(6ag) Microfluidic Studies of Emulsions and Suspensions in Wall-Bounded Shear Flow

Authors: 
Khalkhal, F., University of California at Berkeley
Muller, S. J., University of California at Berkeley

Microfluidics provide a promising platform to study a wide range of phenomena from fluid flow analysis to individual and collective cell behaviors. In my ongoing research, I am pursuing a fundamental study on the dynamics of individual double emulsion droplets in a wall-bounded shear flow. Initially, monodisperse double emulsion droplets of water in oil in water are generated with a diameter in the range of ~ 100 um and polydispersity index (PDI) of 1.002 in a flow focusing device by controlling the flow rate ratios. Using a capillary micromechanics approach, the droplets are shown to be very deformable. My preliminary experiments reveal that double emulsions are focused to a certain distance from the wall while traveling down the microcapillary channels at low Re numbers (Re <1). The equilibrium position in the channel and the entry length required to achieve that position is being determined. In parallel, I am working on an industrially funded project to study viscoelastic entry flow phenomena in microfluidic abrupt contractions. It was observed that vortices of different lengths form at various Re and elasticity numbers. Micro-Particle Image Velocimetry (µ-PIV) is used to analyze flow at the upstream and in the constriction. The experimental results are compared with 3D simulations in Comsol Multiphysics.