A gas valve of 6x6x2 mm(3) size has been developed for high pressure a
pplications. Stress-optimised shape memory microbeams of 100 mu m thic
kness are used to control the deflection of a membrane above a valve c
hamber. The shape memory thin sheets have been fabricated by melting a
nd rolling, which creates specific textures. Investigations by X-ray d
iffraction revealed major orientations of [111] and [011] in rolling d
irection. The corresponding maximum anisotropy of transformation strai
n was 20%. The microbeams have been fabricated by laser cutting. For s
tress-optimisation, the lateral widths of the beams are designed for h
omogeneous stress distributions along the beam surfaces allowing an op
timised use of the shape memory effect and a minimisation of fatigue e
ffects. For actuation, a rhombohedral phase transformation is used. Th
is allows operation below pressure differences of 1200 hPa in designs
with one valve chamber and below 4500 hPa in pressure-compensated desi
gns with a second valve chamber above the membrane. Maximum gas flows
of 1600 seem (seem = cm(2) at standart conditions ! minute) and work o
utputs of 35 mu Nm are achieved for a driving power of 210 mW. The res
ponse 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
.