Bubbles in Complex Microgeometries
Stony Brook University
Images by M. Sauzade and T. Cubaud/Stony Brook University
Multiphase flows in confined geometries can exhibit a variety of intriguing morphologies. At the small scale, the unique balance of forces produces flow patterns that are typically governed by viscous and capillary effects. While surface tension tends to minimize interfacial area with bubbles having spherical shape, viscous laminar flows can also strongly deform bubbles in velocity fields set with the channel geometry. Here, the deformation of capillary surfaces is accentuated with the use of a highly viscous carrier fluid (viscosity: 1,000 cS) and the presence of circular cavities along a square microchannel (h = 250 um) for smoothly modulating flow velocity. In such viscous-dominated regime, air bubbles adopt a range of shapes depending on their size and packing. In particular, when passing through a series of extensions and constrictions, bubbles are observed to strongly elongate in accelerating flow regions and swell in decelerating flow fields. These experiments illustrate the possibility to control the flow morphology of microbubbles through the interplay between channel geometry and viscous flow.
This material is based upon work supported by the National Science Foundation under Grant no. CBET-1150389
This image may be freely reproduced with the accompanying credit: M. Sauzade and T. Cubaud (Stony Brook University)