UC San Diego: Printed, flexible and rechargeable battery can power Wearable Sensors, Solar Cells, Electronics

Stretchable printed batteries

 

Nanoengineers at the University of California San Diego have developed the first printed battery that is flexible, stretchable and rechargeable. The zinc batteries could be used to power everything from wearable sensors to solar cells and other kinds of electronics.

The work appears in the April 19, 2017 issue of Advanced Energy Materials.

The researchers made the printed batteries flexible and stretchable by incorporating a hyper-elastic polymer material made from isoprene, one of the main ingredients in rubber, and polystyrene, a resin-like component. The substance, known as SIS, allows the batteries to stretch to twice their size, in any direction, without suffering damage.

The ink used to print the batteries is made of zinc silver oxide mixed with SIS. While zinc batteries have been in use for a long time, they are typically non-rechargeable. The researchers added bismuth oxide to the batteries to make them rechargeable.

“This is a significant step toward self-powered stretchable electronics,” said Joseph Wang, one of the paper’s senior authors and a nanoengineering professor at the Jacobs School of Engineering at UC San Diego, where he directs the school’s Center for Wearable Sensors. “We expect this technology to pave the way to enhance other forms of energy storage and printable, stretchable electronics, not just for zinc-based batteries but also for Lithium-ion batteries, as well as supercapacitors and photovoltaic cells.”

The prototype battery the researchers developed has about 1/5 the capacity of a rechargeable hearing aid battery. But it is 1/10 as thick, cheaper and uses commercially available materials. It takes two of these batteries to power a 3 Volt LED. The researchers are still working to improve the battery’s performance. Next steps include expanding the use of the technology to different applications, such as solar and fuel cells; and using the battery to power different kinds of electronic devices.

Researchers used standard screen printing techniques to make the batteries–a method that dramatically drives down the costs of the technology. Typical materials for one battery cost only $0.50. A comparable commercially available rechargeable battery costs $5.00 Batteries can be printed directly on fabric or on materials that allow wearables to adhere to the skin. They also can be printed as a strip, to power a device that needs more energy. They are stable and can be worn for a long period of time.

Making the batteries rechargeable

The key ingredient that makes the batteries rechargeable is a molecule called bismuth oxide which, when mixed into the batteries’ zinc electrodes, prolongs the life of devices and allows them to recharge. Adding bismuth oxide to zinc batteries is standard practice in industry to improve performance, but until recently, there hasn’t been a thorough scientific explanation for why.

Last year, UC San Diego nanoengineers led by Professor Y. Shirley Meng published a detailed molecular study addressing this question (download PDF here). When zinc batteries discharge, their electrodes react with the liquid electrolyte inside the battery, producing zinc salts that dissolve into a solution. This eventually short circuits the battery. Adding bismuth oxide keeps the electrode from losing zinc to the electrolyte. This ensures that the batteries continue to work and can be recharged.

The work shows that it is possible to use small amounts of additives, such as bismuth oxide, to change the properties of materials. “Understanding the scientific mechanism to do this will allow us to turn non-rechargeable batteries into rechargeable batteries—not just zinc batteries but also for other electro-chemistries, such as Lithium-oxygen,” said Meng, who directs the Sustainable Power and Energy Center at the UC San Diego Jacobs School of Engineering

From Innovation to Market

Rajan Kumar, a co-first author on this Advanced Energy Materials paper, is a nanoengineering Ph.D. student at the Jacobs School of Engineering. He and nanoengineering professor Wang are leading a team focused on commercializing aspects of this work. The team is one of five to be selected to join a new technology accelerator at UC San Diego. The technology accelerator is run by the UC San Diego Institute for the Global Entrepreneur, which is a collaboration between the Jacobs School of Engineering and Rady School of Management.

Kumar is excited at the prospect of taking advantage of all that the IGE Technology Accelerator has to offer.

“For us, it’s strategically perfect,” said Kumar, referring to the $50,000 funding for prototype improvements, the focus on prototype testing with a strategic partner, and the entrepreneurship mentoring.

Kumar is confident in the team’s innovations, which includes the ability to replace coin batteries with thin, stretchable batteries. Making the right strategic moves now is critical for commercialization success.

“It’s now about making sure our energies are focused in the right direction,” said Kumar.

In addition to the IGE Technology Accelerator, the team was also recently selected to participate in the NSF Innovation-Corps (I-Corps) program at UC San Diego, also administered by the Institute for the Global Entrepreneur. One of the key tenets of the I-Corps program is helping startup teams validate their target markets and business models early in the commercialization process. Through NSF I-Corps, for example, Kumar has already started interviewing potential customers which has helped the team better focus their commercialization strategy.

Through these programs, Kumar is focused on leading the team through a series of milestones in order to best position their innovations to refine “both what to build and who to build it for,” he said.

Paper Citation

“All-Printed, Stretchable Zn-Ag₂O Rechargeable Battery via Hyperelastic Binder for Self-Powering Wearable Electronics” in the journal Advanced Energy Materials.http://onlinelibrary.wiley.com/doi/10.1002/aenm.201602096/full

Authors: Rajan Kumar, Jaewook Shin, Lu Yin, Jung-Min You, Prof. Shirley Meng and Prof. Joseph Wang, Department of Nanoengineering, Jacobs School of Engineering, University of California San Diego.

Joseph Wang is a distinguished professor, holds the SAIC endowed chair, and serves as chair of the Department of NanoEngineering at the UC San Diego Jacobs School of Engineering where he directs the Center for Wearable Sensors.

Shirley Meng is a professor in the Department of NanoEngineering and Director of the Sustainable Power and Energy Center at the UC San Diego Jacobs School of Engineering.

Research funders include: Advanced Research Projects Agency-Energy (DE-AR0000535); Rajan Kumar acknowledges the U.S. National Science Foundation (NSF) Graduate Research Fellowship under Grant No (DGE-1144086).

This work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI), a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the U.S. National Science Foundation (NSF).

Update: MIT; UC San Diego; Harvard Universities: Energy-carrying particles called ‘topological plexcitons’ could make possible the design of ‘next generation’ solar cells and miniaturized optical circuitry

Plexcitons travel for 20,000 nanometers, a length which is on the order of the width of human hair. Credit: Joel Yuen-Zhou

Scientists at UC San Diego, MIT and Harvard University have engineered “topological plexcitons,” energy-carrying particles that could help make possible the design of new kinds of solar cells and miniaturized optical circuitry.

The researchers report their advance in an article published in the current issue of Nature Communications.

Within the Lilliputian world of solid state physics, light and matter interact in strange ways, exchanging energy back and forth between them.

“When light and matter interact, they exchange energy,” explained Joel Yuen-Zhou, an assistant professor of chemistry and biochemistry at UC San Diego and the first author of the paper. “Energy can flow back and forth between light in a metal (so called plasmon) and light in a molecule (so called exciton). When this exchange is much faster than their respective decay rates, their individual identities are lost, and it is more accurate to think about them as hybrid particles; excitons and plasmons marry to form plexcitons.” 

Materials scientists have been looking for ways to enhance a process known as exciton energy transfer, or EET, to create better solar cells as well as miniaturized photonic circuits which are dozens of times smaller than their silicon counterparts.

“Understanding the fundamental mechanisms of EET enhancement would alter the way we think about designing solar cells or the ways in which energy can be transported in nanoscale materials,” said Yuen-Zhou.

The drawback with EET, however, is that this form of energy transfer is extremely short-ranged, on the scale of only 10 nanometers, and quickly dissipates as the excitons interact with different molecules.

One solution to avoid those shortcomings is to hybridize excitons in a molecular crystal with the collective excitations within metals to produce plexcitons, which travel for 20,000 nanometers, a length which is on the order of the width of human hair.

Plexcitons are expected to become an integral part of the next generation of nanophotonic circuitry, light-harvesting solar energy architectures and chemical catalysis devices. But the main problem with plexcitons, said Yuen-Zhou, is that their movement along all directions, which makes it hard to properly harness in a material or device.

He and a team of physicists and engineers at MIT and Harvard found a solution to that problem by engineering particles called “topological plexcitons,” based on the concepts in which solid state physicists have been able to develop materials called “topological insulators.”

“Topological insulators are materials that are perfect electrical insulators in the bulk but at their edges behave as perfect one-dimensional metallic cables,” Yuen-Zhou said. “The exciting feature of topological insulators is that even when the material is imperfect and has impurities, there is a large threshold of operation where electrons that start travelling along one direction cannot bounce back, making electron transport robust. In other words, one may think about the electrons being blind to impurities.”

Plexcitons, as opposed to electrons, do not have an electrical charge. Yet, as Yuen-Zhou and his colleagues discovered, they still inherit these robust directional properties. Adding this “topological” feature to plexcitons gives rise to directionality of EET, a feature researchers had not previously conceived. This should eventually enable engineers to create plexcitonic switches to distribute energy selectively across different components of a new kind of solar cell or light-harvesting device.

Explore further: Topological insulators could exist in six new types not seen before, theorists predict

More information: Nature Communications, DOI: 10.1038/NCOMMS11783

Journal reference:Nature Communications

Provided by:University of California – San Diego

 

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UC San Diego: Targeted Drug Delivery with Nanoparticles = More Effective Medicines

Nanoparticles disguised as human platelets could greatly enhance the healing power of drug treatments for cardiovascular disease and systemic bacterial infections. These platelet-mimicking nanoparticles, developed by engineers at the University of California, San Diego, are capable of delivering drugs to targeted sites in the body — particularly injured blood vessels, as well as organs infected by harmful bacteria. Engineers demonstrated that by delivering the drugs just to the areas where the drugs were needed, these platelet copycats greatly increased the therapeutic effects of drugs that were administered to diseased rats and mice.

The research, led by nanoengineers at the UC San Diego Jacobs School of Engineering, was published online Sept. 16 in Nature.

“This work addresses a major challenge in the field of nanomedicine: targeted drug delivery with nanoparticles,” said Liangfang Zhang, a nanoengineering professor at UC San Diego and the senior author of the study. “Because of their targeting ability, platelet-mimicking nanoparticles can directly provide a much higher dose of medication specifically to diseased areas without saturating the entire body with drugs.”

Pseudocolored scanning electron microscope images of platelet-membrane-coated nanoparticles (orange) binding to the lining of a damaged artery (left) and to MRSA bacteria (right). Each nanoparticle is approximately 100 nanometers in diameter, which is one thousand times thinner than an average sheet of paper.

Credit: Zhang Research Group, UC San Diego Jacobs School of Engineering.

The study is an excellent example of using engineering principles and technology to achieve “precision medicine,” said Shu Chien, a professor of bioengineering and medicine, director of the Institute of Engineering in Medicine at UC San Diego, and a corresponding author on the study. “While this proof of principle study demonstrates specific delivery of therapeutic agents to treat cardiovascular disease and bacterial infections, it also has broad implications for targeted therapy for other diseases such as cancer and neurological disorders,” said Chien.

The ins and outs of the platelet copycats

On the outside, platelet-mimicking nanoparticles are cloaked with human platelet membranes, which enable the nanoparticles to circulate throughout the bloodstream without being attacked by the immune system. The platelet membrane coating has another beneficial feature: it preferentially binds to damaged blood vessels and certain pathogens such as MRSA bacteria, allowing the nanoparticles to deliver and release their drug payloads specifically to these sites in the body.

Enclosed within the platelet membranes are nanoparticle cores made of a biodegradable polymer that can be safely metabolized by the body. The nanoparticles can be packed with many small drug molecules that diffuse out of the polymer core and through the platelet membrane onto their targets.

To make the platelet-membrane-coated nanoparticles, engineers first separated platelets from whole blood samples using a centrifuge. The platelets were then processed to isolate the platelet membranes from the platelet cells. Next, the platelet membranes were broken up into much smaller pieces and fused to the surface of nanoparticle cores. The resulting platelet-membrane-coated nanoparticles are approximately 100 nanometers in diameter, which is one thousand times thinner than an average sheet of paper.

This cloaking technology is based on the strategy that Zhang’s research group had developed to cloak nanoparticles in red blood cell membranes. The researchers previously demonstrated that nanoparticles disguised as red blood cells are capable of removing dangerous pore-forming toxins produced by MRSA, poisonous snake bites and bee stings from the bloodstream.

By using the body’s own platelet membranes, the researchers were able to produce platelet mimics that contain the complete set of surface receptors, antigens and proteins naturally present on platelet membranes. This is unlike other efforts, which synthesize platelet mimics that replicate one or two surface proteins of the platelet membrane.

“Our technique takes advantage of the unique natural properties of human platelet membranes, which have a natural preference to bind to certain tissues and organisms in the body,” said Zhang. This targeting ability, which red blood cell membranes do not have, makes platelet membranes extremely useful for targeted drug delivery, researchers said.

Platelet copycats at work

In one part of this study, researchers packed platelet-mimicking nanoparticles with docetaxel, a drug used to prevent scar tissue formation in the lining of damaged blood vessels, and administered them to rats afflicted with injured arteries. Researchers observed that the docetaxel-containing nanoparticles selectively collected onto the damaged sites of arteries and healed them.

When packed with a small dose of antibiotics, platelet-mimicking nanoparticles can also greatly minimize bacterial infections that have entered the bloodstream and spread to various organs in the body. Researchers injected nanoparticles containing just one-sixth the clinical dose of the antibiotic vancomycin into one of group of mice systemically infected with MRSA bacteria. The organs of these mice ended up with bacterial counts up to one thousand times lower than mice treated with the clinical dose of vancomycin alone.

“Our platelet-mimicking nanoparticles can increase the therapeutic efficacy of antibiotics because they can focus treatment on the bacteria locally without spreading drugs to healthy tissues and organs throughout the rest of the body,” said Zhang. “We hope to develop platelet-mimicking nanoparticles into new treatments for systemic bacterial infections and cardiovascular disease.”

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Story Source:

The above post is reprinted from materials provided by University of California – San Diego. The original item was written by Liezel Labios. Note: Materials may be edited for content and length.

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Journal Reference:

1. Che-Ming J. Hu, Ronnie H. Fang, Kuei-Chun Wang, Brian T. Luk, Soracha Thamphiwatana, Diana Dehaini, Phu Nguyen, Pavimol Angsantikul, Cindy H. Wen, Ashley V. Kroll, Cody Carpenter, Manikantan Ramesh, Vivian Qu, Sherrina H. Patel, Jie Zhu, William Shi, Florence M. Hofman, Thomas C. Chen, Weiwei Gao, Kang Zhang, Shu Chien, Liangfang Zhang. Nanoparticle biointerfacing by platelet membrane cloaking. Nature, 2015; DOI: 10.1038/nature15373

Nano-Invisibility Cloaks get a Slimmer Design from Engineers at UC San Diego

Researchers have developed a new design for a cloaking device that overcomes some of the limitations of existing “invisibility cloaks.” In a new study, electrical engineers at the Univ. of California, San Diego have designed a cloaking device that is both thin and does not alter the brightness of light around a hidden object. The technology behind this cloak will have more applications than invisibility, such as concentrating solar energy and increasing signal speed in optical communications.

“Invisibility may seem like magic at first, but its underlying concepts are familiar to everyone. All it requires is a clever manipulation of our perception,” said Boubacar Kanté, a professor in the Dept. of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering and the senior author of the study. “Full invisibility still seems beyond reach today, but it might become a reality in the near future thanks to recent progress in cloaking devices.”

As their name implies, cloaks are devices that cover objects to make them appear invisible. The idea behind cloaking is to change the scattering of electromagnetic waves—such as light and radar—off an object to make it less detectable to these wave frequencies.

One of the drawbacks of cloaking devices is that they are typically bulky.

An extremely thin cloaking device is designed using dielectric materials. The cloak is a thin Teflon sheet (light blue) embedded with many small, cylindrical ceramic particles (dark blue). Image: Li-Yi Hsu/UC San Diego

“Previous cloaking studies needed many layers of materials to hide an object, the cloak ended up being much thicker than the size of the object being covered,” said Li-Yi Hsu, electrical engineering PhD student at UC San Diego and the first author of the study, which was recently published in Progress In Electromagnetics Research. “In this study, we show that we can use a thin single-layer sheet for cloaking.”

The researchers say that their cloak also overcomes another fundamental drawback of existing cloaking devices: being “lossy.” Cloaks that are lossy reflect light at a lower intensity than what hits their surface.

“Imagine if you saw a sharp drop in brightness around the hidden object, it would be an obvious telltale. This is what happens when you use a lossy cloaking device,” said Kanté. “What we have achieved in this study is a ‘lossless’ cloak. It won’t lose any intensity of the light that it reflects.”

Many cloaks are lossy because they are made with metal particles, which absorb light. The researchers report that one of the keys to their cloak’s design is the use of non-conductive materials called dielectrics, which unlike metals do not absorb light. This cloak includes two dielectrics, a proprietary ceramic and Teflon, which are structurally tailored on a very fine scale to change the way light waves reflect off of the cloak.

In their experiments, the researchers specifically designed a “carpet” cloak, which works by cloaking an object sitting on top of a flat surface. The cloak makes the whole system—object and surface—appear flat by mimicking the reflection of light off the flat surface. Any object reflects light differently from a flat surface, but when the object is covered by the cloak, light from different points is reflected out of sync, effectively cancelling the overall distortion of light caused by the object’s shape.

“This cloaking device basically fools the observer into thinking that there’s a flat surface,” said Kanté.

The researchers used Computer-Aided Design software with electromagnetic simulation to design and optimize the cloak. The cloak was modeled as a thin matrix of Teflon in which many small cylindrical ceramic particles were embedded, each with a different height depending on its position on the cloak.

“By changing the height of each dielectric particle, we were able to control the reflection of light at each point on the cloak,” explained Hsu. “Our computer simulations show how our cloaking device would behave in reality. We were able to demonstrate that a thin cloak designed with cylinder-shaped dielectric particles can help us significantly reduce the object’s shadow.”

“Doing whatever we want with light waves is really exciting,” said Kanté. “Using this technology, we can do more than make things invisible. We can change the way light waves are being reflected at will and ultimately focus a large area of sunlight onto a solar power tower, like what a solar concentrator does. We also expect this technology to have applications in optics, interior design and art.”

Source: Univ. of California, San Diego

 

At UC San Diego – Discovery Paves Way for new Kinds of Superconducting Electronics: Impacting Medicine, Physics, Materials Science and Satellite Communications

Physicists at UC San Diego have developed a new way to control the transport of electrical currents through high-temperature superconductors — materials discovered nearly 30 years ago that lose all resistance to electricity at commercially attainable low temperatures.

Their development, detailed in two separate scientific publications, paves the way for the development of sophisticated electronic devices capable of allowing scientists or clinicians to non-invasively measure the tiny magnetic fields in the heart or brain, and improve satellite communications.

‘We believe this new approach will have a significant and far-reaching impact in medicine, physics, materials science and satellite communications,’ said Robert Dynes, a professor of physics and former chancellor of UC San Diego. ‘It will enable the development of a new generation of superconducting electronics covering a wide spectrum, ranging from highly sensitive magnetometers for biomagnetic measurements of the human body to large-scale arrays for wideband satellite communications. In basic science, it is hoped it will contribute to the unravelling of the mysteries of unconventional superconductors and could play a major role in new technologies, such as quantum information science.’

The physicists used a helium ion beam to create an atomic scale Josephson junction (shown in the inset) in a crystal of Yttrium Barium Copper Oxide.

Credit: Meng Ma, UC San Diego

The research team headed by Dynes and Cybart, summarized its achievements in this week’s issue of Applied Physics Letters. Another paper outlining the initial discovery was published online April 27 in the journal Nature Nanotechnology.

The developments breathe new life into the promise of electronics constructed from ceramic materials that become superconducting — that is, lose all resistance to electricity — at temperatures that can be easily achieved in the laboratory with liquid nitrogen, which boils at 77 degrees Kelvin or 77 degrees above absolute zero.

Physicists first discovered high-temperature superconductivity in a copper-oxide materials in 1986, setting off an intense effort to develop new kinds of electronics and other devices with this new material.

‘Scientists and engineers worked with fervor to develop these new exciting materials, but soon discovered that they were much more complicated and difficult to work with than imagined,’ said Dynes. ‘These new materials demanded novel device architectures that proved very difficult to realize.’

The UC San Diego physicists found a way to control electrical transport through these materials by building a device within the superconducting material called a ‘Josephson junction,’ analogous in function to the transistor in semiconductor electronics. It’s composed of two superconducting electrodes separated by about one nanometer or a billionth of a meter.

‘Circuits built from Josephson junctions called Superconducting QUantum Interference Devices (SQUIDS), are used for detectors of extremely small magnetic fields, more than 10 billion times smaller than that of Earth,’ said Dynes. ‘One major drawback to these earlier devices is the low temperatures required for their operation, typically just 4 degrees above absolute zero. This requires intricate and costly cooling systems.’

‘Nearly three decades have passed since the discovery of the first high-temperature superconductor and progress in constructing electronic devices using these materials has been very slow because process control at the sub-10-nanometer scale is required to make high quality Josephson junctions out of these materials,’ he explained.

The UC San Diego physicists teamed up with Carl Zeiss Microscopy in Peabody, Mass., which has a facility capable of generating highly focused beams of helium ions, to experiment with an approach they believed might avoid previous problems.

‘Using the Zeiss Orion’s finely focused helium beam, we irradiated and hence disordered a nanoscale region of the superconductor to create what is called a ‘quantum mechanical tunnel barrier’ and were able to write Josephson circuits directly into a thin film of the oxide superconductor,’ said Shane Cybart, a physicist in Dynes’ laboratory who played a key role in the discoveries. ‘Using this direct-write method we eliminated the lithographic processing and offered the promise of a straightforward pathway to quantum mechanical circuits operating at more practical temperatures.’

‘The key to this method is that these oxide superconductors are very sensitive to the point defects in the crystal lattice caused by the ion beam. Increasing irradiation levels has the effect of increasing resistivity and reducing the superconducting transition temperature,’ said Cybart. ‘At very high irradiation levels the superconductor becomes insulating and no longer conducts or superconducts. This allows us to use the small helium beam to write these tunnel junctions directly into the material.’

The Nature Nanotechnology paper describes the development of the basic Josephson junction, while the Applied Physics Letters paper describes the development of the magnetic field sensor built from two junctions.

The UC San Diego physicists, who filed a patent application to license their discovery, are now collaborating with medical researchers to apply their work to the development of devices that can non-invasively measure the tiny magnetic fields generated within the brain, in order to study brain disorders such as autism and epilepsy in children.

‘In the communications field, we are developing wide bandwidth high data throughput satellite communications,’ said Cybart. ‘In basic science, we are using this technology to study ceramic superconducting materials to help determine the physics governing their operation which could lead to improved materials working at even higher temperatures.’

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Story Source:

The above post is reprinted from materials provided by University of California – San Diego. Note: Materials may be edited for content and length.

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Journal Reference:

1. E. Y. Cho, M. K. Ma, Chuong Huynh, K. Pratt, D. N. Paulson, V. N. Glyantsev, R. C. Dynes and Shane A. Cybart. YBa2Cu3O7− δ superconducting quantum interference devices with metallic to insulating barriers written with a focused helium ion beam. Applied Physics Letters, 2015 DOI: 10.1063/1.4922640

UC San Diego: Nano-Engineers Research Making Smart Clothing for Personalized Heating & Cooling

Imagine a fabric that will keep your body at a comfortable temperature—regardless of how hot or cold it actually is. That’s the goal of an engineering project at the University of California, San Diego, funded with a $2.6M grant from the U.S. Department of Energy’s Advanced Research Projects Agency – Energy (ARPA-E). Wearing this smart fabric could potentially reduce heating and air conditioning bills for buildings and homes.

The project, named ATTACH (Adaptive Textiles Technology with Active Cooling and Heating), is led by Joseph Wang, distinguished professor of nanoengineering at UC San Diego.

By regulating the temperature around an individual person, rather than a large room, the smart fabric could potentially cut the energy use of buildings and homes by at least 15 percent, Wang noted.

“In cases where there are only one or two people in a large room, it’s not cost-effective to heat or cool the entire room,” said Wang. “If you can do it locally, like you can in a car by heating just the car seat instead of the entire car, then you can save a lot of energy.”

Garment-based printable electrodes developed in the lab of Joseph Wang, distinguished professor of nanoengineering at UC San Diego, and lead principal investigator of ATTACH. (Image: Jacobs School of Engineering/UC San Diego)

The smart fabric will be designed to regulate the temperature of the wearer’s skin—keeping it at 93° F—by adapting to temperature changes in the room. When the room gets cooler, the fabric will become thicker. When the room gets hotter, the fabric will become thinner. To accomplish this feat, the researchers will insert polymers that expand in the cold and shrink in the heat inside the smart fabric.

“Regardless if the surrounding temperature increases or decreases, the user will still feel the same without having to adjust the thermostat,” said Wang.

“93° F is the average comfortable skin temperature for most people,” added Renkun Chen, assistant professor of mechanical and aerospace engineering at UC San Diego, and one of the collaborators on this project.

Chen’s contribution to ATTACH is to develop supplemental heating and cooling devices, called thermoelectrics, that are printable and will be incorporated into specific spots of the smart fabric. The thermoelectrics will regulate the temperature on “hot spots”—such as areas on the back and underneath the feet—that tend to get hotter than other parts of the body when a person is active.

“This is like a personalized air-conditioner and heater,” said Chen.

Saving energy

“With the smart fabric, you won’t need to heat the room as much in the winter, and you won’t need to cool the room down as much in the summer. That means less energy is consumed. Plus, you will still feel comfortable within a wider temperature range,” said Chen.

The researchers are also designing the smart fabric to power itself. The fabric will include rechargeable batteries, which will power the thermoelectrics, as well as biofuel cells that can harvest electrical power from human sweat. Plus, all of these parts—batteries, thermoelectrics and biofuel cells—will be printed using the technology developed in Wang’s lab to make printable wearable devices. These parts will also be thin, stretchable and flexible to ensure that the smart fabric is not bulky or heavy.

“We are aiming to make the smart clothing look and feel as much like the clothes that people regularly wear. It will be washable, stretchable, bendable and lightweight. We also hope to make it look attractive and fashionable to wear,” said Wang.

In terms of price, the team has not yet concluded how much the smart clothing will cost. This will depend on the scale of production, but the printing technology in Wang’s lab will offer a low-cost method to produce the parts. Keeping the costs down is a major goal, the researchers said.

The research team

Professor Joseph Wang, Department of NanoEngineering

Wang, the lead principal investigator of ATTACH, has pioneered the development of wearable printable devices, such as electrochemical sensors and temporary tattoo-based biofuel cells. He is the chair of the nanoengineering department and the director for the Center for Wearable Sensors at UC San Diego. His extensive expertise in printable, stretchable and wearable devices will be used here to make the proposed flexible biofuel cells, batteries and thermoelectrics.

Assistant Professor Renkun Chen, Department of Mechanical and Aerospace Engineering

Chen specializes in heat transfer and thermoelectrics. His research group works on physics, materials and devices related to thermal energy transport, conversion and management. His specialty in these areas will be used to develop the thermal models and the thermoelectric devices.

Associate Professor Shirley Meng, Department of NanoEngineering

Meng’s research focuses on energy storage and conversion, particularly on battery cell design and testing. At UC San Diego, she established the Laboratory for Energy Storage and Conversion and is the inaugural director for the Sustainable Power and Energy Center. Meng will develop the rechargeable batteries and will work on power integration throughout the smart fabric system.

Professor Sungho Jin, Department of Mechanical and Aerospace Engineering

Jin specializes in functional materials for applications in nanotechnology, magnetism, energy and biomedicine. He will design the self-responsive polymers that change in thickness based on changes in the surrounding temperature.

Dr. Joshua Windmiller, CEO of Electrozyme LLC

Windmiller, former Ph.D. student and postdoc in Wang’s nanoengineering lab, is an expert in printed biosensors, bioelectronics and biofuel cells. He co-founded Electrozyme LLC, a startup devoted to the development of novel biosensors for application in the personal wellness and healthcare domains. Electrozyme will serve as the industrial partner for ATTACH and will lead the efforts to test the smart fabric prototype and bring the technology into the market.

Source: UC San Diego

New Solar Power Material Converts 90 Percent of Captured Light into Heat

October 29, 2014

A multidisciplinary engineering team developed a new nanoparticle-based material for concentrating solar power plants designed to absorb and convert to heat more than 90 percent of the sunlight it captures. The new material can also withstand temperatures greater than 700 degrees Celsius and survive many years outdoors in spite of exposure to air and humidity.

A multidisciplinary engineering team at the University of California, San Diego developed a new nanoparticle-based material for concentrating solar power plants designed to absorb and convert to heat more than 90 percent of the sunlight it captures. The new material can also withstand temperatures greater than 700 degrees Celsius and survive many years outdoors in spite of exposure to air and humidity. Their work, funded by the U.S. Department of Energy’s SunShot program, was published recently in two separate articles in the journal Nano Energy.

By contrast, current solar absorber material functions at lower temperatures and needs to be overhauled almost every year for high temperature operations.

“We wanted to create a material that absorbs sunlight that doesn’t let any of it escape. We want the black hole of sunlight,” said Sungho Jin, a professor in the department of Mechanical and Aerospace Engineering at UC San Diego Jacobs School of Engineering. Jin, along with professor Zhaowei Liu of the department of Electrical and Computer Engineering, and Mechanical Engineering professor Renkun Chen, developed the Silicon boride-coated nanoshell material. They are all experts in functional materials engineering.

Graduate student Bryan VanSaders measures how much simulated sunlight a novel material can absorb using a unique set of instruments that takes spectral measurements from visible to infrared. This testing is led by electrical engineering professor Zhaowei Liu.

Credit: David Baillot/UC San Diego Jacobs School of Engineering.

[Click to enlarge image]

The novel material features a “multiscale” surface created by using particles of many sizes ranging from 10 nanometers to 10 micrometers. The multiscale structures can trap and absorb light which contributes to the material’s high efficiency when operated at higher temperatures.

Concentrating solar power (CSP) is an emerging alternative clean energy market that produces approximately 3.5 gigawatts worth of power at power plants around the globe — enough to power more than 2 million homes, with additional construction in progress to provide as much as 20 gigawatts of power in coming years. One of the technology’s attractions is that it can be used to retrofit existing power plants that use coal or fossil fuels because it uses the same process to generate electricity from steam.

Traditional power plants burn coal or fossil fuels to create heat that evaporates water into steam. The steam turns a giant turbine that generates electricity from spinning magnets and conductor wire coils. CSP power plants create the steam needed to turn the turbine by using sunlight to heat molten salt. The molten salt can also be stored in thermal storage tanks overnight where it can continue to generate steam and electricity, 24 hours a day if desired, a significant advantage over photovoltaic systems that stop producing energy with the sunset.

One of the most common types of CSP systems uses more than 100,000 reflective mirrors to aim sunlight at a tower that has been spray painted with a light absorbing black paint material. The material is designed to maximize sun light absorption and minimize the loss of light that would naturally emit from the surface in the form of infrared radiation.

The UC San Diego team’s combined expertise was used to develop, optimize and characterize a new material for this type of system over the past three years. Researchers included a group of UC San Diego graduate students in materials science and engineering, Justin Taekyoung Kim, Bryan VanSaders, and Jaeyun Moon, who recently joined the faculty of the University of Nevada, Las Vegas. The synthesized nanoshell material is spray-painted in Chen’s lab onto a metal substrate for thermal and mechanical testing. The material’s ability to absorb sunlight is measured in Liu’s optics laboratory using a unique set of instruments that takes spectral measurements from visible light to infrared.

Current CSP plants are shut down about once a year to chip off the degraded sunlight absorbing material and reapply a new coating, which means no power generation while a replacement coating is applied and cured. That is why DOE’s SunShot program challenged and supported UC San Diego research teams to come up with a material with a substantially longer life cycle, in addition to the higher operating temperature for enhanced energy conversion efficiency. The UC San Diego research team is aiming for many years of usage life, a feat they believe they are close to achieving.

Modeled after President Kennedy’s moon landing program that inspired widespread interest in science and space exploration, then-Energy Secretary Steven P. Chu launched the Sunshot Initiative in 2010 with the goal of making solar power cost competitive with other means of producing electricity by 2020.

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The above story is based on materials provided by University of California – San Diego. Note: Materials may be edited for content and length.