Microtribology of biological materials

This paper presents a study on friction and indentation of attachment pads of the great green bush cricket, using a system involving a biological material and a flat surface. The pads are evolutionarily optimized frictional devices that are adapted to attach the insect to a variety of natural surfaces. The attachment pads of both living and dead insects were tested and evaluated using several analysis techniques. These techniques included friction analysis by microtribometry, microindentation, scanning electron microscopy (SEM), histologic sectioning, and shock freezing. Microtribological analysis showed that the friction between pad and surface is anisotropic. The anisotropy increases with increasing normal force. Microindentation revealed that the pads respond very flexibly to applied loads leading to an optimized morphology with respect to contact area. All results make clear that the microtribological properties are a perfect combination of surface structure, lubrication and active interface control.