Micro/Nanoscale Tribological and Mechanical Investigation of the Articular Surfaces of Katydid Leg Joints: Potential for the Novel Bioinspired Lubrication Systems

Abstract

Insects are recognized with their ability to efficiently move, operate, and function, and hence are inspiration for the design of micromechanical systems. This work deals with the structural, mechanical, and frictional characterization of the leg joint articulations of the katydid (Orthoptera: Tettigoniidae). For the katydids, the tibia joints were found to show a nanosmooth texture while the femur joint had a micro/nanotextured surface characteristics. The nanotexture was a two-tone periodic patterns with the hierarchical structures involving cylindrical ridges that are covered with nanoscale lamellar patterns perpendicular to the long axis and valleys between ridges that are decorated with the hillock patterns. The tibia and femur contact regions showed the reduced elastic modulus (Er) values ranging from 0.88 ± 0.01 GPa to 3.90 ± 0.11 GPa. The friction coefficient (μ) value of 0.053 ± 0.001 was recorded for the sliding contact of the tibia joint against the femur joint in air under dry conditions. The low friction values are attributed to the reduced real area of contact between the joint pair due to the coupling of the nanosmooth surfaces against the hierarchically nanotextured surfaces.