Normally-closed shape memory microvalve

A new type of normally-closed gas microvalve is presented. The valve makes use of two micromachined SMA thin sheet devices, an active SMA device displaying the one-way shape memory effect and a passive superelastic SMA device, which maintains a normally-closed position. The outer diameter and height of the valve, are 6 mm. Gas flow experiments in stationary equilibrium reveal a maximum flow of 470 standard ccm (sccm) at a pressure difference of 8000 hPa and a power consumption of 260 mW. The dynamics of heat transfer to and from the active microdevice is investigated by infrared microscopy and coupled FEM simulations. At 300 mW heating power, the heating time is about 1.2 s. Typical cooling times vary between 1.8 and 5 s depending on the gas flow.