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Technology Bulletin

Technology Bulletin

Biking with new composite offers less weight but more durability

Anyone that has ever mountain biked knows that the crankshaft, the metal part that connects the pedal to chain ring, takes a beating. It better be strong, lightweight, and reliable. But "aluminum cranks have reached their peak performance--they can't shed weight without suffering a loss of stiffness and performance," says Craig Pollack, president of Race Face Components Inc. (New Westminster, British Columbia, Canada). So company engineers turned to carbon fiber. But pure carbon fiber cranks can't take the punishment that serious mountain bikers deliver. To combine the best of both worlds, Race Face engineers designed a unique forged and CNC machined heat-treated aluminum exoskeleton for the crank. The open interior of the shell is filled with a carbon fiber resin material that is then hardened through a proprietary process to add its lightweight, high-strength properties to the aluminum. The exoskeleton protects the carbon fiber from chipping and provides the crank with the durability required by mountain bike racers. "Discovering how to combine the strengths of both materials is an outstanding achievement by our research and development department," says Pollack. "This advance is certain to have applications in other manufacturing industries."

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A two-layered heat sink keeps things cool

Heat is a problem that everyone. Knowing this, Kambiz Vafai, professor of mechanical engineering at Ohio State University (Columbus, OH), and graduate student Lu Zhu took a conventional heat sink design--the micro-channel heat sink--and made it cooler, figuratively and literally. A micro-channel absorbs heat by circulating coolants such as water through a network of tiny tubes. More is always better, right? So Vafai and Zhu doubled the number of tubes used in the design. "Micro-channels are useful for electronics because they provide a great deal of cooling, and multiplying the number of channels allows coolant to penetrate much more effectively into the system," said Vafai. However, this theory wasn't without its challenges. Traditionally, to help such small tubes remove a large amount of heat manufacturers must pump coolant through the sinks at high pressure. This requires a large power supply and bulky packaging. Vafai and Zhu found that if they layered an identical second bed of cooling channels on top of the first, they could dissipate more heat and eliminate the need for a larger power supply. In the two-layer heat sink design, coolant flows through micro-channels directly next to a heat source, into a heat exchanger, then through the second layer of micro-channels. In computer simulations, the temperature of a micro-electronic circuit using the new design rose only 9F compared to 27F for a circuit using a conventional heat sink. "By designing this two-layer structure, we haven't significantly complicated the manufacturing process, but we've substantially eliminated the problems associated with the one-layer micro-channels," said Vafai. He filed a patent application for the design, and several companies are inquiring about commercializing the technology. E-mail: [email protected]

New techniques for creating polymer thin materials

Polymer thin films are quite popular these days. They are found in time-released medications, LCDs, slow-release fertilizers, antireflective coatings, and more. As scientists work to create new polymer thin-films by using blends of polymers, however, they often find that many polymers simply don't mix. In an attempt to get around this, Harald Ade, associate professor of physics at NC State, doctoral student D.A. Winesett and colleagues from SUNY-Stony Brook showed, for the first time, that highly dissimilar polymers can be completely blended into a thin film by exploiting reduction in entropy--a measure of the number of possible molecular arrangements in a material--that occurs as a result of miniaturization. "It's sort of like getting water and oil to mix," Ade says. "The beauty of nature is that if a polymer blend is shrunk small enough, the emulsifier utilized is essentially prevented from associating with other emulsifier molecules due to the confined space." Emulsifiers are agents that mediate between different polymer types and act like a "detergent," stabilizing the polymer mixture. If, however, the emulsifier molecules associate with other emulsifiers, they lose much of their stabilizing ability and the polymers they once held together can separate, causing unacceptably large modulations on the surface of the material and inconsistent structure within it. Such flaws would render a material useless for most modern applications, where a perfectly flat surface is required and tight structural tolerances exist. In contrast, "the thin-film polymer blend we created was made from very dissimilar polymers, but it had a perfectly flat surface and a completely mixed, uniform structure when reduced to nanoscale," Ade says. "This is the first time we've seen that in highly immiscible systems." Because the new blending technique doesn't depend on chemistry, scientists should be able to use it on nearly any polymer blend. "This will have a significant impact on any technological process that relies on ultra-thin polymer coatings, such as photolithographic printing, and magnetic disk coating," says Winesett. E-mail: [email protected].

Writing nanostructures with the world's smallest plotter

The scientists who gave us the world's smallest pen now bring us the world's smallest printer. The printer draws multiple lines of molecules, each line only 15 nanometers or 30 molecules wide, with such precision that only five nanometers or about 200 billionths of an inch separate each. A research team led by Chad Mirkin, Charles E. and Emma H. Morrison Professor of Chemistry and director of Northwestern's Center for Nanotechnology (Evanston, IL) developed the device by expanding on their dip-pen nanolithography (DPN) technique. "Our dip-pen nanolithography allowed us to draw tiny lines with a single 'ink' or type of molecule," Mirkin says. "Now, with the nano-plotter, we can place multiple 'inks,' or different kinds of molecules, side by side with such accuracy that we can retain the chemical purity of each line. In a sense, we have transitioned from a single ink process to a four-color printing type of processon a nanometer scale." DPN, described in the Jan. 29, 1999, issue of Science, turns an atomic force microscope (AFM) into a writing instrument. Researchers first apply an oily "ink" of octadecanethiol (ODT) to the AFM's tip. When the tip is brought into contact with a thin sheet of gold "paper," the ODT molecules are transferred to the gold's surface via a tiny water droplet that forms naturally at the tip. The new nanoplotter multiplies this technique, laying down a series of molecular lines with extreme accuracy. While the microfabrication of electronic circuits and other products currently use solid-state or inorganic materials, innovations such as the nano-plotter will direct future technologies toward the use of organic and even biological materials. "This technology should become a real workhorse for the nanotechnologist," Mirkin said. "It will soon be possible to pattern one master plate with thousands of different organic nanostructures, each structure designed to react with a certain disease agent, for example. That's what is exciting about this--no other method exists to do this on such a small scale." E-mail: [email protected].

An 'up close' and personal look at Neptune

Neptune is a mostly gaseous planet, and only the upper layers of its atmosphere are visible. The planet is so distant that normally it is impossible to detect fine detail with terrestrial telescopes. But a new infrared camera and adaptive optics system cuts through atmospheric turbulence as if it weren't there and shows the planet embellished with a massive cloud, the size of the European continent, and numerous smaller clouds. The astronomers also took high-spatial-resolution spectra of the atmospheric features. "This is the only instrument currently available that provides both the high spatial resolution of an adaptive optics system and, at the same time, spectral information," says Cornell astronomer Don Banfield. The camera, the Palomar High Angular Resolution Observer (PHARO), developed by Cornell researchers for the California Institute of Technology's 200-inch Hale telescope at Palomar Observatory, receives light from a new adaptive optics system developed by a team from NASA's Jet Propulsion Laboratory (JPL) led by Richard Dekany. The adaptive optics system is basically a mirror placed between the telescope and camera. The mirror adjusts up to 500 times per second to correct atmospheric distortions. The researchers believe that these optics are competitive with any telescope in the world, and even the orbiting Hubble Space Telescope, for the clarity of images. E-mail: [email protected].

Underwater portable chemical sensor detects unexploded devices

Detecting unexploded mines and bombs continues to be a serious problem, under the water as well as on land. But a portable chemical sensor system from Sandia National Laboratories (Albuquerque, NM) may solve the water portion. The system samples the water surrounding submerged objects, extracts the molecules of interest on a fiber, desorbs the molecules from the fiber in an Ion Mobility Spectrometer (IMS) and identifies the explosive based on the material's chemical signature. At the heart of the device is a concentration technology that distills the sample to levels large enough to analyze. Ron Woodfin, project manager, and fellow researchers miniaturized the IMS, reducing it from a commercially produced 30-lb shoebox-size device to a five-lb unit that fits in a person's hand. When complete, the entire system including the IMS, concentrator, computer, display, and batteries, will be the size of a soccer ball and weigh no more than 20 lb. E-mail: [email protected].

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