Field nonuniformity of limited-aperture planar SAWs and its implications for designing SSAW acoustofluidics

Abstract

Acoustofluidics operating at high frequencies usually use surface acoustic waves (SAWs), and those emitted by limited-aperture planar interdigital transducers (IDTs) are prevalent. In such devices, field nonuniformity along the lateral direction is observed by many, but there lacks a study to quantitatively clarifying this effect. Here, by modeling IDTs using dirac-type transfer functions, we examine how field nonuniformity changes at varied aperture length, axial distance, and number of finger pairs of the IDTs. For standing SAW (SSAW) devices, field predictions from numerical analysis are validated through experimental measurements employing laser vibrometry. Finally, particle acoustophoresis is carried out in three SSAW devices, while the results provide some useful implications for future device designs.