A new shape memory alloy microvalve based on surface acoustic wave

A new shape memory alloy (SMA) microvalve, which is switched on or off by surface acoustic wave, is presented. Two interdigital transducers with 27.5 MHz center frequency respectively are fabricated on a 128 degrees yx-LiNbO3 piezoelectric substrate for exciting surface acoustic waves. The surface acoustic waves are used for heating a paraffin oil droplet to raise the temperature of the SMA wire due to heating conduction. The spread distance of the two end of the SMA wire is then increased, which squeezed the polydimethylsiloxane (PDMS) microchannel connected with one end of the SMA wire by fixing the other end of the SMA wire in a printed circuit board. The microvalve is then switched off. Only removing the electrical signal off, the SMA wire is recovered softness state, and the fluid in the microchannel can then be transported driven by a syringe. The microvalve is switched on again. Red liquid is used to demonstrate the switching operation of the microvalve. Results show that the switching time of the microvalve is less 46s. The work is helpful for piezoelectric microfluidic devices for biochemical analysis.