearer on demand. The film is twisted into a filament yarn and wound around a tube to show its flexibility. (Image: Kony Chatterjee)

A film made of carbon nanotubes (CNT) may be a key material in developing clothing that can heat or cool the wearer on demand. A new North Carolina State University study finds that the CNT film has a combination of thermal, electrical and physical properties that make it an appealing candidate for next-generation smart fabrics.

The researchers were also able to optimize the thermal and electrical properties of the material, allowing the material to retain its desirable properties even when exposed to air for many weeks. Moreover, these properties were achieved using processes that were relatively simple and did not need excessively high temperatures.
“Many researchers are trying to develop a material that is non-toxic and inexpensive, but at the same time is efficient at heating and cooling,” said Tushar Ghosh, co-corresponding author of the study (ACS Applied Energy Materials“In-plane Thermoelectric Properties of Flexible and Room Temperature Processable Doped Carbon Nanotube Films”). “Carbon nanotubes, if used appropriately, are safe, and we are using a form that happens to be inexpensive, relatively speaking. So it’s potentially a more affordable thermoelectric material that could be used next to the skin.” Ghosh is the William A. Klopman Distinguished Professor of Textiles in NC State’s Wilson College of Textiles.
“We want to integrate this material into the fabric itself,” said Kony Chatterjee, first author of the study and a Ph.D. student at NC State. “Right now, the research into clothing that can regulate temperature focuses heavily on integrating rigid materials into fabrics, and commercial wearable thermoelectric devices on the market aren’t flexible either.”
To cool the wearer, Chatterjee said, CNTs have properties that would allow heat to be drawn away from the body when an external source of current is applied.
“Think of it like a film, with cooling properties on one side of it and heating on the other,” Ghosh said.
The researchers measured the material’s ability to conduct electricity, as well as its thermal conductivity, or how easily heat passes through the material.
One of the biggest findings was that the material has relatively low thermal conductivity – meaning heat would not travel back to the wearer easily after leaving the body in order to cool it. That also means that if the material were used to warm the wearer, the heat would travel with a current toward the body, and not pass back out to the atmosphere.
The researchers were able to accurately measure the material’s thermal conductivity through a collaboration with the lab of Jun Liu, an assistant professor of mechanical and aerospace engineering at NC State. The researchers used a special experimental design to more accurately measure the material’s thermal conductivity in the direction that the electric current is moving within the material.
“You have to measure each property in the same direction to give you a reasonable estimate of the material’s capabilities,” said Liu, co-corresponding author of the study. “This was not an easy task; it was very challenging, but we developed a method to measure this, especially for thin flexible films.”
The research team also measured the ability of the material to generate electricity using a difference in temperature, or thermal gradient, between two environments. Researchers said that they could take advantage of this for heating, cooling, or to power small electronics.
Liu said that while these thermoelectric properties were important, it was also key that they found a material that was also flexible, stable in air, and relatively simple to make.
“The point of this paper isn’t that we achieved the best thermoelectric performance,” Liu said. “We achieved something that can be used as a flexible, electronic, soft material that’s easy to fabricate. It’s easy to prepare this material, and easy to achieve these properties.”
Ultimately, their vision for the project is to design a smart fabric that can heat and cool the wearer, along with energy harvesting. They believe that a smart garment could help reduce energy consumption.
“Instead of heating or cooling a whole dwelling or space, you would heat or cool the personal space around the body,” Ghosh said. “If we could get the thermostat down a degree or two, that could save a tremendous amount of energy.”
Source: North Carolina State University

NEWT – Opportunities for Nanotechnology to Enhance Electrochemical Treatment of Pollutants in Potable Water and Industrial Wastewater -A perspective 


Abstract

Based upon an international workshop, this perspective evaluates how nano-scale pore structures and unique properties that emerge at nano- and sub-nano- size domains could improve the energy efficiency and selectivity of electroseparation or electrocatalytic processes for treating potable or waste waters.

An Eisenhower matrix prioritizes the urgency or impact of addressing potential barriers or opportunities. There has been little optimization of electrochemical reactors to increase mass transport rates of pollutants to, from, and within electrode surfaces, which become important as nano-porous structures are engineered into electrodes. A “trap-and-zap” strategy is discussed wherein nanostructures (pores, sieves, and crystal facets) are employed to allow localized concentration of target pollutants relative to background solutes (i.e., localized pollutant trapping).

The trapping is followed by localized production of tailored reactive oxygen species to selectively degrade the target pollutant (i.e., localized zapping). Frequently overlooked in much of the electrode-material development literature, nano-scale structures touted to be highly “reactive” towards target pollutants may also be the most susceptible to material degradation (i.e., aging) or fouling by mineral scales that form due to localized pH changes.

A need exists to study localized pH and electric-field related aging or fouling mechanisms and strategies to limit or reverse adverse outcomes from aging or fouling. This perspective provides examples of the trends and identifies promising directions to advance nano-materials and engineering principles to exploit the growing need for near chemical-free, advanced oxidation/reduction or separation processes enabled through electrochemistry.

CONTRIBUTORS – NEWT (Nano Enabled Water Treatment)

Rice, ASU, Yale, UTEP win NSF engineering research cente

MIT: Carbon nanotube transistors make the leap from lab to factory floor


The next major revolution in computer chip technology is now a step closer to reality. Researchers have shown that carbon nanotube transistors can be made rapidly in commercial facilities, with the same equipment used to manufacture traditional silicon-based transistors – the backbone of today’s computing industry. 

Carbon nanotube field-effect transistors (CNFETs) are more energy-efficient than silicon field-effect transistors and could be used to build a new generation of three-dimensional microprocessors. But until now, these devices have been mostly restricted to academic laboratories with only small numbers produced.

However, in a new study this month – published in the journal Nature Electronics – scientists have demonstrated how CNFETs can be fabricated in large quantities on 200-millimetre wafers: the industry standard for computer chip design. The CNFETs were created in a commercial silicon manufacturing facility and a semiconductor foundry in the United States.

Having analysed the deposition technique used to make the CNFETs, a team at the Massachusetts Institute of Technology (MIT) developed a way of speeding up the fabrication process by more than 1,100 times compared to previous methods, while also reducing the cost.

Their technique deposited the carbon nanotubes edge to edge on wafers, with CFNET arrays of 14,400 by 14,400 distributed across multiple wafers.

Max Shulaker, an MIT assistant professor of electrical engineering and computer science, who has been designing CNFETs since his PhD days, says the new study represents “a giant step forward, to make that leap into production-level facilities.”

Bridging the gap between lab and industry is something that researchers “don’t often get a chance to do,” he added. “But it’s an important litmus test for emerging technologies.”

 

 

For decades, improvements in silicon-based transistor manufacturing have brought down prices and increased energy efficiency in computing. Concerns are mounting that this trend may be nearing its end, however, as increasing numbers of transistors packed into integrated circuits do not appear to be increasing energy efficiency at historic rates. CNFETs are an attractive alternative technology because they are “around an order of magnitude more energy efficient” than silicon-based transistors, says Shulaker.

While silicon-based transistors are typically made at temperatures of 450 to 500 degrees Celsius, CNFETs can be manufactured at near-room temperatures.

“This means that you can actually build layers of circuits right on top of previously fabricated layers of circuits, to create a 3D chip,” Shulaker explains. “You can’t do this with silicon-based technology, because it would melt the layers underneath.” 

A 3D computer chip, which might combine logic and memory functions, is projected to “beat the performance of a state-of-the-art 2D chip made from silicon by orders of magnitude,” he says.

One of the most effective ways to build CFNETs in the lab is a method for depositing nanotubes called incubation – illustrated below – where a wafer is submerged in a bath of nanotubes until the nanotubes stick to the wafer’s surface.

The performance of the CNFET depends in large part on the deposition process, explains co-author Mindy Bishop, a PhD student in the Harvard-MIT Health Sciences and Technology program. This affects both the number of carbon nanotubes on the surface of the wafer and their orientation. They are “either stuck onto the wafer in random orientations like cooked spaghetti, or all aligned in the same direction like uncooked spaghetti still in the package.”

Aligning the nanotubes perfectly in a CNFET leads to ideal performance, but alignment is difficult to obtain, says Bishop: “It’s really hard to lay down billions of tiny 1-nanometre diameter nanotubes in a perfect orientation across a large 200-millimetre wafer. To put these length scales into context, it’s like trying to cover the entire state of New Hampshire in perfectly oriented, dry spaghetti.” 

While the incubation method employed by the MIT team is unable to perfectly align every nanotube (perhaps a breakthrough in future years may achieve this?), their experiments showed that it delivers sufficiently high performance for a CNFET to outperform a traditional silicon-based transistor. 

Furthermore, careful observations revealed how to alter the process to make it more viable for large-scale commercial production. For instance, Bishop’s team found that “dry cycling”, a method of intermittently drying out the submerged wafer, could drastically reduce the incubation time – from 48 hours to 150 seconds. Another new method called artificial concentration through evaporation (ACE) deposited small amounts of nanotube solution on a wafer, instead of submerging the wafer in a tank. The slow evaporation of the solution increased the overall density of nanotubes on the wafer. 

The researchers worked with Analog Devices, a commercial silicon manufacturing facility, and SkyWater Technology, a semiconductor foundry, to fabricate CNFETs using the improved methods. They were able to use the same equipment that the two facilities use to make silicon-based wafers, while also ensuring that the nanotube solutions met strict chemical and contaminant requirements of the facilities. 

The next steps, already underway, will be to build different types of integrated circuits out of CNFETs in an industrial setting and explore some of the new functions that a 3D chip could offer, adds Shulaker. 

“The next goal is for this to transition from being academically interesting to something that will be used by folks, and I think this is a very important step in this direction,” he concludes.

Carbon Nanotube Second Skin Protects First Responders and Warfighters against Chem, Bio Agents – Lawrence Livermore National Laboratory


Published 8 May 2020

Recent events such as the COVID-19 pandemic and the use of chemical weapons in the Syria conflict have provided a stark reminder of the plethora of chemical and biological threats that soldiers, medical personnel and first responders face during routine and emergency operations. Researchers have developed a smart, breathable fabric designed to protect the wearer against biological and chemical warfare agents. Material of this type could be used in clinical and medical settings as well.

Recent events such as the COVID-19 pandemic and the use of chemical weapons in the Syria conflict have provided a stark reminder of the plethora of chemical and biological threats that soldiers, medical personnel and first responders face during routine and emergency operations.

Personnel safety relies on protective equipment which, unfortunately, still leaves much to be desired. For example, high breathability (i.e., the transfer of water vapor from the wearer’s body to the outside world) is critical in protective military uniforms to prevent heat-stress and exhaustion when soldiers are engaged in missions in contaminated environments.

The same materials (adsorbents or barrier layers) that provide protection in current garments also detrimentally inhibit breathability.

To tackle these challenges, a multi-institutional team of researchers led by Lawrence Livermore National Laboratory (LLNL) scientist Francesco Fornasiero has developed a smart, breathable fabric designed to protect the wearer against biological and chemical warfare agents. Material of this type could be used in clinical and medical settings as well.

The work was recently published online in Advanced Functional Materials and represents the successful completion of Phase I of the project, which is funded by the Defense Threat Reduction Agency through the Dynamic Multifunctional Materials for a Second Skin “D[MS]“ program.

“We demonstrated a smart material that is both breathable and protective by successfully combining two key elements: a base membrane layer comprising trillions of aligned carbon nanotube pores and a threat-responsive polymer layer grafted onto the membrane surface,” Fornasiero said.

LLNL notes that these carbon nanotubes (graphitic cylinders with diameters more than 5,000 times smaller than a human hair) could easily transport water molecules through their interiors while also blocking all biological threats, which cannot fit through the tiny pores.

This key finding was previously published in Advanced Materials.

The team has shown that the moisture vapor transport rate through carbon nanotubes increases with decreasing tube diameter and, for the smallest pore sizes considered in the study, is so fast that it approaches what one would measure in the bulk gas phase.

This trend is surprising and implies that single‐walled carbon nanotubes (SWCNTs) as moisture conductive pores overcome a limiting breathability/protection trade-off displayed by conventional porous materials, according to Fornasiero. Thus, size-sieving selectivity and water-vapor permeability can be simultaneously enhanced by decreasing SWCNT diameters.

Contrary to biological agents, chemical threats are smaller and can fit through the nanotube pores. To add protection against chemical hazards, a layer of polymer chains is grown on the material surface, which reversibly collapses in contact with the threat, thus temporarily blocking the pores.

“This dynamic layer allows the material to be ‘smart’ in that it provides protection only when and where it is needed,” said Timothy Swager, a collaborator at the Massachusetts Institute of Technology who developed the responsive polymer. These polymers were designed to transition from an extended to a collapsed state in contact with organophosphate threats, such as sarin. “We confirmed that both simulants and live agents trigger the desired volume change,” Swager added.

The team showed that the responsive membranes have enough breathability in their open-pore state to meet the sponsor requirements. In the closed state, the threat permeation through the material is dramatically reduced by two orders of magnitude. The demonstrated breathability and smart protection properties of this material are expected to translate in a significantly improved thermal comfort for the user and enable to greatly extend the wear time of protective gears, whether in a hospital or battlefield.

“The safety of warfighters, medical personnel and first responders during prolonged operations in hazardous environments relies on personal protective equipment that not only protects but also can breathe,” said Kendra McCoy, the DTRA program manager overseeing the project.

“DTRA Second Skin program is designed to address this need by supporting the development of new materials that adapt autonomously to the environment and maximize both comfort and protection for many hours.”

In the next phase of the project, the team will aim to incorporate on-demand protection against additional chemical threats and make the material stretchable for a better body fit, thus more closely mimicking the human skin.

‘Artificial leaf’ concept inspires research into solar-powered fuel production: Rice University


A schematic and electron microscope cross-section show the structure of an integrated, solar-powered catalyst to split water into hydrogen fuel and oxygen. The module developed at Rice University can be immersed into water directly to produce fuel when exposed to sunlight. Credit: Jia Liang/Rice University

Rice University researchers have created an efficient, low-cost device that splits water to produce hydrogen fuel.

The platform developed by the Brown School of Engineering lab of Rice materials scientist Jun Lou integrates catalytic electrodes and  that, when triggered by sunlight, produce electricity. The current flows to the catalysts that turn water into hydrogen and oxygen, with a sunlight-to-hydrogen efficiency as high as 6.7%.

This sort of catalysis isn’t new, but the lab packaged a  layer and the electrodes into a single module that, when dropped into water and placed in sunlight, produces hydrogen with no further input.

The  introduced by Lou, lead author and Rice postdoctoral fellow Jia Liang and their colleagues in the American Chemical Society journal ACS Nano is a self-sustaining producer of  that, they say, should be simple to produce in bulk.

“The concept is broadly similar to an artificial leaf,” Lou said. “What we have is an integrated module that turns sunlight into electricity that drives an electrochemical reaction. It utilizes water and sunlight to get chemical fuels.”

Perovskites are crystals with cubelike lattices that are known to harvest light. The most efficient perovskite  produced so far achieve an efficiency above 25%, but the materials are expensive and tend to be stressed by light, humidity and heat.

“Jia has replaced the more expensive components, like platinum, in perovskite solar cells with alternatives like carbon,” Lou said. “That lowers the entry barrier for commercial adoption. Integrated devices like this are promising because they create a system that is sustainable. This does not require any external power to keep the module running.”

Liang said the key component may not be the perovskite but the polymer that encapsulates it, protecting the module and allowing to be immersed for long periods.

“Others have developed catalytic systems that connect the solar cell outside the water to immersed electrodes with a wire,” he said. “We simplify the system by encapsulating the perovskite layer with a Surlyn (polymer) film.”

The patterned film allows sunlight to reach the solar cell while protecting it and serves as an insulator between the cells and the electrodes, Liang said.

“With a clever system design, you can potentially make a self-sustaining loop,” Lou said. “Even when there’s no sunlight, you can use stored energy in the form of chemical fuel. You can put the hydrogen and oxygen products in separate tanks and incorporate another module like a fuel cell to turn those fuels back into electricity.”

The researchers said they will continue to improve the encapsulation technique as well as the solar themselves to raise the efficiency of the modules.

More information: Jia Liang et al, A Low-Cost and High-Efficiency Integrated Device toward Solar-Driven Water Splitting, ACS Nano (2020). DOI: 10.1021/acsnano.9b09053

Journal information: ACS Nano

Provided by Rice University

Breathable’ Electronics Pave the Way for More Functional Wearable Tech


This sleeve incorporates the new electronic material, allowing it to function as a video game controller.

Engineering researchers have created ultrathin, stretchable electronic material that is gas permeable, allowing the material to “breathe.” The material was designed specifically for use in biomedical or wearable technologies, since the gas permeability allows sweat and volatile organic compounds to evaporate away from the skin, making it more comfortable for users – especially for long-term wear.

“The gas permeability is the big advance over earlier stretchable electronics,” says Yong Zhu, co-corresponding author of a paper on the work and a professor of mechanical and aerospace engineering at North Carolina State University. “But the method we used for creating the material is also important because it’s a simple process that would be easy to scale up.”

Specifically, the researchers used a technique called the breath figure method to create a stretchable polymer film featuring an even distribution of holes. The film is coated by dipping it in a solution that contains silver nanowires. The researchers then heat-press the material to seal the nanowires in place.

“The resulting film shows an excellent combination of electric conductivity, optical transmittance and water-vapor permeability,” Zhu says. “And because the silver nanowires are embedded just below the surface of the polymer, the material also exhibits excellent stability in the presence of sweat and after long-term wear.”

“The end result is extremely thin – only a few micrometers thick,” says Shanshan Yao, co-author of the paper and a former postdoctoral researcher at NC State who is now on faculty at Stony Brook University. “This allows for better contact with the skin, giving the electronics a better signal-to-noise ratio.

“And gas permeability of wearable electronics is important for more than just comfort,” Yao says. “If a wearable device is not gas permeable, it can also cause skin irritation.”

To demonstrate the material’s potential for use in wearable electronics, the researchers developed and tested prototypes for two representative applications.

The first prototype consisted of skin-mountable, dry electrodes for use as electrophysiologic sensors. These have multiple potential applications, such as measuring electrocardiography (ECG) and electromyography (EMG) signals.

“These sensors were able to record signals with excellent quality, on par with commercially available electrodes,” Zhu says.

The second prototype demonstrated textile-integrated touch sensing for human-machine interfaces. The authors used a wearable textile sleeve integrated with the porous electrodes to play computer games such as Tetris. Related video can be seen at https://youtu.be/7AO_cq8A_BE.

“If we want to develop wearable sensors or user interfaces that can be worn for a significant period of time, we need gas-permeable electronic materials,” Zhu says. “So this is a significant step forward.”

The paper, “Gas-Permeable, Ultrathin, Stretchable Epidermal Electronics with Porous Electrodes,” is published in the journal ACS Nano. First author of the paper is Weixin Zhou, a Ph.D. student at Nanjing University of Posts and Telecommunications (NUPT) who worked on the project while a visiting scholar at NC State.

The paper was co-authored by Hongyu Wang, a Ph.D. student at NC State, and by Qingchuan Du of NUPT. Co-corresponding author of the paper is Yanwen Ma, a professor at NUPT.

The work was done with support from the National Science Foundation, under grant number CMMI-1728370.

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Note to Editors: The study abstract follows.

“Gas-Permeable, Ultrathin, Stretchable Epidermal Electronics with Porous Electrodes”

Authors: Weixin Zhou, Qingchuan Du and Yanwen Ma, Nanjing University of Posts and Telecommunications; Shanshan Yao, North Carolina State University and Stony Brook University; and Hongyu Wang and Yong Zhu, North Carolina State University

Published: April 29, ACS Nano

DOI: 10.1021/acsnano.0c00906

Abstract: We present gas-permeable, ultrathin, and stretchable electrodes enabled by self-assembled porous substrates and conductive nanostructures. Efficient and scalable breath figure method is employed to introduce the porous skeleton and then silver nanowires (AgNWs) are dip-coated and heat-pressed to offer electric conductivity.

The resulting film has a transmittance of 61%, sheet resistance of 7.3 Ω/sq, and water vapor permeability of 23 mg cm-2 h-1. With AgNWs embedded below the surface of the polymer, the electrode exhibits excellent stability with the presence of sweat and after long-term wear.

We demonstrate the promising potential of the electrode for wearable electronics in two representative applications – skin-mountable biopotential sensing for healthcare and textile-integrated touch sensing for human-machine interfaces.

The electrode can form conformal contact with human skin, leading to low skin-electrode impedance and high quality biopotential signals. In addition, the textile electrode can be used in a self-capacitance wireless touch sensing system.

University of Maryland Engineers Open Door to Big New Library of Tiny Nanoparticles


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The development of bimetallic nanoparticles (i.e., tiny particles composed of two different metals that exhibit several new and improved properties) represents a novel area of research with a wide range of potential applications.

Now, a research team in the University of Maryland (UMD)’s Department of Materials Science and Engineering (MSE) has developed a new method for mixing metals generally known to be immiscible, or unmixable, at the nanoscale to create a new range of bimetallic materials.

Such a library will be useful for studying the role of these bimetallic particles in various reaction scenarios such as the transformation of carbon dioxide to fuel and chemicals.

The study, led by MSE Professor Liangbing Hu, was published in Science Advances on April 24, 2020. Chunpeng Yang, an MSE Research Associate, served as first author on the study.

“With this method, we can quickly develop different bimetallics using various elements, but with the same structure and morphology,” said Hu. “Then we can use them to screen catalytic materials for a reaction; such materials will not be limited by synthesizing difficulties.”

The complex nature of nanostructured bimetallic particles makes mixing such particles difficult, for a variety of reasons—including the chemical makeup of the metals, particle size, and how metals arrange themselves at the nanoscale—using conventional methods.

This new non-equilibrium synthesismethod exposes copper-based mixes to a thermal shock of approximately 1300 ̊ Celsius for .02 seconds and then rapidly cools them to room temperature. The goal of using such a short interval of thermal heat is to quickly trap, or ‘freeze,’ the high-temperature metal atoms at room temperature while maintaining their mixing state.

In doing so, the research team was able to prepare a collection of homogeneous copper-based alloys. Typically, copper only mixes with a few other metals, such as zinc and palladium—but by using this new method, the team broadened the miscible range to include copper with nickel, iron, and silver, as well.

“Using a scanning electron microscope (SEM) and transmission electron microscope (TEM), we were able to confirm the morphology – how the materials formed – and size of the resulting Cu-Ag [copper-silver] bimetallic nanoparticles,” Yang said.

This method will enable scientists to create more diverse nanoparticle systems, structures, and materials having applications in catalysis, biological applications, optical applications, and magnetic materials.

As a model system for rapid catalyst development, the team investigated copper-based alloys as catalysts for carbon monoxide reduction reactions, in collaboration with Feng Jiao, a professor in the Department of Chemical and Biomolecular Engineering at the University of Delaware.

The electro-catalysis of carbon monoxide reduction (COR) is an attractive platform, allowing scientists to use greenhouse gas and renewable electrical energy to produce fuels and chemicals.

“Copper is, thus far, the most promising monometallic electrocatalyst that drives carbon monoxide reduction to value-added chemicals,” said Jiao. “The ability to rapidly synthesize a wide variety of copper-based bimetallic nanoalloys with a uniform structure enables us to conduct fundamental studies on the structure-property relationship in COR and other catalyst systems.”

This non-equilibrium synthetic strategy can be extended to other bimetallic or metal oxide systems, too. Utilizing artificial intelligence-based machine learning, the method will make rapid catalyst screening and rational design possible.

For additional information:

Yang, C., et al. (24 April 2020). Overcoming Immiscibility Toward Bimetallic Catalyst Library, Science Advances. DOI: 10.1126/sciadv.aaz6844