Understanding Smart Sensors - Nomads.usp

210 Understanding Smart SensorsFigure 9.7 Four gears forming a transmission for increasing the force from a microengine.(Courtesy of Sandia National Laboratories.)9.2.5 Microsteam EnginesThe world’s smallest steam engine was fabricated with surface micromachiningtechnology [11]. Figure 9.8 shows the SEM of the device. Water inside thecompression cylinders is heated by electric current, vaporizes, and then pushesthe piston out. Capillary forces retract the piston when the current is removed.9.2.6 Actuators in Other Semiconductor MaterialsActuators have been designed and fabricated using thin film and plated metals,dielectrics, and photoresists for sacrificial layers on GaAs and InP substrates.GaAs and InP materials are used to fabricate MMIC devices, which requiretuning that potentially can be performed by on-chip actuators and result inimproved performance and yield. Sliding interdigitated capacitive tuners,bending beams, and rotating switches have been fabricated in a MMICcompatibleprocess as a first step toward their ultimate use to control theMMIC [12].Epitaxial silicon carbide (3C-SiC) films and sputtered amorphous SiCfilms have been investigated for high-temperature MEMS devices [13].