Papers by Author: Fadila Khelfaoui

Abstract: 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.

Abstract: Shape memory alloy (SMA) films enable the development of novel mechanically active microsystems as they provide large force and stroke in restricted space. The performance of SMA film actuators and sensors does not only depend on SMA material properties, but also requires a mechanically and thermally optimized design as well as a suitable fabrication technology being compatible to existing microsystems technologies. The paper gives an overview on the engineering aspects of SMA film actuators and sensors. These aspects are illustrated by selected examples such as bridge microactuators, microvalves and microscanners. The examples demonstrate the ongoing progress in the field, current limitations as well as existing opportunities for emerging new applications.