Microelectromechanical systems (MEMS) refer to systems with characteristic length ranging between 1 µm and 1 mm, fabricated by integrated circuits batch processing technologies and unite mechanical and electrical components. MEMS devices and systems have wide applications in multifarious medical and industrial applications with worldwide market of billions of dollars. Examples of MEMS devices are accelerometers for automobile airbags; micropumps for inkjet printing, electronic cooling, and environmental testing; infrared detectors, digital light processing chip for projection display, etc. Microfluidics refers to fluid flow at a small size scale that causes change in fluid behavior. Microfluidic devices/systems handle a small quantity (micro- or nanoliter) of fluids (liquid or gas). The major application for handling fluids in microfluidics relates to chemical and biomedical analyses. The benefit of application of microfluidics in chemical and biomedical analysis is that they provide a total solution from sample utilization to display of analytical results.
TopMicroelectromechanical Systems (Mems)
MEMS technology is employed to fabricate miniaturized systems or devices integrating electrical and mechanical components. These systems are created in batches using techniques borrowed from integrated circuit (IC) processing technology. These devices/systems are capable to sense, actuate and control at micro scale and consequently realize result at micro scale.
MEMS is an interdisciplinary field so design and manufacturing requires expertise from broad and multifaceted technical areas comprising electrical engineering, material science, chemical energy, electrical energy, mechanical engineering, optics, integrated circuit fabrication technology, fluid engineering and instrumentation & control. MEMS devices and systems covers substantial market range which is the indicator of perplexity of MEMS. These devices find applications in the field of communication, medical, defense, electronics, automobiles, semiconductor, aerospace, optics etc.
MEMS is the most propitious technology for the current century which has possibilities to transform consumer and industrial product by amalgamation of semiconductor-based microelectronics and microfabrication technology. MEMS devices and systems has capability to affect mode of living and daily life. Semiconductor microfabrication and MEMS are observed as first and second micromanufacturing revolution respectively.
The word MEMS was originated in the United States of America. The same system technology is also referred as Microsystem Technology and Micromachines in Europe and Japan respectively. In a MEMS chip, electronic components are fabricated using IC technology, micromechanical components fabrication requires forming of structures on substrate using micromachining technology. Selective removal of material or addition of structural layers on substrates to create mechanical or electromechanical components requires high aspect ratio micromachining and bulk & surface micromachining. Many MEMS devices are fabricated using silicon as substrate material due to its unique electrical and mechanical properties.
The general form of MEMS device is shown in Figure 1. The device may consist of microelectronic systems, microstructures, microactuators and microsensors. All these subsystems are integrated on the same silicon chip. The role of microsensor is to sense any appreciable change in the system’s surrounding by estimating change in mechanical, electromagnetic, magnetic, chemical or thermal equilibrium and generate signal. These signals are processed by microelectronics and based on processing further input signal is generated for microactuators to create a suitable change in device hardware to accomplish the intended function. Microstructure forms the basis to form other miniature components. MEMS devices are miniature in size with microscopic components. MEMS technology was used to fabricate steam engines, motors, levers, pistons, gears etc., all at microscopic level. MEMS covers a wide engineering range. It means not all devices and systems are mechanical and made from silicon, but other systems and devices are fabricated without mechanical component and other diverse range of materials. MEMS represents devices and systems at microscale with complex subsystems having integrated microelectronics fabricated using batch fabrication techniques. Global MEMS market will cross USD 22.9 billion by the year 2027 as estimated by Markets and Markets (Markets and Markets, 2023).
Figure 1. Schematic of MEMS and its subsystems
Manufacturing techniques employed for MEMS fabrication include Electric Discharge Machining (EDM), Electrodeposition, Surface Silicon Micromachining, Lithography, Bulk Silicon Micromachining and LIGA (abbreviation for German word Lithographie Galvanoformung Abformung). Sensors and Actuators (collectively known as transducers) forms large portion of MEMS systems. The significant advantages of MEMS technology as compared to macroscopic electromechanical sensors are low noise & cost and high sensitivity. Low cost of such systems results due to parallel batch fabrication and obviation of manual assembly steps.