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.