Microfluidic breakups of confined droplets against a linear obstacle: The importance of the viscosity contrast

Abstract

To cite this version:Louis Salkin, Laurent Courbin, Pascal Panizza. Combining experiments and theory, we investigate the break-up dynamics of deformable objects, such as drops and bubbles, against a linear micro-obstacle. Our experiments bring the role of the viscosity contrast η between dispersed and continuous phases to light: the evolution of the critical capillary number to break a drop as a function of its size is either nonmonotonic ( η > 0) or monotonic ( η 0). In the case of positive viscosity contrasts, experiments and modeling reveal the existence of an unexpected critical object size for which the critical capillary number for breakup is minimum. Using simple physical arguments, we derive a model that well describes observations, provides diagrams mapping the four hydrodynamic regimes identified experimentally, and demonstrates that the critical size originating from confinement solely depends on geometrical parameters of the obstacle.

Lamella Division in a Foam Flowing through a Two-Dimensional Porous Medium: A Model Fragmentation Process

“…1). It is reminiscent of the fragmentation on an obstacle of drops or bubbles confined in microchannels [20,21]. No fragmentation in a higher number of fragments was observed, nor other fragmentation processes; in particular, the snap-off of films [12,13] does not occur in our experiments because the pore size is much larger than the soap films coating them.…”

Path selection rules for droplet trains in single-lane microfluidic networks

“…In all experiments, the Reynolds and the capillary numbers are very small and span the ranges 10 −3 −10 −1 and 10 −3 −10 −2 , respectively. For this range of capillary numbers and any values of D, we do not observe droplet breakup nor collision between drops at any T junctions of the circuit [21,25,[36][37][38][39][40]. Figure 16 shows the three hydrodynamic regimes found experimentally as λ varies when either L eq <L 3 or L eq >L 3 .…”

Effect of confinement on the deformation of microfluidic drops

“…A few experiments have been conducted to study the deformation of squeezed drops in microchannels [11][12][13]. However, these studies remain very qualitative and a more quantitative description of the role of confinement in the deformation of drops is still lacking.…”