Walter M. Presz

Macro-scale acousto-fluidics using bulk ultrasonic standing waves

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 prese...

Acoustic edge effect: Novel acoustophoretic cell retention to enable continuous bioprocessing

There is currently a shift in Bioprocessing towards continuous manufacturing of monoclonal antibodies or recombinant proteins in perfusion mammalian cell cultures (Konstantinov & Cooney, Journal of Pharmaceutical Sciences, 2015). A cell retention device is the key technology component that enables the shift to continuous production. A novel acoustic cell retention device operates by continuously drawing off a harvest flow, equal to the perfusion rate of the bioreactor, while recirculating the retained cells back to the bioreactor. The harvest flow path is tangent and significantly smaller than the recirculation rate. The device utilizes a novel acoustophoretic effect known as an “acoustic edge/interface” effect in conjunction with a recirculating flow beneath the acoustic harvest chamber which collects and returns cells to the bioreactor. This interface effect operates by creating a radiation pressure/force field at the interface between cell-free harvest and cell-laden circulating fluids. Numerical resul...

Macroscale angled ultrasonic standing waves: A novel approach for particle manipulation

Macro scale acoustophoretic devices use radiation forces to trap particles inside a standing wave to separate them from a mixture in a continuous fashion. However, these devices are limited by factors such as flow rates, residence times, and temperature rise which could be detrimental for certain applications. A novel method of separating, sorting and differentiating various particles using bulk angled ultrasonic standing waves is presented. This technique offers very sensitive separation capability with respect to size and acoustic contrast of particles. Universal curves are developed for particle deflection from the bulk flow direction at all wave angles as a function of a non-dimensional parameter defined by the ratio of acoustic radiation force to viscous drag force. Both CFD (Computational Fluid Dynamics) and model test data verify the analytical predictions. New macro-scale, ultrasonic separator concepts are presented that use the angle wave technology to effectively deflect and/or separate microcar...

Macro-scale cell manipulation using bulk ultrasonic standing waves for biopharmacy and cellular therapy applications

Acoustic standing wave fields are widely used in MEMS applications to manipulate micron sized particles in fluids with typical fluid channel dimensions of half a wavelength. This report presents three novel acoustofluidic platforms for particle separation and/or manipulation at macroscale, i.e., tens to hundreds of wavelengths. The first platform uses multidimensional standing waves which generate lateral radiation forces that trap and tightly cluster suspended fluid or particulate, enhancing the gravitational settling effect that results in continuous, macroscale separation. The second platform employs acoustic radiation forces generated near the edge of an acoustic standing wave to hold back particles and generate a wall type separation effect. The third platform uses the acoustic radiation forces generated by a macroscale, angled standing wave to deflect particles in a controlled fashion for particle manipulation and/or differentiation. Applications are focused in biopharmacy and cellular and gene ther...