Wet Adhesion of Soap Bubble Bridge between Two Curved Surfaces

Abstract

Wet adhesion phenomenon of the soap bubble bridge is widespread in the climbing behaviors of geckos and insects, and the surface shapes generally have important impact on the adhesion behavior of soap bubble bridge. In order to focus on the effect of the shape on the wet adhesion, we study the adhesion behavior between two rigid surfaces containing different shapes such as concave, flat, and convex. For a given soap bubble bridge, the relationship between adhesion force and separation is numerically calculated, and the corresponding configuration of soap bubble bridge is also given. The results show that the adhesion force of soap bubble bridge decreases with the increase of separation. This trend is the same as the case of liquid bridge, although the volume of liquid bridge is constant while the volume of soap bubble bridge varies. The adhesion force with concave rigid surfaces is bigger than that of the other two kinds of rigid surfaces at the same separation. The wetting radius of the soap bubble bridge decreases with the increase of separation. The appearance of this phenomenon results from the equation of state for the gas in the soap bubble bridge. This research may improve the understanding of the mechanical mechanism of wet adhesion.