The microstructure morphology on ant footpads and its effect on ant adhesion

Ants show a bionic application prospect due to their special climbing ability. However, different ant species living in different environments exhibit different adhesion abilities. In order to reveal their mechanical mechanisms, footpads of four representative ant species are investigated experimentally. Regular microstructures on the ventral side of ant footpads are clearly observed, which possess different shapes and sizes for different ant species. The normal adhesion force for each kind of ant is further measured with a spinning technique, which is significantly affected by the microstructure on the ventral surface of ant footpads. Theoretical models are established in order to disclose the mechanical mechanism, in which both the capillary force and the van der Waals interaction are considered. It is found that the real contact area depends significantly on the microstructures on the ventral side, which further affects the total adhesion force. The coexistence mechanism of wet and dry adhesion for ant footpads is proposed. The finding in the present paper should be useful for deep understanding of the adhesion mechanism of different ant species and helpful for the design of bio-inspired intelligent adhesion surfaces.