Understanding Smart Sensors - Nomads.usp

204 Understanding Smart SensorsTable 9.2Summary of Actuator Driver Requirements (After: [2])ConceptActuationStrengthActuationTimeInput PowerRequirementsThermopneumatic 34 kPa 0.03 sec 2.5WThermoresponsive polymer 437 kPa 0.05 sec 30 mWPhase change 100 kPa 0.04 sec 1.9 mWThermal blocking 100 kPa 0.015 sec 3WSMA 150 kPa 0.2 sec 0.12ABimetallic strip 50 kPa 1.0 sec 0.5ADielectric heating 4 Pa 0.02 sec 10V @ 4 MHzCapacitive 50 kPa md* 2700VPiezoelectric 25 kPa md 1000VElectrohydrodynamic 2.5 kPa 0.0004 sec 700VInterfacial tension 10 kPa 0.002 sec 1VMagnetorestrictive 50 kPa md 72ATwo coils 50 kPa md 18AFerromagnetic film 50 kPa md 1.4APermanent magnet 300 kPa md 0.3A*md = membrane dominatedelectromagnetic motors. An example of an electrostatic motor is shown inFigure 9.2 [4]. The rotor’s diameter is typically about 0.1 mm. The stator isactivated by pulses that produce an electrostatic force. Coupling the motor to aload and friction are among the problems that must be solved to make themotor useful. However, a fan for cooling ultrahigh-performance microprocessorsis among the possibilities that can be envisioned for this technology. Tribologyis the study of wear and is among the areas receiving considerableinvestigation for these machines, which cannot be lubricated using conventionalapproaches and which maintain the unique capabilities that MEMStechnology promises.The coil windings in a magnetic micromotor require a thicker actuatorcross-section. One approach uses a polyimide-based process that allows microstructuresto be fabricated on top of a standard CMOS process [5]. The core ofthe motor is multilevel electroplated nickel-iron wrapped around a meander