J. Phys. IV France 115 (2004) 333
SMA microactuators for microvalve applicationsM. Kohl1, Y. Liu1, B. Krevet1, S. Dürr1 and M. Ohtsuka2
1 Forschungszentrum Karlsruhe, IMT, Postfach 3640, 76021 Karlsruhe, Germany
2 Tohoku University, IMRAM, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
This paper presents a study of the mechanical and thermal properties of SMA microvalves, which are driven by a microactuator of a NiTi foil or a Ni 2MnGa thin film. By coupled finite element simulations, von Mises stress profiles and resulting actuation forces are determined, which are compared with experimental force-displacement characteristics. The relatively high phase transformation temperatures of the used Ni 2MnGa specimens M / A of 92 / 125 C, give rise to cooling times of about 25 ms compared to 90 ms for NiTi. Thus, Ni 2MnGa microvalves show a superior switching performance. However, due to brittleness and buckling instability, Ni 2MnGa microvalves only allow a maximum controllable pressure difference of 70 kPa, which is more than a factor of 7 smaller compared to NiTi microvalves.
© EDP Sciences 2004