Wet adhesion between two soft layers.

Two solids can adhere to each other in the presence of a liquid bridge between them, which is called wet adhesion. When the solid is soft, the liquid bridge can cause deformation in the material, and in turn, the deformation may have dramatic effects on the wet adhesion. To investigate the effect, in this article, we calculate the deformation in two soft layers with different separations and connected by a liquid bridge. We illustrate the effect of deformation in the soft layers on the adhesive force. For a given liquid volume and separation between the two layers, the adhesive force increases dramatically by decreasing the elastic moduli of the soft layers. We also discuss the contact between the two soft layers due to the deformation caused by the liquid bridge. Depending on the volume of the liquid bridge, the two layers may be in contact with each other at the center of the wetting area or some other locations between the center and the contact line. The results may improve current understanding of wet adhesion between soft materials and have potential applications in designing and fabricating soft devices and structures.