MICROELECTROMECHANICAL SYSTEMS (MEMS)

Microelectromechanical systems (MEMS) have experienced a revolution in recent years. These systems integrate sensors with their readout electronics, signal processing and control circuits, microprocessor, and power supply in a single package. Silicon capacitive sensors are made of single crystal silicon and glass. This design ensures good linearity, accuracy, and stability over time and temperature. Hermetically sealed structures prevent particles or chemicals from entering the element, which increases reliability. In principle, MEMS sensors can be designed for measuring many different quantities such as temperature, pressure, acceleration, electric voltage, or current [1].

There are two different approaches for building MEMS devices, bulk micromachining and surface micromachining. The bulk micromachining process is normally used to make pressure sensors. Surface micromachining is normally used to make accelerometers [2]. However, Motorola is now using surface micromachining to make the pressure sensor in its new tire-pressure monitoring system.

The InTire sensor, which is part of the Michelin eTire System, uses a capacitive MEMS device to sense pressure and temperature.

References

[1] "Intelligent Tyre for Accident-free Traffic," APOLLO Final Report, IST-2001-34372, July 2005.

[2] Gary Legg, "MEMS Sensors Rev Their Engines," Design News, May 05, 2003, https://www.designnews.com.