MEMS
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MEMS |
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Micro-Electro-Mechanical Systems: miniature power generators and microrockets etched from silicon. Real nanorobots will follow!
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Elsewhere on the Web
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• World's smallest rotary internal combustion engine
• Wired: Small Is Getting Bigger Every Day
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The late physicist Richard Feynman laid out the possibility of constructing objects atom-by-atom in his talk entitled There's Plenty of Room at the Bottom (1959). Eric Drexler, Ralph Merkle and other prominent researchers in this field also feel that there are no known physical limits - apart from technological ones - that should prohibit the construction of nanoscale devices. As we saw in one of the earlier articles on microscopic robots, today we lack most of the tools necessary for realizing the dreams of nanorobots, but things could change very soon. Several teams at University of California, Berkeley, are turning these dreams to reality, building true Micro-Electro-Mechanical Systems (MEMS).
Let's first take a look at the machine not much bigger than a stack of pennies that could potentially replace batteries as an efficient power source for mobile devices and robots. Carlos Fernandez-Pello, a mechanical engineering professor at UC Berkeley, led a team that developed the world's smallest rotary internal combustion engine (also known as a Wankel engine, this type of engine is sometimes used in concept and sport cars). The current prototype can produce up to 2.5 watts of electricity and runs on a fluid ounce of butane or propane for two hours. This engine, with a swept displacement of 77.5 cubic milimeters is constructed of hardened steel and aluminum. The ultimate goal of the project is to fabricate a "micro-rotary" engine etched from silicon and silicon-carbide, with a displacement of only 13 cubic milimeters that will be able to run 10 times longer than a conventional lithium ion battery.
Another team at the same university is testing solid-propellant microrockets, only 2 milimeters wide and 9 milimeters high. It is produced by etching a silicon wafer, much the same procedure used in microelectronics industry. The goal for its small but mighty engine is to propel a rocket with a 1 mg payload for several seconds. Each of its sensors would be no bigger than a grain of sand. The microrockets consist of a combustion chamber, a nozzle, an igniter, and solid propellant - hydroxyl-terminated polybutadiene (HTPB) fuel and ammonium perchlorate (AP) oxidizer. It is ignited with a hot wire and can blast up to 50 meters into the air. Hundreds of such inexpensive and disposable rockets could be used in military applications and weather exploration.
The ultimate objective of another similar project is to develop and demonstrate a silicon micro-machined, liquid-fueled, turbopump-driven, bipropellant rocket engine that is fully regeneratively cooled. The MIT/NASA Microrocket incorporates a liquid oxygen/ethanol rocket engine with a wafer-like structure - approximately 1.5 cm long, 1.2 cm wide, and about 2.5 mm thick, producing a thrust of a little over three pounds and an excellent thrust to weight ratio exceeding 10000 (compared to Space Shuttle's 70).
The application of microelectronic technology to the fabrication of mechanical devices has revolutionized the research in microsensors and microactuators. The White House has recently launched a National Nanotechnology Initiative (NNI) with a FY2000 budget of $270 million; in FY2001, the budget is scheduled to increase by 83% to $495 million. Electronic Components site at About.com offers a sampling of companies offering commercial MEMS-based products.