Trapping microfluidic drops in wells of surface energy

Rémi Dangla, Sungyon Lee, Charles N. Baroud

Research output: Contribution to journalArticlepeer-review

69 Scopus citations


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

Original languageEnglish (US)
Article number124501
JournalPhysical review letters
Issue number12
StatePublished - Sep 15 2011

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