Recent Progress in FSMA Microactuator Developments

The giant magneto-strain effect is particularly attractive for actuator applications in micro- and nanometer dimensions as it enables contact-less control of large deformations, which can hardly be achieved by other actuation principles in small space. Two different approaches are being pursued to develop ferromagnetic shape memory (FSMA) microactuators based on the magnetically induced reorientation of martensite variants: (1) the fabrication of free-standing epitaxial Ni-Mn-Ga thin film actuators in a bottom-up manner by magnetron sputtering, substrate release and integration technologies and (2) the top-down approach of thickness reduction of bulk Ni-Mn-Ga single crystals to foil specimens of decreasing thicknesses (200 – 40 μm) and subsequent integration. This review describes the fabrication technologies, procedures for thermo-mechanical training adapted to the quasi-two-dimensional geometries of film and foil specimens as well as the performance characteristics of state-of-the art actuators after processing and training.