Micro-Electric-Mechanical System, or MEMS, is the technology of very small mechanical devices driven by electrical or mechanical system. MEMS are made up of components between 1 to 100 micrometers in size (0.001 to 0.1 mm). Micro-scale devices are fabricated using modified semiconductor device fabrication technologies, including molding and plating, wet etching (KOH, TMAH) and dry etching (RIE and DRIE), and surface micro-machining. Like integrated circuits, MEMS fabrication technology utilizes many materials like silicon, polymers, metals and ceramics. Processes include deposition of materials on silicon wafers, patterning with ultra-violet or X-ray photolithography, and etching in solution or plasma gas. MEMS technology has many applications in sensor, actuator and micro-structures: inkjet printer, accelerometers, gyroscope, pressure sensor, microphone, optical micro-mirror, fluid channel, etc.



 LIGA is the German acronym for X-ray lithography (X-ray LIthographie), electroplating (Galvanoformung), and molding (Abformtechnik). Since a synchrotron radiation source is used in the lithography, this process is generally used to fabricate high-aspect-ratio microstructures with a thickness in the range of dozens of micrometers to several centimeters. In addition, the structures have precise dimensions and good surface roughness. UV-LIGA use ultra-violet light instead of X-ray source. Photoresists like SU-8 is used for high aspect ratio of molds.

2. Piezo-MEMS

 Piezoelectric is that external forces applied to single crystals of quartz and several other minerals generate a charge on the surface of these crystals. The charge is roughly proportional to the applied mechanical stress. These so-called piezoelectric materials discovered in 1880-81 by Pierre Curie and his brother Paul-Jacques. A year later, the Curie brothers discovered the inverse effect which is that an applied voltage generates a deformation of the crystal. This property of materials can be utilized for electric-mechanical actuators and sensors.

3. Bio-MEMS

 Today, micro-chip devices are making major contributions to the drug discovery process. In this application, a capability for rapid high-throughput multiplexed analysis using low volumes of sample and reagent is paramount, and the microchip devices offer a convenient and cost-effective approach to this type of analytical process. As biotechnology merges with micromachining, there are three examples: miniaturized PCR, DNA chips, and immunosensors, or other example like as microphysiometers, blood gas and blood electrolyte sensors, Lab-on-a-chip, etc.