Title: Elastocapillary phenomena with thin films

Speaker: Dr. Deepak Kumar, UMass Amherst

Abstract: Many liquid phase technologies require the encapsulation of one liquid in another. In the stabilization of emulsions, drug delivery, and remediation of oil spills, liquid droplets are separated from the surrounding liquid by a fluid monolayer of molecular or particulate surfactants. By contrast, we typically wrap solid contents, such as chocolates or the filling in a dumpling, with solid elastic sheets. I will present our work on a new class of surfactant based on thin elastic sheets that can wrap liquid drops in a spontaneous process driven by capillary forces.

I will show a method where we can exploit the fast dynamics of droplet impact to achieve wrapping of oil droplets by ultrathin polymer films in a water phase or vice versa. The process yields wrappings that are optimally shaped to maximize the enclosed fluid volume and have near-perfect seams. We can achieve wrappings of targeted three-dimensional (3D) shapes by tailoring the 2D boundary of the films. I will further address the related fundamental question about the nature of capillary forces acting on thin films adsorbed to a liquid surface, more specifically the role that solid surface energies play in determining the surface stress.