Improving efficiency in acoustophoretic particle sorting: finite element modeling and experimental validation

This work presents a comprehensive approach combining computational modeling and experimental validation to study the interaction between standing surface acoustic waves (SSAWs) and micrometer-sized particles flowing in microfluidic devices designed for size-selective particle separation. The influence of key operational parameters - including flow rate and input voltage - was evaluated to assess their effect on polystyrene particle trajectories. In particular, particles with diameters of 6μm and 20μm were investigated, matching the size range of blood cells and typical biological particulates in biofluids. A three-dimensional finite element model was developed to simulate the propagation of surface acoustic waves on 128° YX-cut lithium niobate substrates and their coupling with the microfluidic structure. The model integrates piezoelectric, acoustic, and fluid dynamic domains, enabling the calculation of both acoustic radiation and hydrodynamic drag forces acting on suspended particles. The simulations provided insight into the balance between acoustic and viscous forces, allowing the identification of operating conditions that maximize size-based particle deflection. Experimental validation was carried out on devices fabricated via femtosecond laser micromachining of the master mold, followed by PDMS replication and plasma bonding. Fluorescence microscopy measurements of particle trajectories were used to quantify lateral displacement, showing good agreement with model predictions under the tested conditions. This integrated approach demonstrates the effectiveness of numerical modeling in guiding the design and optimization of SSAW-based microfluidic platforms. The consistency between simulation and experiment validates the accuracy of the developed model and supports its potential for advancing next-generation microfluidic devices in biomedical and analytical applications.