Micro-Electro-Mechanical System, or MEMS, is a miniature device or machine that is made of both mechanical and electrical components, using techniques of microfabrication.
The term ‘MEMS’ is often used for describing both a category of micro mechatronic systems and the process technology employed to manufacture them. Some MEMS do not have mechanical components, but since they convert certain mechanical signals into electrical or optical ones, they are classified as MEMS.
In Europe, MEMS are more commonly known as microsystems technology, and in Japan, it is referred to as micromachines.
Size of MEMS
The physical dimension of MEMS devices can range from 20 micrometers to one millimeter. They are made of components between 1 and 100 micrometers in size.
While individual components can be smaller than the width of a human hair, multiple modules arranged in arrays can occupy an area of more than a 10-centimeter square.
MEMS devices usually contain central data processing units (such as microprocessors) and tiny instruments that interact with surroundings (such as microsensors).
Types of MEMS
There are two forms of MEMS switch technology: ohmic and capacitive.
1. Ohmic MEMS switches are developed using electrostatic cantilevers. Since cantilevers deform over time, these switches can fail from contact wear or metal fatigue.
2. Capacitive switches are controlled by a moving plate or sensing element that alters the capacitance. By exploiting their resonant characteristics, they can be configured to outperform ohmic devices in specific frequency ranges.
How Are They Constructed?
While the interest in producing MEMS grew in the 1980s, it took nearly two decades to establish the design and manufacturing infrastructure required for their commercial development. One of the first few such devices produced were inkjet printheads and airbag controllers.
Using this technology, researchers were able to build a projector with micromirrors (which utilizes MEMS) in the late 1990s. Over time, microsensors became more popular: they were gradually integrated into different types of sensors, including sensors for radiation, magnetic fields, temperature, and pressure.
Today, MEMS are used in almost all smart devices, and they have become much more efficient (in terms of performance and energy consumption) than their larger counterparts. They are composed of parts such as microprocessors, microactuators, microsensors, several data processing units.
The fabrication of MEMS involves the same techniques that are used to create integrated circuits and semiconductor devices. The basic techniques are
- Deposition: Thin layers (between 1 and 100 micrometers) of material are deposited on a special surface.
- Patterning: A pattern is transferred into a material using a process called lithography.
- Etching: The material is dissolved either in a chemical solution or using reactive ions to produce the required shapes.
- Die preparation: Once MEMS devices are prepared on a silicon wafer, individual dies are separated, and then wafer dicing is performed through a cooling liquid or a dry laser process.
Silicon is the most common material used to create MEMS. It is readily available, inexpensive, and has substantial advantages, especially in the field of microelectronics. For example, silicon suffers very little fatigue and almost no energy dissipation.
Some MEMS are made of metal through electroplating, evaporation, and sputtering processes. Metals that exhibit high degrees of reliability include gold, platinum, silver, tungsten, copper, titanium, and aluminum.
Polymers can also be used to manufacture MEMS devices, as they can be produced in large volumes, with various material characteristics.
How Are MEMS Different From NEMS?
NEMS (short for nano-electro-mechanical systems) are a class of devices featuring electrical and mechanical characteristics on the nanoscale. NEMS form the next logical miniaturization step from MEMS.
In simple terms, NEMS are similar to MEMS but smaller: they have critical structural elements at or below 100 nanometers (atomic or molecular scales).
While NEMS and MEMS are referred to as separate technologies, they are depended on one another. For instance, a scanning tunneling-tip microscope, which detects atoms, is a MEMS device.
In MEMS technology, forces produced by fluid dynamics and ambient electromagnetism play an important role. Whereas in NEMS technology, surface-based sensing mechanism and large quantum mechanical effects are also crucial.
Unlike MEMS, NEMS technology utilizes carbon-based materials, specifically diamond, carbon nanotubes, and graphene. Due to substantial advances in growth, manipulation, knowledge of electrical and mechanical properties of graphene, researchers are taking more interest in graphene for NEMS devices, such as pressure sensors, resonators, accelerometers, and more.
Examples and Applications
As MEMS become more efficient and less expensive to build, they are expected to play a crucial role in the IoT (internet of things) and home automation. The common commercial applications of MEMS are:
The accelerometer in a smartphone | YouTube
- Accelerometers in vehicles for various purposes, such as electronic stability control and airbag deployment
- Sensor-driven cooling and heating systems for building management systems
- The optical switch used for switching technology and alignment for data communications
- Disposable blood pressure sensors and vehicle pressure sensors made of silicon
- Electrostatic, electromagnetic, and piezoelectric micro harvesters (used for energy harvesting)
- Small microphones, barometers, and gyroscopes to support smartphone applications
- Micronozzles used in inkjet printers to control the flow of ink.
Many companies are working on MEMS projects. Smaller firms offer value in innovative solutions and handle the expense of customized fabrication with high sales margins. Larger firms mostly manufacture high volume inexpensive parts or packaged solutions for end markets, such as electronics, biomedical, and automobiles. Generally, both small and large companies invest in research and development to build new MEMS technology.
According to the Grand View Research Inc, the global MEMS market size is estimated to reach US$28.84 billion by 2024. In 2015, it stood at nearly US$12 billion. Considering the increasing popularity of connected lifestyles, consumer electronics is expected to be the dominant segment (with over 40% of the global revenue share).
Calibration and accuracy issues may slow down market growth. But intense competition will force industry players to keep the prices low in the coming years.