High frequency microfluidic performance of LiNbO3 and ZnO surface acoustic wave devices

Rayleigh surface acoustic wave (SAW) devices based on 128 degrees YX LiNbO3 and ZnO/Si substrates with different resonant frequencies from similar to 62 MHz to similar to 275 MHz were fabricated and characterized. Effects of SAW frequency and power on microfluidic performance (including streaming, pumping, and jetting) were investigated. SAW excitation frequency influenced the SAW attenuation length and hence the acoustic energy absorbed by the liquid. At higher frequencies (e. g., above 100 MHz), the SAW dissipated into liquid decays more rapidly with much shorter decay lengths. Increasing the radio frequency (RF) frequencies of the devices resulted in an increased power threshold for streaming, pumping, and especially jetting, which is attributed to an increased absorption rate of acoustic wave energy. ZnO SAW devices could achieve similar streaming, pumping, and jetting effects as well as frequency effect, although the SAW signals are relatively weaker. (C) 2014 AIP Publishing LLC.