In the last 10 years, with the development of consumer electronics, especially smart phones and wearable electronics, MEMS sensors have really become popular all over the world, a large number of applications have emerged, and MEMS sensors really “fly into the homes of ordinary people”.
The full name of MEMS is micro electro mechanical system, which is translated into micro electro mechanical system. MEMS was first widely used in automobile airbag, and then widely used in various fields of automobile in the form of MEMS sensors.
With the further development of MEMS technology and the characteristics of “light, thin, short and small” application terminals, the demand for small volume and high-performance MEMS products is increasing rapidly, and a large number of MEMS products have appeared in consumer electronics, medical and other fields. For example, recently popular painless capsules for gastroscope, 5g street lamps, bone sensing headphones, intelligent system between washing machine and clothes hanger in smart home, elevator maintenance, etc.
However, now we have accepted the availability of low-cost, high-performance micro electro mechanical system (MEMS) sensors, but this is not always the case. In addition, from the perspective of application range, MEMS is wide enough to be recognized globally, but it will not stop here.
For example, at present, research teams of foreign universities use MEMS technology as a unique basis for building devices that cannot be manufactured. The international Solution Accelerator (achip) on the chip is a worldwide project to develop an electron accelerator that can produce femtosecond to attosecond. The electron pulse of silicon-based electron accelerator has energy of up to 1 megaelectron volt (MeV) and is completed by silicon chip, but its current required structure is up to a mile.
Engineers from the accelerator physics team at Darmstadt University of technology described how they created tiny MEMS channels and new electron beam focusing methods to replace the traditional electromagnetic focusing methods, but this method is too weak.
The silicon double column structure uses laser based optical phase control to focus the acceleration and deceleration regions of electrons（ Source: Darmstadt University of Technology)
Another innovative MEMS project is aimed at the world of the Internet of things (IOT). A team at Northeastern University has developed a MEMS based switch that consumes zero power when in sleep standby mode, but “wakes up” when hitting infrared (IR) light. The team’s plasmon enhanced micromechanical photoelectric switch (PMP) achieves this goal by converting a very small amount of photon energy in the defined spectral band to activate the MEMS mechanism. After removing the active IR energy, the switch will close itself.
In the above figure, each cantilever of the PMP includes a head, a pair of thermal bimaterial legs for actuation, a pair of external identical bimaterial legs for temperature and stress compensation, and a pair of insulated chain legs (a) connecting the inside and outside. Conceptual diagram of incident beams incident on four PMPs, each of which is “tuned” to a different infrared radiation band (b). The pseudo color scanning electron microscope image of the “mechanism” of the actually manufactured PMP switch has a high magnification (c) of the plasmon absorber, the bowl contact tip and the end of the bimaterial leg with self-aligned Al and SiO2 layers（ Picture from Northeastern University / natural nanotechnology)
For MEMS, Vijay Ullal, President of Maxim, said earlier that MEMS is the next technological revolution:
“The most interesting thing about MEMS is that it has been part of the industrial revolution more than 200 years ago since it began to turn energy into power. The major changes that followed were computing technology and the invention of transistors. The third important machine revolution was related to sensors. MEMS is not only a new invention, but also the third major change of human society. Any semiconductor company must do MEMS now, otherwise it may be kicked out of the industry. “
From the past history, we have used quite complex production processes to produce a small number of MEMS products. However, this method has obviously changed. At present, the electronic industry has quite successfully reduced the cost, the production process is becoming more and more mature, and the yield problem of MEMS is also stepping into the track, which is almost close to the index of traditional semiconductor process.
In the future, the development of MEMS technology may have a revolutionary impact on science and technology and human life like microelectronics.
Before any technology is adopted, it will go through a learning curve process. In the past, MEMS sensors were purchased only according to the price. Now, it is gradually found that not all components are made the same, and the functions and precision of sensing components are very different. With the evolution of time, the maturity of the market and the richer product portfolio, this field will be divided into an ultra-low cost market and many other market segments.
In terms of sensors, the development direction of sensors is array, integration and intelligence. MEMS is involved in several major trends. Because the sensor is the tentacle of human exploration of nature, the neuron of various automation devices, and has a wide range of applications, MEMS sensors will be paid more and more attention all over the world in the future.
In biology, biological MEMS system has the characteristics of miniaturization, integration, intelligence and low cost. It has the characteristics of large amount of information acquisition, high analysis efficiency, less connection between the system and the outside, real-time communication and continuous detection. Internationally, the research of biological MEMS has become a hot spot, which will soon bring a major innovation to biological and chemical analysis systems.
In optics, with the rapid development of information technology and optical communication technology, another field of MEMS development is the development of new optical devices combined with optics, which is called micro optical electromechanical system (MOEMS). MOEMS has the characteristics of small volume, low cost, batch production, accurate drive and control. The successful applied scientific research mainly focuses on two aspects: one is the new display and projection equipment based on MOEMS, which mainly studies how to spatially modulate light through the physical movement of the reflecting surface, which is typically represented by digital micro mirror array chip and grating light valve; The second is the communication system, which mainly studies the expected change of the optical path through the physical movement of the micro mirror. The more successful optical communication devices include optical switch modulator, optical filter and multiplexer. MOEMS is a high-tech with strong comprehensiveness and interdisciplinary. Carrying out scientific and technological research in this field can drive the development of a large number of new concept functional devices.
In terms of nanotechnology, MEMS combined with nanotechnology will realize real micro sensors and develop new applications, although this progress may take a decade. In another 10 to 15 years, the self-assembled structures seen in the laboratory will use real micro sensors, which can operate almost completely without any power.