Robots With The Sense Of Touch

A team of researchers from the University of Houston (UH) has reported a breakthrough in stretchable electronics that can serve as an artificial skin, allowing a robotic hand to sense the difference between hot and cold, while also offering advantages for a wide range of biomedical devices.

Cunjiang Yu, Bill D. Cook Assistant Professor of mechanical engineering and lead author for the paper, said the work is the first to create a semiconductor in a rubber composite format, designed to allow the electronic components to retain functionality even after the material is stretched by 50 percent. The semiconductor in rubber composite format enables stretchability without any special mechanical structure. Yu noted that traditional semiconductors are brittle and using them in otherwise stretchable materials has required a complicated system of mechanical accommodations. “That’s both more complex and less stable than the new discovery, as well as more expensive.”

Our strategy has advantages for simple fabrication, scalable manufacturing, high-density integration, large strain tolerance and low cost,” he said.

Yu and the rest of the team – co-authors include first author Hae-Jin Kim, Kyoseung Sim and Anish Thukral, all with the UH Cullen College of Engineering – created the electronic skin and used it to demonstrate that a robotic hand could sense the temperature of hot and iced water in a cup. The skin also was able to interpret computer signals sent to the hand and reproduce the signals as .

The robotic skin can translate the gesture to readable letters that a person like me can understand and read,” Yu said.

The work is reported in the journal Science Advances.


Cheap, Robust Catalyst Splits Water Into Hydrogen And Oxygen

Splitting water into hydrogen and oxygen to produce clean energy can be simplified with a single catalyst developed by scientists at Rice University and the University of Houston. The electrolytic film produced at Rice and tested at Houston is a three-layer structure of nickel, graphene and a compound of iron, manganese and phosphorus. The foamy nickel gives the film a large surface, the conductive graphene protects the nickel from degrading and the metal phosphide carries out the reactionRice chemist Kenton Whitmire and Houston electrical and computer engineer Jiming Bao and their labs developed the film to overcome barriers that usually make a catalyst good for producing either oxygen or hydrogen, but not both simultaneously.

A catalyst developed by Rice University and the University of Houston splits water into hydrogen and oxygen without the need for expensive metals like platinum. This electron microscope image shows nickel foam coated with graphene and then the catalytic surface of iron, manganese and phosphorus

Regular metals sometimes oxidize during catalysis,” Whitmire said. “Normally, a hydrogen evolution reaction is done in acid and an oxygen evolution reaction is done in base. We have one material that is stable whether it’s in an acidic or basic solution.

The discovery builds upon the researchers’ creation of a simple oxygen-evolution catalyst revealed earlier this year. In that work, the team grew a catalyst directly on a semiconducting nanorod array that turned sunlight into energy for solar water splittingElectrocatalysis requires two catalysts, a cathode and an anode. When placed in water and charged, hydrogen will form at one electrode and oxygen at the other, and these gases are captured. But the process generally requires costly metals to operate as efficiently as the Rice team’s catalyst.

The standard for hydrogen evolution is platinum,” Whitmire explained. “We’re using Earth-abundant materials — iron, manganese and phosphorus — as opposed to noble metals that are much more expensive.

The robust material is the subject of a paper in Nano Energy.


Clean Renewable Source Of Hydrogen Fuel For Electric Car

Rice University scientists have created an efficient, simple-to-manufacture oxygen-evolution catalyst that pairs well with semiconductors for solar water splitting, the conversion of solar energy to chemical energy in the form of hydrogen and oxygen.

anode RiceA photo shows an array of titanium dioxide nanorods with an even coating of an iron, manganese and phosphorus catalyst. The combination developed by scientists at Rice University and the University of Houston is a highly efficient photoanode for artificial photosynthesis. Click on the image for a larger version

The lab of Kenton Whitmire, a Rice professor of chemistry, teamed up with researchers at the University of Houston and discovered that growing a layer of an active catalyst directly on the surface of a light-absorbing nanorod array produced an artificial photosynthesis material that could split water at the full theoretical potential of the light-absorbing semiconductor with sunlight. An oxygen-evolution  catalyst splits water into hydrogen and oxygen. Finding a clean renewable source of hydrogen fuel is the focus of extensive research, but the technology has not yet been commercialized.

The Rice team came up with a way to combine three of the most abundant metalsiron, manganese and phosphorus — into a precursor that can be deposited directly onto any substrate without damaging it. To demonstrate the material, the lab placed the precursor into its custom chemical vapor deposition (CVD) furnace and used it to coat an array of light-absorbing, semiconducting titanium dioxide nanorods. The combined material, called a photoanode, showed excellent stability while reaching a current density of 10 milliamps per square centimeter, the researchers reported.

The results appear in two new studies. The first, on the creation of the films, appears in Chemistry: A European Journal. The second, which details the creation of photoanodes, appears in ACS Nano.


Solar Cells : How To Boost Efficiency Up To 30%

Researchers from the University of Houston have reported the first explanation for how a class of materials changes during production to more efficiently absorb light, a critical step toward the large-scale manufacture of better and less-expensive solar panels. The work, published this month as the cover story for Nanoscale, offers a mechanism study of how a perovskite thin film changes its microscopic structure upon gentle heating, said Yan Yao, assistant professor of electrical and computer engineering and lead author on the paper. This information is crucial for designing a manufacturing process that can consistently produce high-efficiency solar panels.

Perovskite cheap

Last year Yao and other researchers identified the crystal structure of the non-stoichiometric intermediate phase as the key element for high-efficiency perovskite solar cells. But what happened during the later thermal annealing step remained unclear. The work is fundamental science, Yao said, but critical for processing more efficient solar cells.

Otherwise, it’s like a black box,” he said. “We know certain processing conditions are important, but we don’t know why.”

The work also yielded a surprise: the materials showed a peak efficiency – the rate at which the material converted light to electricity – before the intermediate phase transformation was complete, suggesting a new way to produce the films to ensure maximum efficiency. Yao said researchers would have expected the highest efficiency to come after the material had been converted to 100 percent perovskite film. Instead, they discovered the best-performing solar devices were those for which conversion was stopped at 18 percent of the intermediate phase, before full conversion.

We found that the phase composition and morphology of solvent engineered perovskite films are strongly dependent on the processing conditions and can significantly influence photovoltaic performance,” the researchers wrote. “The strong dependence on processing conditions is attributed to the molecular exchange kinetics between organic halide molecules and DMSO (dimethyl sulfoxide) coordinated in the intermediate phase.

Perovskite compounds commonly are comprised of a hybrid organic-inorganic lead or tin halide-based material and have been pursued as potential materials for solar cells for several years. Yao said their advantages include the fact that the materials can work as very thin films – about 300 nanometers, compared with between 200 and 300 micrometers for silicon wafers, the most commonly used material for solar cells. Perovskite solar cells also can be produced by solution processing at temperatures below 150 degrees Centigrade (about 300 degrees Fahrenheit) making them relatively inexpensive to produce.

At their best, perovskite solar cells have an efficiency rate of about 22 percent, slightly lower than that of silicon (25 percent). But the cost of silicon solar cells is also dropping dramatically, and perovskite cells are unstable in air, quickly losing efficiency. They also usually contain lead, a toxin.

Still, Yao said, the materials hold great promise for the solar industry, even if they are unlikely to replace silicon entirely. Instead, he said, they could be used in conjunction with silicon, boosting efficiency to 30 percent or so.


Nanotechnology Boosts Oil Recovery

As oil producers struggle to adapt to , getting as much oil as possible out of every well has become even more important, despite concerns from nearby residents that some chemicals used to boost production may pollute underground water resources.

Researchers from the University of Houston have reported the discovery of a nanotechnology-based solution that could address both issues – achieving 15 percent tertiary oil recovery at low cost, without the large volume of chemicals used in most commercial fluids. The solution – graphene-based Janus amphiphilic nanosheets – is effective at a concentration of just 0.01 percent, meeting or exceeding the performance of both conventional and other nanotechnology-based fluids, said Zhifeng Ren, MD Anderson Chair professor of physics. Janus nanoparticles have at least two physical properties, allowing different chemical reactions on the same particle.

The low concentration and the high efficiency in boosting tertiary oil recovery make the nanofluid both more environmentally friendly and less expensive than options now on the market, said Ren, who also is a principal investigator at the Texas Center for Superconductivity at UH. He is lead author on a paper describing the work, published June 27 in the Proceedings of the National Academy of Sciences.

oil well

Our results provide a novel nanofluid flooding method for tertiary oil recovery that is comparable to the sophisticated chemical methods,” they wrote. “We anticipate that this work will bring simple nanofluid flooding at low concentration to the stage of oilfield practice, which could result in oil being recovered in a more environmentally friendly and cost-effective manner.

The U.S. Department of Energy estimates as much as 75 percent of recoverable reserves may be left after producers capture hydrocarbons that naturally rise to the surface or are pumped out mechanically, followed by a secondary recovery process using water or gas injection.

Traditional “tertiaryrecovery involves injecting a chemical mix into the well and can recover between 10 percent and 20 percent, according to the authors. But the large volume of chemicals used in tertiary oil recovery has raised concerns about potential environmental damage.

Obviously simple nanofluid flooding (containing only nanoparticles) at low concentration (0.01 wt% or less) shows the greatest potential from the environmental and economic perspective,” the researchers wrote.

Previously developed simple nanofluids recover less than 5 percent of the oil when used at a 0.01 percent concentration, they reported. That forces oil producers to choose between a higher nanoparticle concentration – adding to the cost – or mixing with polymers or surfactants. In contrast, they describe recovering 15.2 percent of the oil using their new and simple nanofluid at that concentration – comparable to chemical methods and about three times more efficient than other nanofluids.


How To Kill Bacteria Using Gold Nanoparticles And Light

Researchers have developed a new technique for killing bacteria in seconds using highly porous gold nanodisks and light. The method could one day help hospitals treat some common infections without using antibiotics, which could help reduce the risk of spreading antibiotics resistance.

killing bacteriaWe showed that all of the bacteria were killed pretty quickly . . . within 5 to 25 seconds. That’s a very fast process,” said corresponding author Wei-Chuan Shih, a professor in the electrical and computer engineering department, University of Houston, Texas.

Scientists create gold nanoparticles in the lab by dissolving gold, reducing the metal into smaller and smaller disconnected pieces until the size must be measured in nanometers. One nanometer equals a billionth of a meter. A human hair is between 50,000 to 100,000 nanometers in diameter. Once miniaturized, the particles can be crafted into various shapes including rods, triangles or disks.

Previous research shows that gold nanoparticles absorb light strongly, converting the photons quickly into heat and reaching temperatures hot enough to destroy various types of nearby cells – including cancer and bacterial cells.

The research has been published in Optical Materials Express, a journal published by The Optical Society

New Cheap Catalyst To Produce Hydrogen From Water

Graphene doped with nitrogen and augmented with cobalt atoms has proven to be an effective, durable catalyst for the production of hydrogen from water, according to scientists at Rice University. The Rice lab of chemist James Tour and colleagues at the Chinese Academy of Sciences, the University of Texas at San Antonio and the University of Houston have reported the development of a robust, solid-state catalyst that shows promise to replace expensive platinum for hydrogen generation.

Tucson fuel cell

Catalysts can split water into its constituent hydrogen and oxygen atoms, a process required for fuel cells. Hydrogen electric cars as the Tucson from Hyundai are powered by fuel cells.
The latest discovery, detailed in Nature Communications, is a significant step toward lower-cost catalysts for energy production, according to the researchers.

What’s unique about this paper is that we show not the use of metal particles, not the use of metal nanoparticles, but the use of atoms,” Tour said. “The particles doing this chemistry are as small as you can possibly get.
We’re getting away with very little cobalt to make a catalyst that nearly matches the best platinum catalysts.” In comparison tests, he said the new material nearly matched platinum’s efficiency to begin reacting at a low onset voltage, the amount of electricity it needs to begin separating water into hydrogen and oxygen.


How To Extract Molecules From Live Cells

University of Houston (UH) researchers have devised a new method for extracting molecules from live cells without disrupting cell development, work that could provide new avenues for the diagnosis of cancer and other diseases. The researchers used magnetized carbon nanotubes to extract biomolecules from live cells, allowing them to retrieve molecular information without killing the individual cells.

Most current methods of identifying intracellular information result in the death of the individual cells, making it impossible to continue to gain information and assess change over time, said Zhifeng Ren, M.D. Anderson Chair professor of physics and principal investigator at the Center for Superconductivity at UH and lead author of the paper. The work was a collaboration between Ren’s lab and that of Paul Chu, T.L.L. Temple Chair of Science and founding director of the Texas Center for Superconductivity.
Other key researchers on the project included Xiaoliu Zhang, a cancer researcher with the UH Center for Nuclear Receptors and Cell Signaling, and Dong Cai, assistant professor of physics. Chu, a co-author of the paper, said the new technique will allow researchers to draw fundamental information from a single cell.
Now, (most) techniques break up many cells to extract the material inside the cells, so what you get is the average over many cells,” Zhifeng Ren said. “The individual cells may be different, but you cannot see exactly how they function.

A description of the work appears this week in the Proceedings of the National Academy of Sciences.

New Efficient Nanoparticle Solar Panel Coat

Solar panels need to have a clean surface to efficiently gather light from the sun, but they are often soiled by dust, pollen, water and other particles. A University of Houston researcher has developed a nanoparticle coating for solar panels that makes it easier to keep the panels clean, which helps maintain their efficiency and reduces the maintenance and operations costs. The patent-pending coating developed by physics professor Seamus “Shay” Curran, director of UH’s Institute for NanoEnergy, has successfully undergone testing at the Dublin Institute for Technology and will undergo field trials being conducted by an engineering firm in North Carolina.
Curran said the June testing in Ireland and the field trials being done at Livingston & Haven in Charlotte, N.C., represent significant steps forward in moving the coating and a related technology to the marketplace.

The Self-Cleaning Nano Hydrophobic (SCNH107TM) layer has been licensed by C-Voltaics from UH. C-Voltaics, a start-up energy company dedicated to the generation of more practical clean energy for use in off-grid and on-grid applications.