Relationship of hydration and nanomechanical characteristics of beetle cuticle

Abstract

Insect elytra cuticle has some excellent mechanical properties, such as tenacity, waterproofness and light weight, which are the results of its laminate composite structure. Understanding the unique structural and mechanical characteristics of the elytral cuticle of beetles will facilitate the design of biomimetic composite materials. As the thickness of beetle cuticle can range from the microscale to the nanoscale, investigating the cuticle’s mechanical characteristics is difficult until nanoindentation techniques have been developed. In this study, a nanoindenter was used to explore nanomechanical characteristics, including the reduced modulus (E r) and hardness (H), of the cuticle of the dung beetle Copris ochus Motschulsky. To understand the effect of water on these characteristics, the samples were tested immediately after collection or after different periods of sample ageing. The results showed that the mechanical characteristics were strongly influenced by sample ageing and that E r and H increased with decreasing water content. The results are discussed in the context of how the mechanical characteristics of the cuticle correspond to beetle behaviour.