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Working Microdevices Edge Closer To Reality
SOPHIE WILKINSON
"Fantastic Voyage"--the film in which a miniaturized Raquel Welch and her colleagues venture through a patient's bloodstream in a tiny submarine--no longer seems so fantastical. Recent news reports have described a camera-containing pill that photographs the digestive tract. And Japanese researchers have now made microdevices that could proceed through the body "through even the smallest blood vessels, for example, to deliver clinical treatments" [Nature, 412, 697 (2001)].
Applied physics professor Satoshi Kawata and coworkers at Osaka University have crafted what they say are the smallest model animals and among the smallest functional micromechanical systems ever made. Their "micro-bulls" are 10 µm long and 7 µm high, about the size of a red blood cell. Their similarly sized "micro-oscillator system" consists of a bead fastened to a spring attached to a cubic anchor. The scientists employ laser-trapping force to catch hold of the bead and pull on it. When released, the bead moves as the spring contracts and relaxes.
The Japanese team uses "two-photon photopolymerization" to create the 3-D structures. An infrared laser is beamed into a liquid urethane-acrylate resin containing photoinitiators, and the resin solidifies wherever two photons are simultaneously absorbed. Movement of the laser's focal point location is managed by computer. After the pattern is completed, unreacted resin is washed away. The researchers bettered the technique's previous minimum feature size of 600 nm by controlling laser-pulse energy and exposure time to give a resolution of 120 nm.
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DOWNSIZED The fine features of the bull and the functionality of the ball-on-a-spring device demonstrate the laser technique's capabilities.
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Chemical & Engineering News
Copyright © 2001 American Chemical Society |
