Special Issue on MEMS for Robotics and Mechatronics
Authors: Esashi Masayoshi , Tanaka Shuji , Aoyagi Seiji , Mineta Takashi , Suzumori Koichi , Dohi Tetsuji , Miki Norihisa 
Published: April 2020

MEMS (Micro Electro Mechanical Systems) is a technology that is used to incorporate sensors, actuators, microstructures, and circuits on chips by using a combination of various technologies with semiconductor process. MEMS are also used in robotics and mechatronics since they can provide compact, low-cost functional components that play crucial roles in their respective systems. We would like to elaborate on the history of MEMS technology, whose initial development started around 1970.

In 1960s, Dr. Isemi Igarashi of Toyota Central R&D Labs., Inc. in Japan developed a semiconductor pressure sensor of piezo-resistance type. In 1980s, the pressure sensors were used to control automobile engines to clear exhaust gas regulations and thus contributed to solving environmental issues. In 1990s, semiconductor acceleration sensors were used for passive safety technologies to detect collision of automobiles and activate air bags, which resulted in decrease in traffic fatalities. In 2000s, an active safety system with gyro sensors was developed to detect and control spinning of a vehicle. In future, space recognition sensors with optical scanners to measure light propagation time and detect distance to an object will be used for autonomous driving.

For smartphones, a microphone, an acceleration sensor, and a gyro sensor are used in user interface, and a film bulk acoustic wave resonator (FBAR) is used in a wireless communication filter. For projectors, the built-in circuit of a mirror array system is used to move mirrors placed in an array. After the development of projectors, films have not been used in movie theaters.

MEMS are also widely used in medical and biological fields, such as blood pressure measurement. Esashi began research on a semiconductor ion sensor ISFET (ion sensitive field effect transistor) in 1971. ISFET detects ion concentration in electrolyte by exposing the insulating film of an insulated gate transistor to the liquid. He set up a prototyping facility when he was a graduate student and wrote only one paper on this research, although the prototyping facility was used afterwards. The ion sensor was certified under the Pharmaceutical Affairs Law after a 12-year application process and was used as catheter-type pH sensor to diagnose reflux esophagitis. MEMS are widely used for minimally invasive medical treatment, which causes minimum damage to human body. Moreover, MEMS are used as disposable sensors to prevent infection or as implanted devices.

In addition, MEMS are used for production inspection and scientific instrument, including scanning probe microscopes (SPMs), which observe atoms using extremely small nano-probes, and probe cards that simultaneously test several integrated circuits on a wafer using aligned probes.

When he was an associate professor, Esashi improved the prototyping facility that he made when he was a student and made a large scale integrated circuit (LSI). After he became a professor, he accepted researchers from more than 130 companies and developed MEMS using the prototyping facility to develop a product through the academia-industry collaboration. He realized integrated MEMS by combining LSI and MEMS. This includes a system of many tactile sensors attached on the body surface of a safe robot for real-time detection of contact through packet communication.

After he retired from the university, he developed a “prototype coin laundry,” which enables companies to do develop without having their own prototyping facility. The prototype coin laundry is a system where engineers can use the prototyping facility to develop devices, and the system has been managed by successors. Unlike integrated circuits for which standardization is easy, standardization of MEMS is challenging because of difficulty in development. It is necessary to access various knowledge for the development of MEMS, and he has made efforts to provide the knowledge.

Finally, we would like to thank authors who submitted papers to this Special Issue on MEMS for Robotics and Mechatronics as well as those who were involved in editing and reviewing the papers. We sincerely hope for further development in this field of research.