Micro/Nanoscale Tribological and Mechanical Investigation of the Articular Surfaces of Katydid Leg Joints: Potential for
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Micro/Nanoscale Tribological and Mechanical Investigation of the Articular Surfaces of Katydid Leg Joints: Potential for the Novel Bioinspired Lubrication Systems Jun Kyun Oh1, Cengiz Yegin1, and Mustafa Akbulut1,2 1 Department of Materials Science and Engineering, Texas A&M University, College Station, TX 77843, U.S.A. 2 Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, U.S.A. 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. INTRODUCTION Through the evolution of millions of years to thousands of years, the natural species have developed optimized multifunctional composite materials and geometric structures to achieve efficient functions and operations required in their lifespan [1,2]. Biotribology is one of the fastest-growing research areas of the science and engineering dealing with all aspects of tribology derived from the biological systems [3]. Studying materials based on the biological systems is to offer useful clues and design motifs for developing new materials for various engineering applications [4,5]. Biomimetic materials are of great interest in the field of tribology, which seeks to develop novel lubrication systems and coating for enhanced efficiency and durability [6]. In this work, we have investigated the articular surfaces of the katydid joints and gained some insights into why insect legs function durably and effectively. The results from the fundamental analysis and characterization showed that the tibial and femoral articular surfaces indeed exhibit the promising tribological and mechanical properties due to very sophisticated hierarchical structures. The investigation was carried out by high resolution imaging and
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