Microfluidic acoustophoretic cell/particle separation has gained significant interest recently. The motion of cells/particles in acoustophoretic separation is commonly analyzed by using a one-dimensional (1-D) analytical model in a "static" fluid medium, while the effects of acoustic streaming, viscous boundary layers, and 2-D/3-D geometries are usually not considered. This makes it challenging to accurately predict the motion of cell/particles. Here a numerical modeling method for accurately analyzing the acoustophoretic motion is presented by including the aforementioned effects in the model. The first-order pressure and the second-order streaming velocity are first calculated by using a higher-order finite difference method. Then, acoustophoretic force is calculated based on the force equation proposed by Gorkov and is applied to the Newton's second law to calculate the acoustophoretic motion. The effects of acoustic streaming, viscous boundary layers, and 2-D geometry on the motion of cells/particles are studied by comparing them to 1-D modeling results. Since the acoustophoretic motion depends on the vibro-acoustic properties (e.g., density, compressibility, and size) of particles/cells, these properties can be estimated by optimally fitting the experimental and simulated trajectories. The properties of polystyrene beads obtained from experimental results through the presented numerical analysis show good agreement with data reported in literature.

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