Particle migration in the flow of polymer solutions through a serpentine microchannel

Serpentine microchannels have been frequently used in microfluidic devices for enhanced inertial focusing and separation of particles and cells with a reduced footprint. However, there are only a few studies on particle and cell manipulation in the flow of non-Newtonian fluids through serpentine microchannels. This work presents a systematic experimental investigation of both the individual and combined effects of fluid elasticity, shear thinning, and inertia on particle migration in a symmetric serpentine microchannel. Five types of polymer solutions, which have different rheological properties with various degrees of fluid elasticity and shear thinning, are tested along with a Newtonian solution. Each of these fluid rheological effects alone is found to accelerate the particle migration toward the channel centerline, leading to a significantly smaller threshold of Reynolds number than the inertial focusing. The combination of fluid elasticity and shear thinning may further enhance this centerline particle focusing or yield multiple equilibrium particle positions at both the centerline and corners.