MEMS (micro-electromechanical systems)
A MEMS (micro-electromechanical system) is a miniature machine that has both mechanical and electronic components. The physical dimension of a MEMS can range from several millimeters to less than one micrometer, a dimension many times smaller than the width of a human hair.&
The label MEMS is used to describe both a category of micromechatronic devices and the processes used when manufacturing them. Some MEMS do not even have mechanical parts, yet they are classified as MEMS because they miniaturize structures used in conventional machinery, such as springs, channels, cavities, holes and membranes. Because some MEMS devices convert a measured mechanical signal into an electrical or optical signal, they may also be referred to as transducers. In Japan, MEMS are more commonly known as micromachines, and in European countries, MEMS are more commonly referred to as microsystems technology (MST).
How MEMS are constructed
MEMS are composed of parts such as microsensors, microprocessors, microactuators, units for data processing and parts that can interact with exterior pieces.
Unlike conventional mechatronic devices, MEMS are often manufactured with the same batch fabrication techniques used to create integrated circuits (ICs) and many commercial MEMS products are integrated and packaged together with ICs. MEMS fabrication allows micro-sensors, which gather data, and micro-actuators, which convert energy into motion, to integrate on the same substrate.
Although MEMS have a low per-device production cost, packaging can be a challenge. Each MEMS must be packaged so that electrical or optical circuitry and other device components remain free from air and water contamination, while still being able to interact with the surrounding environment and accommodate motion.
Examples of MEMS
The small system on a chip (SOC) that automatically adjusts screen orientation on a smartphone is an example of a MEMS many people interact with each day. As MEMS become smaller, require less power and are less expensive to manufacture, they are expected to play an important part in the wireless internet of things (IoT) and home automation<.
Other commercial applications of MEMS include:
- Sensor-driven heating and cooling systems for building management systems.
- Micro-mirror arrays for high definition projection systems.
- Smart dust for the detection of environmental changes in molecular manufacturing (nanotechnology) clean rooms.
- Micronozzles to control the flow of ink in inkjet printers.
- Tiny gyroscopes, barometers, accelerometers and microphones to support Mobile apps.
- Disposable pressure sensors for use in healthcare.
- Optical switching devices that allow one optical signal to control another optical signal.
The MEMS below is a disposable, wearable insulin pump for managing diabetes, designed by Debiotech and STMicroelectronics. According to Debiotech, the chip is a stack of 3 layers bonded together: a silicon on insulator (SOI) plate with micromachined pump structures and two silicon cover plates with through-holes. A piezoelectric actuator on the chip moves the membrane in a reciprocating movement to compress and decompress fluid in the pumping chamber.
History of MEMS
The idea of creating MEMS started in the 1980s; however, the means to produce MEMS (the designing and manufacturing infrastructure) was not available enough until the 1990s. One of the first few types of MEMS produced were for air-bag controllers and inkjet printheads. In the late 1990s, a projector was made using micromirrors (which utilizes MEMES). Much of the original support for MEMS came from the Defense Advanced Research Projects Agency Research and Development Electronics Technology Office.
Over time, microsensors began being used for a large number of sensor types, including sensors for temperature, pressure, magnetic fields and radiation. In many cases, sensors that used MEMS were much more efficient performance wise when compared to larger counterparts.
Today, most people interact with MEMS daily. Each new automobile that rolls off an assembly line has at least 50 MEMS; they are essential components in various mandated safety systems, including airbags, electronic stability control (ESC) and tire pressure monitoring systems (TPMS).
MEMS vs. NEMS
While MEMS stands for micro-electromechanical system, NEMS stands for nano-electromechanical system. NEMS would be used in Nanotechnology, which is a technology that can manipulate matter at a nanoscale (around the atomic or molecular level). A top-down approach to nanotechnology uses devices that share many similar techniques to MEMS. MEMS and NEMS are sometimes referred to as separate technologies but can be considered as dependent on one another as NEMS technologies are required for NEMS. As an example, a scanning tunneling-tip microscope (STM), which can detect atoms, is a MEMS device.
This video from the MEMS & Sensors Industry Group provides an introduction to MEMS technology.
