Self-Pinning on a Liquid Surface

We report on the first experimental
evidence of a self-pinning
liquid drop on a liquid surface. This particular regime is observed
for a miscible heavier oil drop (dichloromethane) deposited on an
aqueous solution laden by an ionic surfactant (hexadecyltrimethylammonium
bromide). Experimental characterization of the drop shape evolution
coupled to particle image velocimetry points to the correlation between
the drop profile and the accompanying flow field. A simple model shows
that the observed pinned stage is the result of a subtle competition
between oil dissolution and surfactant adsorption.