Simulation analysis on surface morphology and superior adhesive properties of honeybee footpad

Many animals adhere to surfaces with their toes or footpads. To achieve adherence, honeybees have evolved unique footpads. The adhesion movement involves the unfolding adhesion and contraction desorption of the footpad on the contact surface. We characterized honeybee footpad adhesion by phenotypic analyses and a simulation approach. As determined by stereomicroscopy and scanning electron microscopy, when bonded, the honeybee footpad resembled an unfolded flat plate. Adhesion resulted from the unfolding of the honeybee footpad and fluid secretion from the footpad. In conjunction with these observations, a modeling approach (using Surface Evolver) was used to evaluate the micro/nanostructure of the honeybee footpad during wet adhesion. Different slenderness ratio models revealed the strength of honeybee adhesion force. Then, using an imitation centrifugal test stand, an adhesion force of 11.5 times the weight of the honeybees was detected and compared to the modeling results. These results indicated that the superior adhesion properties of honeybees were a result of the combined effect of the footpad micro/nanostructure and the liquid bridge.