Multiphase Flow Through Hairy Channels

Surfaces textured with long, flexible fibers are ubiquitous in nature and often serve vital functions in multiphase systems. Cilia in lung epithelia transport mucus along airways, while the fur of semiaquatic mammals entrains air for insulation while swimming. Inspired by their versatility, we fabricate “hairy” elastic surfaces by casting a curing elastomer in laser-cut acrylic molds. Specifically, we apply arrays of deformable posts in model systems for the displacement of immiscible phases in a Hele-Shaw cell patterned with elastic features, wherein the buckling of the obstacles modifies the local geometry and thus has a strong effect on drainage. By displacing the oil with water at Ca<<1, we study the geometry and contact line dynamics of the evolving interface and the impact of confinement on oil removal. Models for depth-averaged fluid flow and the deflection of elastic beams are adapted to our problem to describe the deformation of the host medium due to interfacial and viscous forces. We find the oil phase captured in bundles, in quantities that differ significantly from the undeformed reference case; this has implications towards both enhanced oil recovery and the development of liquid-infused surfaces, which possess properties such as omniphobicity and drag reduction.