Effect of relative humidity on the peeling behavior of a thin film on a rigid substrate

A modified Kendall's model is established in order to investigate the effect of relative humidity on the peeling behavior of a thin film adhering on a rigid substrate. When the humidity is less than 90%, a monolayer of water molecules adsorbed on the substrate surface induces a strong disjoining pressure at the interface, which can significantly enhance the steady-state peel-off force. When the humidity is greater than 90%, water molecules condense into water droplets. Four different peeling models are established on this occasion, depending on the surface wettability of the film and substrate. It is found that the steady-state peel-off force is either enhanced or reduced by the water capillarity comparing to the dry peeling model. The results can be used to understand gecko adhesion in humid environment.