Highly efficient liquid flow actuator operated by surface acoustic waves

Abstract

SUMMARYSurface 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 LiNbO 3 substrate. In an IDT with a stripline pitch of 200 µm, 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 160 mW of electric power was applied, the liquid flow rate of the actuator was approximately 7.8 µL/s. We experimentally found that the electric power applied to the IDT was proportional to flow velocity and that the IDT with 200 µm pitch produced effective continuous liquid flow as well as water droplet streaming.

High‐Efficiency Mixing Chip with Liquid Flow Actuators Operated by Surface Acoustic Waves

“…When using this type of burst waveform, the duty ratio was approximately 10% and substrate damage due to heat was prevented. This sinusoidal frequency is also a frequency corresponding to the pitch (200 µm) of an IDT with a relatively high liquid transport efficiency for water obtained in our prior research . The impedances of the IDT at this frequency used in the present experiment were 8–10 j Ω , respectively.…”

“…Actuators and sensors that take advantage of sound waves (surface acoustic waves: SAW), which propagate with their energy concentrated only on the surface of an elastic body, have been described. If the propagation surface of a SAW is on the object, then the object moves and the SAW attenuates due to the interaction between them.…”

“…However, there is only one report on solution transport in a closed space using SAW, and there are no reports on transporting a solution through a continuous system on one chip. Thus, we previously proposed a pump operated by SAW with a customized configuration, and succeeded in transporting a solution in a continuous system with the pump installed on a chip .…”

“…However, these SAW‐operated mixers also use droplets, and the same problems as are found in SAW‐operated pumps remain. Thus, we fabricated a micro liquid rotor operated by SAW based on the SAW‐operated pump developed previously, with the idea of a highly efficient mixer in a channel or other closed space in mind .…”

“…In the present research, based on the SAW‐operated pump and the micro liquid rotor , we fabricated a new micro continuous liquid system mixing chip using as a drive source only a SAW, consisting of a pump, mixer, and flow channel. We evaluated the chip's mixing and chemical reaction characteristics.…”