Other materials stories that may be of interestPublished on May 7th, 2013 | By: Eileen De Guire
Chemical engineering researchers have identified a new mechanism to convert natural gas into energy up to 70 times faster, while effectively capturing the greenhouse gas carbon dioxide. “This could make power generation from natural gas both cleaner and more efficient,” says Fanxing Li, coauthor of a paper on the research and an assistant professor of chemical and biomolecular engineering at North Carolina State University. At issue is a process called chemical looping, in which a solid, oxygen-laden material—called an “oxygen carrier”—is put in contact with natural gas. The oxygen atoms in the oxygen carrier interact with the natural gas, causing combustion that produces energy. Previous state-of-the-art oxygen carriers were made from a composite of inert ceramic material and metal oxides. But Li’s team has developed a new type of oxygen carrier that include a “mixed ionic-electronic conductor,” which effectively shuttles oxygen atoms into the natural gas very efficiently—making the chemical looping combustion process as much as 70 times faster. This mixed conductor material is held in a nanoscale matrix with an iron oxide. The oxide serves as a source of oxygen for the mixed conductor to shuttle out into the natural gas. In addition to energy, the combustion process produces water vapor and CO2. By condensing out the water vapor, researchers are able to create a stream of concentrated CO2 to be captured for sequestration.
Over 20 million people in Europe suffer from osteoarthritis, which can lead to extensive damage to the knee and hip cartilage. Stem cells offer a promising way forward but a key challenge has been to design a ‘smart material’ that is biologically effective for cartilage tissue regeneration. Now researchers have identified a blend of naturally occurring fibers such as cellulose and silk that makes progress towards affordable and effective cell-based therapy for cartilage repair a step closer. The EPSRC-funded study, published in Biomacromolecules and undertaken by University of Bristol (UK) researchers, explored the feasibility of using natural fibers such as silk and cellulose as stem cell scaffolds—the matrix to which stem cells can cling to as they grow. Both cellulose and silk are commonly used in textiles but the researchers demonstrated an unexpected use for the two natural polymers when mixed with stem cells. The team treated blends of silk and cellulose for use as a tiny scaffold that allows adult connective tissue stem cells to form into preliminary form of chondrocytes—the cells that make healthy tissue cartilage – and secrete extracellular matrix similar to natural cartilage. Wael Kafienah, lead author from the University’s School of Cellular and Molecular Medicine, says, “We were surprised with this finding, the blend seems to provide complex chemical and mechanical cues that induce stem cell differentiation into preliminary form of chondrocytes without need for biochemical induction using expensive soluble differentiation factors. This new blend can cut the cost for health providers and makes progress towards effective cell-based therapy for cartilage repair a step closer.”
Researchers from Ulsan National Institute of Science and Technology (UNIST) demonstrated high-performance polymer solar cells (PSCs) with power conversion efficiency (PCE) of 8.92 percent, which are the highest values reported to date for plasmonic PSCs using metal nanoparticles (NPs). Compared to silicon-based devices, PSCs are lightweight (which is important for small autonomous sensors), solution processability (potentially disposable), inexpensive to fabricate (sometimes using printed electronics), flexible, and customizable on the molecular level, and they have lower potential for negative environmental impact. Polymer solar cells have attracted a lot of interest due to these many advantages. Although these many advantages, PSCs currently suffer from a lack of enough efficiency for large scale applications and stability problems but their promise of extremely cheap production and eventually high efficiency values has led them to be one of the most popular fields in solar cell research. The research team employed the surface plasmon resonance effect via multi-positional silica-coated silver NPs to increase light absorption.
Preterm infants appear to mature better if they are shielded from most wavelengths of visible light, from violet to orange. But it has been a challenge to develop a controllable light filter for preterm incubators that can switch between blocking out all light—for sleeping—and all but red light to allows medical staff and parents to check up on the kids when they’re awake. Now, in a paper accepted for publication in Applied Physics Letters, researchers describe a proof-of-concept mirror that switches between reflective and red-transparent states when a small voltage is applied. The research team had previously identified a magnesium-iridium reflective thin film that transforms into a red-transparent state when it incorporates protons. Providing those protons in a way that is practical for preterm incubators, however, was the challenge. The typical method—using dilute hydrogen gas—is unacceptable in a hospital setting. So the team created a stack of thin films that includes both an ion storage layer and the magnesium-iridium layer: a voltage drives protons from the ion storage layer to the magnesium-iridium layer, transforming it into its red-transparent state. Reversing the voltage transforms it back into a reflective mirror. The researchers report that the device still allows some undesirable light wavelengths through, but a force of just 5 volts changes the device’s state in as little as 10 seconds. The researchers are now looking at other materials to improve color filtering and switching speed.
Simpleware, a company set up to commercialize EPSRC-supported research at the University of Exeter, has won The Queen’s Award for Enterprise in the International Trade Category. Founded in 2003 by Philippe Young, the company’s pioneering software converts 3D image data into high-quality computer models used for engineering design and simulation. The technology has been applied across a host of disciplines and industries—from mobile phones to car engines; asphalt damage to back pain, contact lenses to hearing aids. The software is underpinned by patented techniques developed and improved with the aid of EPSRC funding to produce a previously unattainable level of realism in 3D simulations. Since 2008, Simpleware’s exports have seen an overseas sales growth of 690 percent. The company’s global export markets include the United States, Germany, Japan, France, China, Australia, Canada and other EU countries. Strong re-selling networks are also being established in India, Taiwan, and Singapore. The majority of sales are to blue-chip companies, research institutes and universities world-wide, including NASA and the Naval Research Laboratory. Young says, “The ability to generate robust and accurate numerical models from various sources of image data has started a revolution in the world of multi-physics simulation.
University of Illinois researchers have developed a new way to produce highly uniform nanocrystals used for both fundamental and applied nanotechnology projects. “We have developed a unique approach for the synthesis of highly uniform icosahedral nanoparticles made of platinum,” explains Hong Yang, a professor of chemical and biomolecular engineering and a faculty affiliate at the Center for Nanoscale Science and Technology at Illinois. “This is important both in fundamental studies-nanoscience and nanotechnology-and in applied sciences such as high performance fuel cell catalysts. Yang’s research group focuses on the synthesis and understanding structure-property relationship of nanostructured materials for applications in energy, catalysis, and biotechnology. “Although polyhedral nanostructures, such as a cube, tetrahedron, octahedron, cuboctahedron, and even icosahedron, have been synthesized for several noble metals, uniform Pt icosahedra do not form readily and are rarely made,” states Wei Zhou, a visiting scholar with Yang’s research group. An icosahedron crystal is a polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. According to Yang, icosahedral shaped crystals can improve the catalytic activity in oxygen reduction reaction partly because of the surface strain. “The key reaction step to improve the activity of oxygen electrode catalysts in the hydrogen fuel cell is to optimize the bond strength between Pt and absorbed oxygen-containing intermediate species,” Yang says. “This allows the rapid production of water and let the intermediate react and leave the surface quickly so the catalyst site can be used again.”
A team led by Professor Keon Jae Lee from the Department of Materials Science and Engineering at KAIST has developed in vivo silicon-based flexible large-scale integrated circuits (LSI) for biomedical wireless communication. Silicon-based semiconductors have played significant roles in signal processing, nerve stimulation, memory storage, and wireless communication in implantable electronics. However, the rigid and bulky LSI chips have limited uses in in vivo devices due to incongruent contact with the curvilinear surfaces of human organs. Although several research teams have fabricated flexible integrated circuits (ICs, tens of interconnected transistors) on plastics, their inaccurate nanoscale alignment on plastics has restricted the demonstration of flexible nanotransistors and their large-scale interconnection for in vivo LSI applications such as main process unit, high-density memory and wireless communication. Professor Keon Jae Lee’s team fabricated radio frequency integrated circuits interconnected with thousand nanotransistors on silicon wafer by state-of-the-art CMOS process, and then they removed the entire bottom substrate except top 100 nm active circuit layer by wet chemical etching.
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