Trapping microfluidic drops in wells of surface energy

Rémi Dangla (1) , Sunyon Lee (1) , Charles N. Baroud (1)

1 LadHyX - Laboratoire d'hydrodynamique

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 ? 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 < F?, 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=F?. The measured anchoring force agrees with the geometric model. © 2011 American Physical Society.

Domains: Fluid mechanics [physics.class-ph]; Fluids mechanics [physics.class-ph]

Rémi Dangla, Sunyon Lee, Charles N. Baroud. Trapping microfluidic drops in wells of surface energy. Physical Review Letters, 2011, 107 (12), pp.124501. ⟨10.1103/physrevlett.107.124501⟩. ⟨hal-00998003⟩