Numerical studies of geometry effects of a two-dimensional microfluidic four-roll mill on droplet elongation and rotation

Numerical simulations of vesicle and bubble dynamics in two-dimensional four-roll mill flows

“…The constant value of the long axis in the stable state of the bubble decreases as the surface tension increases, as indicated in the lower panel of Fig. 14 [2,24].…”

“…When the flow is purely extensional (ξ = 1) with the flux ratio f = 1, the bubble can extend with the inclination angle being fixed at around π/4. The deformation of droplets in the extensional flow has long been studied [2][3][4]24,51,52]. tension is too small, the bubble cannot resist the extensional deformation of the flow and elongates in time, gets thinner, and finally breaks up (Fig.…”

“…1. Since this microfluidic four-roll mill device enjoys a strong capability to produce various flows, it has been used * kimy@cau.ac.kr to study the tumbling dynamics of DNA [21], the transition among tank-treading, trembling, and tumbling motions of a vesicle [22], the complex dynamics of deforming droplets in the creeping flow [23], and the elongation and rotation of a droplet [24].…”

“…The inextensibility of the vesicle, which resists both the tangential and normal force, plays a significant role in the tumbling motion of the vesicle. When the flux ratio increases in the positive direction, the magnitude of a deformation (or extensional) tensor increases, which induces an elongation and sometimes a breakup of a bubble [24].…”

Simple microfluidic stagnation point flow geometries

“…27 The effects of the dimensions of their geometry as well as the volume flow rate on the elongation and rotation of droplets were investigated by a 2D spectral boundary element method. 28 The aforementioned designs require precise and rather elaborate pressure control over six or eight in-and outlet streams to obtain a stable flow. This complicates the set-up in practice and requires an active feedback loop.…”