A silicon electrothermal rotational micro motor measuring one cubic millimeter

A micro machined single crystal silicon micro motor has been developed that uses electrothermal actuators and micro assembly. The entire motor system occupies one cubic millimeter and can be integrated into a variety of packages. Four electrothermal bent-beam actuators in the stator drive the 290 mu m diameter 50 mu m thick rotor through friction-based contact. Flexures between the actuators and contact points step the rotor less than one degree with each driving waveform cycle; the motor can achieve 7.3 rpm. Since the micro motor is assembled it resists rotation in a power-off state and drives with 0.14 mu N m of torque. Details on the design, assembly and operation of the device are included. Finite element analysis has been applied to model the electrothermal transient response and achieve an 81% improvement in efficiency with 24 V pulse driving signals. The 1.2 mm by 1.2 mm by 0.7 mm device has been shown to rotate a 100 mu m diameter tungsten probe within the confines of a SEM.