ZnO-based Acoustofluidics: Droplet-based Particle Manipulation

Droplet microfluidics as a cost-effective and precise branch of microfluidics provides shorter time analyses than the continuous-flow branch. This feature, along with a smaller amount of sample has attracted a large number of researchers. Here, a droplet-based Acoustofluidics platform is developed to investigate the imposed travelling surface acoustic wave (TSAW) and standing surface acoustic wave (SSAW) influence on polystyrene (PS) microbeads that are dispersed in a deionized water droplet. Aluminum interdigital transducers (IDTs) are patterned through a lift-off process over the zinc oxide (ZnO) thin film; the ZnO thin film serves as the piezoelectric layer which is RF sputtered on silicon oxide- silicon substrate. By tracing the PS microparticles motion, the effect of interacting forces in both TSAW and SSAW regimes is investigated and the formation of acoustic streaming vortices is shown.