J. Phys. IV France 07 (1997) C5-597-C5-602
Stress-Optimised Shape Memory Devices for the Use in MicrovalvesK.D. Skrobanek1, M. Kohl1 and S. Miyazaki2
1 Forschungszentrum Karlsruhe GmbH, IMT, Postfach 3640, 76021 Karlsruhe, Germany
2 University of Tsukuba, Institute of Materials Science, Tsukuba, Ibaraki 305, Japan
A gas valve of 6x6x2 mm3 size has been developed for high pressure applications. Stress-optimised shape memory microbeams of 100 µm thickness are used to control the deflection of a membrane above a valve chamber. The shape memory thin sheets have been fabricated by melting and rolling, which creates specific textures. Investigations by X-ray diffraction revealed major orientations of  and  in rolling direction. The corresponding maximum anisotropy of transformation strain was 20%. The microbeams have been fabricated by laser cutting. For stress-optimisation, the lateral widths of the beams are designed for homogeneous stress distributions along the beam surfaces allowing an optimised use of the shape memory effect and a minimisation of fatigue effects. For actuation, a rhombohedral phase transformation is used. This allows operation below pressure differences of 1200 hPa in designs with one valve chamber and below 4500 hPa in pressure-compensated designs with a second valve chamber above the membrane. Maximum gas flows of 1600 sccm (sccm = cm2 at standart conditions / minute) and work outputs of 35 µNm are achieved for a driving power of 210 mW. The response times for closing the valves vary between 0.5 and 1.2 s and for opening between 1 and 2 s depending on the applied pressure difference.
© EDP Sciences 1997