Chain gang


By Peter Hadfield in Tokyo A TENACIOUS micromachine that can hunt for flaws in pipes in confined spaces has been developed by a consortium of three of Japan’s largest industrial companies. Measuring less than a centimetre in length, the “experimental chain-type micromachine” (ECTM)—so named because several can be chained together—incorporates miniature gearing and one of the world’s smallest electric motors. The device was developed with government funding by Sumitomo Electric, Matsushita and Mitsubishi Electric, under the auspices of the Micromachine Center in Tokyo. It is designed to inspect the exterior surfaces of inaccessible pipes in power stations for cracks and flaws. “At the moment, pipework in power plants has to be disassembled in order to be inspected,” says engineer Kazuhiro Tsuruta of the Micromachine Center. “That’s time-consuming and very expensive. This type of micromachine will be able to check the pipes without having to take anything apart.” The box-shaped ECTM measures 9 by 6 by 5 millimetres and has been a decade in development. Using magnetised wheels to stick to a metal pipe, it can move at 7.2 metres per hour, propelled by an onboard electric motor just 1.6 millimetres in diameter. Power is supplied by very long, thin wires from a remote electrical source. The device can pass an electric current through the pipe over which it is travelling, detecting tiny cracks by noting increased resistance between two electrodes. The ECTM also incorporates a “microconnector”, a coupling that allows several micromachines to be chained together into a miniature train—a concept also being applied at a much smaller scale by molecular nanotechnologists (“The engine of creation”, New Scientist, 19 June 1999, p 38). Just 2.5 millimetres in diameter, the connector has spring-loaded plugs just 7 micrometres across on one side, and 200 micron wide sockets on the other side. Coupling and uncoupling is aided by electromagnets. “This connector is experimental,” says Kimihide Nakatsu, manager of the Micromachine Center’s research department. “At the moment there is no standard for these kinds of connectors. In the future, of course, we hope that this prototype will become the standard.” Even with a prototype, the ECTM is not ready for commercial exploitation. First, Tsuruta says he and other researchers will have to develop an onboard power source, since the wires supplying the ECTM limit its range. There is scope for battery power—the ECTM weighs 0.4 grams but has the capacity to carry loads up to twice its own weight. Japanese companies are trying to gain a lead in micromachine technology, which they believe will be a crucial market in the next century. “There are so many applications for micromachine technology,” says Mitsubishi’s Hide Yamada. “They’ll be able to work wherever humans can’t go—in tiny spaces, in very hot environments, and even environments where there is no air,
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