MicroElectroMechanical Systems (MEMS)IntroductionMEMS is the field of fabricating small electro-mechanical devices and systems. These devices range in size from a few microns to a few millimeters. It is also known as Micromechanics or Nano Technology (Nano technology usually refers to devices ranging in size from a nanometer to a micron). This field encompasses almost all aspects of science and technology, however, only on a smaller scale. MEMSs are usually rugged, respond rapidly, use very little power, occupy a small volume, and are often less expensive than conventional macro parts. Things behave substantially differently in the micro domain, study of which has developed into an area known as "micromechanics" (or nanomechanics). Forces related to volume, like weight and inertia, tend to decrease significantly. Forces related to surface area, such as friction and electrostatics, tend to become large. And forces like surface tension that depends upon an edge become enormous. Nature has provided some creatures the ability to work in the micro domain. An ant carrying many times its weight or a water bug walking on the surface of a pond are just two manifestations of the different micro world. Length Scale EffectCompared to their macroscopic analogs, MEMSs are controlled by a different set of physical principles. As mentioned before, surface forces play more important role in MEMS than those related to volume. This shift, obviously, is due to the small length scale of these devices. The effects of scale on MEMS design can be subdivided into three categories: quasi-fundamental, mechanism-dependent, and extrinsic (or independent). FabricationMicromachining plays very important role in fabrication of a group of MEMSs. Other techniques that have been successfully utilized to fabricate MEMS include LIGA (in German, Lithography, Galvanoformung, Abformung), Silicon Micromachining (surface and bulk), Electro Discharge Machining (EDM), Fab processes, etc. Most micromachining route involves etching silicon wafers by either dry or wet methods. Also isotropic and anisotropic etching are used in bulk micromachining.
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