• MEMS is any system that performs electrical and mechanical functions with components in micrometers is a MEMS.

• Micro-electro-mechanical systems [MEMS] is the integration of mechanical elements, sensors, actuators and electronics on a common substrate, through the utilization of microfabrication technology.

MEMS devices:

1) Air bag:

• Depending on crash, severity the rate of which the air bags are deployed is decided by the air bag control unit.

• In the event of a crash the balance force micro - accelerometer sends a signal to the air bag control unit.

• This control unit triggers the inflation device which generates nitrogen gas by igniting a mixture of sodium azide [Na $N_3$] and potassium nitrate [ x $NO_3$]

• The time between crash detection and complete deployment of air bag is approximately 0.05 seconds. The airbag speed is about 200 mph.

2) DMD : Digital micromirror device

• In DMD light modulator, we take an optical analog input and convert it into a digital format.

• It uses optical sensors and optical equipment's.

• DMD chip has on its surface several hundred thousand microscopic mirrors arranged in a rectangular array which correspond to the pixels in the image to be displayed.

• The mirror can be individually rotated $±10^o - 12^o%$ to an ON or OFF state.

• In ON state light from the projector bulb is reflected into the lens making the pixel appear bright on the screen.

• In the OFF state the light is directed else where [usually onto a heat sink] making the pixel appear dark.