5 - MEMS devices

Thermal radiation sensors

Infrared detector array

In the MEMS cantilever based infrared detector each plate acts as the upper electrode of a variable capacitor. When the plate absorbs heat, the bimaterial arm bends, and moves the the plate up, proportional to the amount of absorbed heat energy. The reference electrode is implemented on the substrate. An array of these detector produces a high resolution heat-map image without cooling.

Thermal conductivity sensor

The thermal conductivity sensor operates by observing the changing resistance of sensor resistor in response to an input to the heater filament. When not in contact with an object, the only route for the heat input of the heater to reach the sensor resistor is through the substrate and the surrounding air. When an object comes in contact with the sensor, the low efficiency heat path through the air is replaced by solid conduction, changing the character of the signal measured at the sensor resistor, with a square wave voltage input to the heater. The time constant of the temperature of sensor resistors is found to be a function of contact object thermal conductivity.

When using magnetic data storage the information bits are stored in magnetic domains having different magnetization direction within the thin magnetic film. The remagnetization of domains (the writing process) and the recognition of the magnetic state (reading out data) are made by read/write heads. The working principle of magnetoresistive (MR) and giant magnetoresistive (GMR) is shown on the animation.
The free electron path is different when electron spins are parallel or antiparallel to the magnetic field.