Manipulating acoustic streaming in a droplet using a single surface acoustic wave transducer

Abstract

Acoustic manipulation offers a number of advantages, including non-contact operation, good biocompatibility, the elimination of the need for chemical biomarkers, and straightforward integration. These attributes render it a promising candidate for applications in materials science, precision engineering, and biomedical fields. However, the majority of acoustic manipulation techniques are unable to achieve diverse particle manipulation using a single sensor. In this paper, a multifunction micrometer-scale particle manipulation device based on a single interdigital transducer is proposed to manipulate acoustic streaming in a droplet. The interdigital transducer is equipped with arc-width variable fingers and is capable of being excited at multiple frequencies, thereby enabling the formation of different acoustic streams within a droplet. A finite element model of the device is constructed for the purpose of analysing its pressure distribution and a prototype transducer is subsequently fabricated. Diversity manipulation experiments are conducted using polystyrene (PS) particles of varying radii in a water droplet. The experimental results demonstrate that by modifying the frequency of the excitation signals, it is possible to manipulate the rotation of disparate particles. The combination of Acoustic Radiation Force (ARF) and acoustic streaming enables the performance of multifunctional particle operations, including rotation, separation, and directional movement, using a single surface acoustic wave transducer. This study presents a method for controlling acoustic streaming in a droplet with a simple device, which may have potential applications in drug delivery, particle sorting, and cell assembly.