Stagnation flow of polymer solutions in a T-shaped microchannel

Viscoelastic flow of polymer solutions opposingly flowing through a T-junction has been a subject of interest for particle manipulation and droplet-based microfluidics lately. Some studies have been conducted on the non-Newtonian fluid dynamics near the stagnation point at the junction, which eventually can dictate the efficacy of those microfluidic operations. However, a systematic understanding of the fluid rheological responses, namely different combinations of shear-thinning and elasticity, is still lacking in such circumstances. In this work, we experimentally investigate the responses of different rheological properties of polymer solutions symmetrically and opposingly flowing through a planar T-junction microchannel. The flow visualization results indicate that the flow regimes can be expected to be either vortex dominated or having unstable streamlines, depending on the strength of elasticity and shear-thinning of the fluid under such flow conditions.