MEMS sensors on flexible substrates towards a smart skin

This paper reviews the most recent results on the fabrication and characterization of a variety of microelectromechanical (MEMS) based sensors fabricated on flexible polymer substrates without the loss of performance, towards the development of a smart skin. These sensors include amorphous silicon based temperature sensors; nichrome based piezoresistive, absolute pressure sensors, tactile sensors and force sensors; and capacitive accelerometers. The sensors are sandwiched between a polyimide substrate and superstrate, placing them at a low stress plane, thus packaged at device-level. The flexible sensor package is grown during the device fabrication process. This allows the sensors to be integrated directly with flexible circuit boards to maintain overall flexibility. Some notable features are the incorporation of a sealed vacuum cavity for the absolute pressure sensors and the formation of a hermetically sealed cavity to contain the accelerometers in a constant atmosphere.