Stiffness-based cell sorting using power-law fluids in ridged microchannels*

Sorting biological cells in heterogeneous populations is a critical task required in a variety of biomedical applications and therapeutics. Microfluidic methods are a promising pathway towards establishing label-free sorting based on cell intrinsic biophysical properties, such as cell deformability. Experiments and numerical studies show that microchannels decorated with diagonal ridges can be used to separate cell by stiffness in a Newtonian fluid. In an effort to increase the throughput and enhance sorting resolution, we leverage the shear dependent viscosity of non-Newtonian fluids. Using numerical simulations, we probe the stiffness-based sorting of compliant cells in ridged microchannels filled with a shear-thinning power-law fluid. We consider compliant cells with a range of capillary numbers and examine the effect of ridge geometry on cell trajectories in microchannel. Results reveal shear-thinning fluids can be used to enhance sorting resolution of deformable cells.