Localized particle patterning via standing surface acoustic wave micromanipulation

The current method of micromanipulation using standing surface acoustic waves generates standing wave patterns across the full width of the microfluidic channel and lacks the ability to perform localized manipulations. This paper analyzes and quantifies techniques for generating and controlling localized particle patterns in acoustic micromanipulation structures using surface acoustic waves of short-pulse excitation. An analytical computational model is developed to study waveform propagation under short-pulse excitation, considering the contribution of each finger pair in the forked-finger transducer. Additionally, a full-section simulation model of the vertical surface acoustic wave micromanipulator is combined with the finite element method to study the time-averaged base displacement of the micromanipulator and changes in the acoustic field distribution when pulse delay and frequency modulation are applied to the excitation signal. To validate the theoretical model, the micromanipulator device is fabricated and experimentally tested. The results demonstrate that modifying the relative time delay and an effective pulse time of the excitation signal enables effective control of the position and width of the generated standing wave region in the acoustic field, with a positive linear correlation between the two parameters and consistency with both theoretical and simulation results.