Scaling effects of wet adhesion in biological attachment systems.

Insects have evolved fibrillar attachment devices based on wet adhesion to attach themselves to a variety of surfaces. This paper investigates the scaling effects of wet adhesion mediated by a liquid bridge between a fiber and a solid surface. The influences of liquid volume and contact angles are discussed via a scaling law indicating that the adhesive strength can be enhanced by contact size reduction. Due to the maximum negative pressure in the liquid bridge, there exists a critical length scale at which the system achieves the theoretical tensile strength of the liquid. We conclude that size reduction down to a critical scale results in optimization of the adhesive strength.