Capillary Flow of Oil in a Single Foam Microchannel

TL;DR

This study investigates how oil is drawn and transported through a single foam microchannel, revealing unique capillary and viscous dynamics and droplet formation mechanisms.

Contribution

It introduces a novel analysis of oil flow in foam channels, highlighting differences from classical porous media imbibition due to geometry effects.

Findings

Oil can be drawn into foam channels by capillary forces.

The scaling law differs from classical imbibition due to channel geometry.

Oil fragments into droplets after film breakup.

Abstract

When using appropriate surfactants, oil and aqueous foam can be intimately mixed without the foam being destroyed. In this Letter, we show that a foam, initially free of oil, can draw an oil drop under the action of capillary forces and stretch it through the aqueous network. We focus on the suction of oil by a single horizontal foam channel, known as a Plateau border. In such confined channels, imbibition dynamics are governed by a balance between capillarity and viscosity. Yet, the scaling law for our system differs from that of classical imbibition in porous media such as aqueous foam. This is due to the particular geometry of the liquid channels: Plateau borders filled with foaming solution are always concave whereas they can be convex or flat when filled with oil. Finally, the oil slug, confined in the Plateau border, fragments into droplets following a film breakup.