Interesting tech developments in nanotech, nanostructured materials, etc.
Ken Novak's Weblog
Thursday, September 11, 2003
Sandia Nanocrystal Research Unraveling Nature's Secrets: ""Biominerals" is the term the team uses to describe complex natural materials that are composed of simple minerals, such as calcium, but that are organized in complex three-dimensional nanostructures. The team's first thrust was to uncover the mechanisms by which such complex crystals are induced into growing at selected sites. For instance, the biominerals in both macroscopic seashells and microscopic diatoms are synthesized in nature when the organism extracts dissolved ions of calcium and silicate from ocean water and uses proteins to reorganize them into nanostructures. "We've found that nature uses protein molecules to precisely control the orientation and morphology of biominerals. As a result, these materials are much stronger than normal man-made versions," said Voigt. .. 10:12:29 PM
Using computer models, the team designed simple experiments using organic molecules that bind to crystals, thereby directing and controlling their growth. By proving the concept in that way, Liu's team embarked on the long journey toward understanding how nature directs organic growth and translating that into a set of general rules guiding the manufacturing of atomically perfect nanomaterials. Currently the team is codifying its findings into a set of laboratory tools for controlling the delivery, diffusion and transport of the chemical "species" in its aqueous reaction chambers. The team plans to leverage Sandia's microfluidic platforms to provide a precise mechanism for altering the parameters of its experiments. The team predicts that its findings will result in manufacturing methodologies that are environmentally benign but that enable superior nanoparticles, nanowires and complexly nanostructured films. "
Booze to Fuel Gadget Batteries: St Louis University researchers create an alchohol-powered fuel cell using enzymes. "The team behind the new battery has produced a constant current from its biofuel cell that is still going strong after two months. .. Prior experiments have used methanol, another type of alcohol, as fuel. The Saint Louis team chose ethanol. "A big advantage is that ethanol is not toxic like methanol, so it is easier to deal with," said team leader and assistant professor of chemistry Shelley Minteer. ..
"The enzymes we use are called dehydrogenase," Akers said. "We chose these because they strip protons from alcohol, and this is the reaction we need to get electricity." Enzymes are not alive like cells or bacteria, but they have to be active for the biofuel cell to work. Keeping the sensitive catalysts active has caused problems in the past. "Enzymes are fairly fragile and can be denatured if there are any changes in temperature or in the pH level (acidity or alkalinity)," Minteer said. .. Minteer and her team overcame this conundrum by coating the biofuel cell's electrodes with a polymer that contains tailored micelles, or pores, which provide an ideal microenvironment for the enzymes to thrive. ..
Minteer said the team is working on ways to increase their biofuel cell's power density. Currently the team's battery can produce 2 milliwatts of power per effective square centimeter. The average cell phone requires 500 milliwatts to operate. The team is also looking at ways to produce a battery designed to fit today's portables that can also produce the necessary power output. "It's like a radiator in car," Akers said. "It's folded, and all those ridges and folds give it a high surface area so the effective surface area becomes tremendously huge. You can do this on a micro scale so that the effective surface area of the electrodes is enormous. This is what we are doing in the designing process."
Akers is confident the team will have a working prototype in a year, and that the finished product will hit store shelves a year later. " 9:53:47 PM
New technique for organic solar cells
: "researchers have pursued organic photovoltaic films for many years, but have been plagued with problems of efficiency, said [Princeton researcher] Forrest. The first organic solar cell, developed in 1986, was 1 percent efficient -- that is, it converted only 1 percent of the available light energy into electrical energy. "And that number stood for about 15 years," said Forrest.
Forrest and colleagues recently broke that barrier by changing the organic compounds used to make their solar cells, yielding devices with efficiencies of more than 3 percent. The most recent advance reported in Nature involves a new method for forming the organic film, which increased the efficiency by 50 percent. Researchers in Forrest's lab are now planning to combine the new materials and techniques. Doing so could yield at least 5 percent efficiency, which would make the technology attractive to commercial manufacturers. With further commercial development, organic solar devices would be viable in the marketplace with 5 to 10 percent efficiency, the researchers estimated. "We think we have pathway for using this and other tricks to get to 10 percent reasonably quickly," Forrest said. By comparison, conventional silicon chip-based solar cells are about 24 percent efficient. "Organic solar cells will be cheaper to make, so in the end the cost of a watt of electricity will be lower than that of conventional materials," said Peumans.
The technique the researchers discovered also opens new areas of materials science that could be applied to other types of technology, the researchers said. Solar cells are made of two types of materials sandwiched together, one that gives up electrons and another that attracts them, allowing a flow of electricity. The Princeton researchers figured out how to make those two materials mesh together like interlocking fingers so there is more opportunity for the electrons to transfer. The key to this advance was to apply a metal cap to the film of material as it is being made. The cap allowed the surface of the material to stay smooth and uniform while the internal microstructure changed and meshed together, which was an unexpected result, said Forrest. The researchers then developed a mathematical model to explain the behavior, which will likely prove useful in creating other micromaterials, Forrest said." 3:07:32 PM