Modeling and Experiments on Liquid-Infused, Mechanically Activated Porous Materials

The goal of our research is to develop new understanding regarding the design and fabrication of mechanically activated liquid-infused porous films. Our unique approach is to consider a thin, elastic material that features well-defined pores, which are plugged with an infusing liquid that preferentially wets to the walls of the pores. By tuning the geometry of the pores, liquid-filled pores can be rearranged into a configuration that creates an open pore by applying stretch to the solid material, and they close (i.e. heal) again when the stretch is removed. Impregnating the pores with liquid seeks to avoid limitations that prevent complete pore closure and allows for tailoring of the pore geometry to drive liquid redistribution in the pore. The specific objective of this research is to study the effects of pore geometry and liquid wetting for creating fully reversible, stretch-activated pores. Our approach is both computational and experimental: Surface Evolver software is utilized to predict minimal energy wetting states of liquid in various pore shapes, and experiments on porous elastomers infused with either water or mineral oil allow measurements of stretch-induced changes in wetting properties and porosity. Both modeling and experiments demonstrate that a tear-shaped pore, which consists of a circular pore that features a taper extending in a radial direction, can enable reversible opening and closing of the pore via liquid redistribution. Our results indicate that infusing liquids with lower surface tensions and lower contact angles on walls of the pore exhibit better reversibility during the application of stretch.