Thursday, 21 February 2019

Microelectromechanical Systems

Microelectromechanical Systems


Micro electromechanical system (MEMS) is basically a technology used to create tiny integrated devices that combine mechanical and electrical components. They are fabricated using batch processing techniques with size varying from a few micrometres to millimetres. The acronym of micro electromechanical system has originated in the United States, though in Europe, it is recognized as micro system technology (MST), and in Japan, it is accepted as micro machining technology.

These devices or system have the ability to sense, control and actuate on the micrometre scale and produce effects on the macroscale. MEMS is interdisciplinary in nature, which has a wide and diverse range of technical areas including integrated circuit fabrication technology, mechanical engineering, materials science, electrical engineering, chemistry and
chemical engineering, as well as fluid engineering, optics, instrumentation and packaging. MEMS can also be found in systems ranging across automotive, medical, electronic, communication and defence applications.

Moreover, the key aspect of MEMS device fabrication is that, in the technique, it is fabricated. The micromechanical components are fabricated by classy manipulations of silicon and other substrates using micromachining processes. Processes such as bulk and surface micromachining as well as high-aspect-ratio micromachining (HARM) selectively remove parts of the silicon or add structural layers to form the mechanical and electromechanical components. Integrated circuits are designed only to exploit the electrical
properties of silicon; on the contrary, MEMS takes the advantage of other material properties like optical and mechanical. That is why these devices (or systems) have the ability to sense, control and actuate on the micrometre scale and generate effects on the macroscale.

History of MEMS (Microelecromechanical Systems)

1961: First silicon pressure sensor demonstrated. then
1967: Invention of surface micromachining. Westinghouse creates the resonant gate field effect transistor. Concept of surface micromachining with sacrificial layer first introduced.
1970: First silicon accelerometer demonstrated. Then
1979: First micromachined inkjet nozzle.
early 1980s: First experiments in surface-micromachined silicon.
1982: Disposable blood pressure transducer.
1982: ‘Silicon as a Mechanical Material’. Instrumental paper published to attract the scientific community – experimental data for etching of silicon first cited.
1982: LIGA (Lithography, Galvanoformung, Abformung) process demonstrated.
Late 1980s Micromachining facilitates microelectronics industry, and extensive experimentation and documentation increases public interest.
1988: First MEMS conference organized. Novel methods of micromachining modernized with an aim of improving sensors.
1992: MCNC (Microelectronics Center of North Carolina) starts the Multi User MEMS Process (MUMPS).
1992: First micromachined hinge and beginning of the Bosch Deep Reactive Ion Etching (DRIE) process.
1993: First surface micromachined accelerometer sold (Analog Devices, ADXL50).
1994: DRIE is patented.
1995: BioMEMS rapidly develops. Massive industrialization and commercialization.
2001: Triaxis accelerometers appear on the market.
2002: First nanoimprinting tools announced.
2003: For the purpose of volume applications, MEMS microphones introduced. Discera commences sampling of MEMS oscillators.
2004: Texas Instrument’s digital light processing chip sales rose to nearly
$900 million.
2005: Analog Devices embarked its 200 millions of MEMS-based inertial sensors.
2006: Packaged Triaxis accelerometers smaller than 10 mm3 are becoming accessible. Dual axis MEMS gyros appear on the market.
2006: Perpetuum launched vibration energy harvester.

Applications or Significance of MEMS

MEMS has several distinct advantages as a manufacturing technology. In the first place, the interdisciplinary nature of MEMS technology and its micromachining techniques, as well as its diversity of applications, have resulted in an unprecedented range of devices and synergies across previously unrelated fields (e.g. biology and microelectronics). Second, MEMS with its batch fabrication techniques enables components and devices to be manufactured with increased performance and reliability, combined with the obvious advantages of reduced physical size, volume, weight and cost. Third, MEMS provides the basis for the manufacture of products that cannot be made by other methods. These factors make MEMS potentially a far more pervasive technology than integrated circuit microchips.
MEMS technology finds applications in the following general fields :

MEMS techology use in Automotive Fields :

1. Air bag sensor
2. Vehicle security systems
3. Brake lights
4. Headlight levelling
5. Rollover detection
6. Automatic door locks
7. Active suspension

MEMS techology use in Consumer fields :

1. Appliances
2. Sports training devices
3. Computer peripherals
4. Car and personal navigation devices
5. Active subwoofers

MEMS techology use in Industrial fields :

1. Earthquake detection and gas shutoff
2. Machine health
3. Shock and tilt sensing
4. Toxic gas sensing
5. Optical device fabrication

MEMS techology use in Biotechnology field :

1. Polymerase chain reaction microsystems for DNA amplification and identification
2. Micromachined scanning tunnelling microscopes
3. Biochips for the detection of hazardous chemical and biological agents
4. Microsystems for high-throughput drug screening and selection
5. BioMEMS in medical and health-related technologies from lab-on chip to biosensor and chemosensor.

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