Imbibition in gel-coated capillary tubes

The surface tension of a droplet can deform a soft solid, resulting in the formation of a wetting ridge around the contact line. As a result, the motion of a partially wetting drop on a soft visco-elastic gel can cause dissipation in the solid. To study the influence of a soft substrate on the imbibition of a partially wetting fluid, we produce capillary tubes coated with silicone gel. Depending on the thickness of the gel layer, the gel precursor is deposited on the inner wall by spin coating or high-speed rotation around the axis of the tube. We characterize the imbibition rate for different tube diameters, gel thicknesses, and fluid properties. Our results indicate two imbibition regimes: at low gel-thickness, the dissipation is negligible; at high gel-thickness, the gel deformation influences the motion of the contact line and the imbibition rate.