| Biasing the Thermo-Mechanical Recovery of NiTi Thin Films Through Ion Implantation: A Technique Used to Fabricate Novel Micro-Actuators | ||
| Prof. David S. Grummon1, Dr. Thomas B. LaGrange2 and Dr. Rolf Gotthardt3, 1Chemical Engineering and Materials Science, Michigan State University, 3525 Engineering Blg., East Lansing, MI 48824-1226, 2Chemistry and Materials Science, Materials Science and Technology Division, Lawrence Livermore National Laboratory, 7000 East Avenue, P.O. box 808, Mail Stop, L-353, Livermore, CA 94550, 3Department of Basic Sciences, Institute of Physics of Complex Matter, Swiss Institute of Technology (EPFL), EPFL-FSB-IPMC, Ph-Blg. Station 3, Lausanne, 1015, Switzerland
We have explored a planar processing technique using ion implantation to develop a novel shape memory alloy (SMA) thin film actuator. In this technique, 6 μm martensitic thin films are first pre-deformed to 4 % tensile strain, and then, they are ion irradiated to damage levels which create defects that inhibit the martensitic transformation in a 2 μm thick damage layer. This creates a differential strain between the layers during heating and retransformation to the austenitic phase, causing the film to bend, out of plane, away from the irradiated surface. On subsequent cooling, the beam-damaged layer can act as an elastic spring that stores some of the strain energy released during the reserve transformation, which is then available to re-deform the martensite and reset the actuation for the next cycle. The irradiation parameters were varied, and the irradiated microstructure and the films’ thermomechanical response with thermal cycling were observed. The results will be discussed in terms of the actuator design and the relationship between the film’s motion and its microstructure. | ||