Highly Efficient Liquid Flow Actuator Operated by Surface Acoustic Waves

Abstract

Surface acoustic wave (SAW) devices, because of their very simple structures, can be used as component parts for micro total analysis systems. We focused on a liquid flow actuator operated by SAWs and investigated highly efficient interdigital transducers (IDTs) to generate SAWs. The IDTs were fabricated by patterning Al/Cr on a LiNbO3 substrate. In an IDT with a stripline pitch of 200μm, effective water droplet streaming was produced. We also fabricated a continuous liquid flow actuator consisting of both an IDT and a flow channel made of epoxy-based negative resist SU-8 on one chip. To diversify the liquids used, we created an actuator design in which the IDT and liquid do not directly touch one another at the partition wall. Using this chip, we succeeded in creating a continuous flow of liquid using the SAWs. When 160mW of electric power was applied, the liquid flow rate of the actuator was approximately 7.8μL/s. We experimentally found that the electric power applied to the IDT was proportional to flow velocity and that the IDT with 200μm pitch produced effective continuous liquid flow as well as water droplet streaming.