Vibroacoustic effects in MEMS

MEMS technology combines micromachining with microelectronics – the next logical step in the silicon revolution – and is very promising for aerospace, automotive, biological/ medical, military, and photonics applications. The term MEMS came into existence in the late 1980s although ‘bulk’ and ‘surface’ micromachining were developed earlier. A typical MEMS design incorporates at least one of the following components: a microsensor (accelerometer, load cell, microphone, etc.), microactuator (lever, gear, micro-mirror, valve, pump, motor, etc.), processor chip, and package. The size of microtransducers (microsensors and microactuators) is commonly measured in millimeters or even microns. While small size may be very important, for many mechanical systems miniaturization is not practical and the primary reason for MEMS is their low cost per device. The package shields the device from unfavorable thermal, vibration, acoustics, stress/strain, and electromagnetic effects, and connects it to the outside electrical circuits and mechanical mountings. During the last decade, silicon microtechnology produced a variety of sensors for measuring position, velocity, acceleration, pressure, sound pressure, force, torque, angle rate, flow, magnetic field, temperature, gas composition, humidity, pH, gas/liquid molecular concentrations, etc. To some extent, the contemporary MEMS products may be compared with Thomas Edison’s incandescent bulb that glowed dim and yellowish because the carbon-type filament turned to ashes with temperature. Only upon the implementation of tungsten filaments many years later did electric light bulbs become really luminous and robust. Currently, many of the MEMS designs described in publications are prototypes rather than robust industrial products. The reason is not just a deficit of optimal materials (like tungsten for Edison’s bulbs). Laboratory techniques, poor manufacturing bases, and organizational and financial pitfalls have been factors. It is likely that a lack of sufficient practical experience and theoretical knowledge has also contributed.