F]EUJS

Fuel cells an attractive alternative The energy crisis in California focused attention at the American Chemical Society conference on fuel cells. With energy-producing efficiencies on a par with internal combustion engines and better than batteries, fuel cells are potentially attractive for many applications - such as powering vehicles - where their small size, light weight and low environmental impact are very attractive. Hydrogen is the key ingredient - when passed through a proton exchange membrane (PEM], it combines with oxygen releasing energy and producing water as a bi-product. However, the characteristics and stability of the polymeric materials used for PEMs are limiting realization of workable fuel cells. James E. McGrath from Virginia Tech is working on many of the problems that

need answers. Using hetropolyacids (HPAs), McGrath has developed nanocomposite PEM materials that can be used at high temperatures. His research teem has also determined how to increase ion-conducting component of PEMs without weakening the polymer. "We are trying to see if we can fool mother nature," explains McGreth. "It appears that constructing block co-polymers will allow us to control the conductivity and morphology of the material - to increase the conductive monomer without weakening the total polymer strength." Overall, this is allowing the researchers to develop a methodology that relates PEM performance in a fuel cell to the intrinsic properties of the polymer. Alternative technologies, such as carbonate and alkaline fuel

cells, were also discussed, with the Solid State Energy Conversion Alliance's presenting its plans for development of solid oxide (all ceramic) fuel cells over the next 5-15 years. But despite the positive innovations, researchers from the University of California, Berkeley, paint a more disturbing picture. Funding of energy technology research has declined throughout the industrial world over the last 20 years, say Antonia Herzog and co-workers, and in particular, a "significant and sustained pattern of under- investment in the US energy sector." Not only does such under-funding impact the ability to deal with such environmental problems like global warming, but also say the researchers, the overall global energy economy.

Living chips Two reports bring the reality of hybrid 'living' devices closer. Gunther Zeck and Peter Frcmherz at the Max Planck Institute for Biochemistry have created a circuit from living neurons [PNAS (2001) 98 10445-10450]. Extracted from pond snails, neurons were grown on a silicon chip to form synaptic connections. An applied voltage signal traversed the neuronal net and returned to the chip. Bruce Wheeler, presenting at a recent conference, also borrows from microelectronics to grow nerve cells. The University of Illinois researcher uses a lithographic technique, micros'tamPing, to pattern glass substrates with the cell culture media polylysine. When rat nerve cells are introduced, "the cells soon mature and begin sending electrical signals," says Wheeler.

Improving on nature Researchers from Cornell University told the American Chemical Society conference how they are developing a polymer that mimics - and improves upon - nature. Starting with silk - which has a

crystalline structure consisting of a regular protein-folding pattern induced by its amino acids - Dotsevi Sogah created a molecular hybrid from natural and synthetic molecules block by block. Using 'a bimolecular Lego set' the researchers combined molecules from silk with a range of synthetic ones, including polypropylene oxide,

polyethylene and nylon, in a hard-soft sequence. The novel materials are very flexible, strong and water soluble - potentially ideal for a range of applications from textiles, for bandages or even bulletproof vests, to drug delivery systems, says Sogah. The next step is to apply the 'Lego set' approach to other materials to mimic collagen and teeth-hardening proteins. '~Ve want to understand the principles behind this so we can dial into the properties we want," explains Sogah. "We are trying to improve on nature."

Mimicking the body's defense Medical implants can carry a serious risk of infection. Now researchers have found a way to mimic the body's own self- defense mechanisms to address the problem. Researchers at the University of North Carolina at Chapel Hill led by Mark Schoenfisch have developed a sol-gel based material infused with nitric oxide which could be used to coat implanted devices. "During a process called phagocytosis, immune cells engulf bacteria and release high levels of reactive molecules, including nitric oxide, to destroy these foreign

cells," explains Schoenfisch. "We hypothesized that polymeric nitric oxide release might represent a new approach for reducing bacterial adhesion and possibly the incidence or severity of infection." Thin-films of aminosilane-based sol-gels were prepared on glass slides, which were then exposed to high pressures of nitric oxide gas. Once in a watery environment, such as blood or tissue, nitric oxide is slowly released over a period of days. Web edition of the Journal of the American Chemical Society: http'7/pubs.acs.org/jou mals/j a csat/

14 ~ September/October 2001