Trapping microfluidic drops in wells of surface energy.

摘要: A small hole etched in the top of a wide microchannel creates well surface energy for confined drop. This produces an attractive force ${F}_{\ensuremath{\gamma}}$ equal to gradient, which is estimated from geometric arguments. We use drag ${F}_{d}$ outer flow probe trapping mechanism. When ${F}_{d}l{F}_{\ensuremath{\gamma}}$, drop deforms but remains anchored hole. Its shape provides information about pressure field. At higher velocities, detaches, defining critical capillary number ${F}_{d}={F}_{\ensuremath{\gamma}}$. The measured anchoring agrees with model.