DEVELOPMENT OF MICROACTUATORS BASED ON THE SHAPE-MEMORY EFFECT

The mechanical and electrical properties of beam-cantilever microdevic es fabricated from cold-rolled NiTi sheets and sputter-deposited NiTi thin films have been investigated by beam-bending experiments and elec trical resistance measurements, respectively. In order to study possib le size effects on the martensitic transformation, different device th icknesses have been realized down to grain dimensions of the NiTi shee ts of about 20 mu m, revealing enhanced transformation hystereses. For actuation control by resistive heating, the achievable displacements and work outputs were determined by the cross-section-dependent hear t ransfer to the device regions of maximum strain. Optimum heating/cooli ng performance and hysteresis control have been achieved for NiTi thin film devices with R-phase transformation above room-temperature. In o rder to demonstrate the potential of the microdevices for actuator app lications, prototypes of membrane microvalves have been realised and t ested.