Scanning electron microscope image of a spider mite on a polysilicon MEMS gear-train.        MEMS, or Microelectromechanical systems, (also written as micro-electro-mechanical, MicroElectroMechanical or "microelectronic and microelectromechanical systems") are also referred to as micromachines in Japan, or Micro Systems Technology (MST) in Europe. MEMS is the technology of the very small, and merges at the nano-scale into Nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are separate and distinct from the hypothetical vision of molecular nanotechnology or molecular electronics. MEMS are made up of components between 1 to 100 micrometres in size (0.001 to 0.1 mm) and MEMS devices generally range in size from 20 microns (20 millionths of a metre) to a millimetre. They usually consist of a central data processing unit, (microprocessor) and several components that interact with the outside world such as microsensors. At these size scales, the standard constructs of classical physics do not always apply. Because of the large surface area to volume ratio of MEMS, (which increases as component size decreases) surface effects such as electrostatics and wetting are more pronounced than volume effects such as thermal mass or inertia.        

        The potential of very small machines was appreciated long before the technology that could make them existed. Richard Feynman's famous lecture There's Plenty of Room at the Bottom, for example, introduced many of these concepts in 1959. MEMS became practical once they could be fabricated using modified semiconductor device fabrication technologies, normally used to make electronics. These processes include molding and plating, wet etching (KOH, TMAH) and dry etching (RIE and DRIE), electro discharge machining (EDM), and other technologies capable of manufacturing very small devices.

        The term NEMS, or Nanoelectromechanical systems, is used to describe devices integrating mechanical and electrical functionality on the nanoscale. NEMS form the logical next step of miniaturization from MEMS devices. NEMS typically integrate transistor-like nanoelectronics with mechanical actuators, pumps, or motors, and may thereby form chemical, biological, and physical sensors. The name derives from typical device dimensions in the nanometer range, leading to low mass, high mechanical resonance frequencies, potentially large quantum mechanical effects such as zero point motion, and a high surface to volume ratio useful for surface-based sensing mechanisms. Uses include accelerometers, or chemical detectors of substances in the air.



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