The goal of this experimental study is to quantify the spreading of parallel streams with viscosity contrast in multilayer microfluidic flows. Three streams converge into one channel where a test fluid is sheathed between two layers of a Newtonian reference fluid. The test fluids are Newtonian fluids with viscosities ranging from 1.1 to 48.2 cP and suspensions of 10-μm-diameter PMMA particles with particle volume fractions φ = 0.16-0.30. The fluid interface locations are identified through fluorescence microscopy. The steady-state width of the center stream is strongly dependent on the viscosity ratio between the adjacent fluids and exhibits a near power-law relationship. This dependence occurs for both the Newtonian fluids and the suspensions, although the slopes differ. The high-concentration suspension (φ = 0.30) diverges from Newtonian behavior, while the low-concentration suspensions (φ = 0.16, 0.22) closely approximate that of the Newtonian fluids. The observed suspension behavior can be attributed to shear-induced particle migration.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry