Microstructural characteristics and nanomechanical properties of hindwings of the Asian ladybeetle, harmonia axyridis

The hindwings are thin and fragile. However, they can display countless folding/unfolding actions during their lifetime. At the root of the Asian ladybeetle (Harmonia axyridis) hindwings, three thicker veins spread out. In this study, laser scanning confocal microscope (LSCM) was used to acquire the cross-section microstructures of the three thinker main veins. And it was found that the thickness of dorsal side (DS) and ventral side (VS) are different. The irregularly shaped vein chambers are observed from the cross-section microstructure of the three veins. Then the reduced modulus (Er) and hardness (H) of DS and VS were investigated along the veins varying from wing base to the region of principal transverse fold by nanoindentation. All the Er and H appear a tendency of linear increasing. In the folding region, the Er and H of DS were larger than that of VS. The results will be useful to the design of new deployable MAV and bioinspired systems.