Separation of 300-nm and 100-nm particles in Fabry-Perot acoustofluidic resonators

Separation of particles on the order of 100 nm with acoustophoresis has been challenging to date because of the competing natures of acoustic radiation force and acoustic streaming on the particles. In this work, we present a surface acoustic wave (SAW)-based device that integrates a Fabry-Perot type acoustic resonator into a microfluidic channel to separate submicron particles. This configuration enhances the overall acoustic radiation force on the particles and thereby offers controlled manipulation of particles as small as 300 nm. Additionally, SAW-based excitation generates high-frequency acoustic waves in the system relative to bulk acoustic wave (BAW)-based actuation, which suppresses Rayleigh streaming effects on the submicron particles. We demonstrate, for the first time, a continuous-flow acoustophoretic separation of 300-nm and 100-nm particles in our device with a separation efficiency of 86.3%. We also present an analytical stochastic method to model the transport of submicron particles in the...