Simulation of a centrifugal microfluidic device for particle separation through acoustophoresis

Abstract

Particle and cell separation is a fundamental operation in biomedical research and clinical diagnostics. Circulating tumor cells (CTCs) separation is gaining interest because its detection and further study can help in early cancer diagnosis or provide guidance in chemotherapy treatment. Acoustophoresis in microfluidic devices has the potential to separate CTCs and rare cells from blood samples. This technology manipulates particles with acoustic waves and is a contact-free, label-free and highly sensitive technique. There has not been any experimental or computational study integrating acoustophoresis in centrifugal microfluidic platforms. This work presents the proof of concept of both principles for particle and cell separation, through the simulation of the device. A 3D FEM-based model was built in COMSOL for predicting the particles path. The geometry consisted first in a Surface Acoustic Wave based device with 2 pairs of IDTs located on top of a piezoelectric substrate, with a rectangular fluid channel with three inlets and three outlets. By applying boundary conditions, input parameters, and considering centrifugal, Coriolis, drag, lift and acoustic radiation forces; the particle’s paths are obtained. An attempt to validate the model with a previous experimental work was not successful since the acoustic pressure field was not generated correctly. However, the model was validated with a previous published simulation work of a non-centrifugal platform, and then used for computational demonstration of acoustophoretic separation of CTCs from white blood cells and red blood cells. A parametric analysis was performed to study the influence of five parameters on the efficiency of the device. Results showed that the recovery rate of CTCs at the center-outlet decreases when the angular velocity increases, when the distance to the axis of rotation increases, and when the distance between the IDTs and the channel increases. Recovery rate of CTCs at the center-outlet increases when voltage increases. Centrifugal platforms were found to be more sensitive to density variations. The model was modified to simulate a Bulk Acoustic Wave-based device and an attempt to validate it with a previous experimental work was done, however limitations were found. This work provides an understanding of the behavior of a centrifugal microfluidic platform with acoustophoresis and might be used as the initial reference for future computational work for correctly generating the acoustic pressure field and subsequently future experimental studies of particle and cell separation.