The Cheerios Effect under a thin elastic film

An air bubble placed in a liquid bath will rise through the bath until it reaches the liquid-air interface. The surface tension of the interface will keep the bubble from escaping into the air, but the bubble will in turn deform the flat interface. An equilibrium is reached between the buoyant force of the bubble and the surface tension of the liquid. Furthermore, an air bubble will move along the interface to reach a minimum in potential energy, in this case, the maximum height. Two bubbles in proximity to each other will attract each other due to the surface deformation from the other bubble. This mechanism is analogous to the famous Cheerios effect. Here, we examine the effect of replacing the liquid-air interface with a thin, elastic film. By floating a thin film onto the surface of a clean water bath, we can precisely place two monodisperse air bubbles below and observe the attraction between the bubbles, while altering the interface. We examine the effect of the thin film on the equilibrium position of the bubble as well as the attractive force between the two bubbles and present a theoretical model.