Macro-scale acousto-fluidics using bulk ultrasonic standing waves

Abstract

Macro-scale acousto-fluidics involves the interaction between acoustic radiation force exerted on a particle by bulk acoustic standing waves spanning many wavelengths, fluid drag force, and the gravitational force of the particle. Parameters are particle size, and ratio of particle to fluid density and particle to fluid compressibility. Different acousto-fluidics configurations can be used to manipulate particles in multiple ways. In cell clarification, the configuration is that of a depth flow filter with the added benefit of separating the cells out of the acoustic field, thereby eliminating any issues with filter clogging or fouling. In perfusion of stirred bioreactors, the configuration resembles that of a tangential flow filter. In a third configuration, the bulk acoustic standing wave is angled relative to the fluid velocity resulting in a label-free fractionation tool. Several underlying theoretical and numerical results of acoustic radiation force and particle trajectory calculations will be presented. A theoretical framework to calculate the acoustic radiation force on spherical, spheroidal, and cylindrical particles has been developed for any particle size relative to wavelength. An analytical solution for particle deflection angle in a planar angled standing wave and uniform flow has been developed. Experimental results will be shown to support the theory.