关键词: Cuticle, Multilayer, Angle-dependence color-changing, Nanomechanical properties, Coupled bionic

Abstract: The architecture of multilayer acting in colorful appearance has been widely reported. In spite of this, it is interesting that dense multilayer in epicuticle for Popillia indgigonacea Motsch elytra not only helps presenting angle dependence color-changing, but also showing higher reduced modulus (Er) and hardness (H) to protect soft abdomen below. The optical and nanomechanical properties of elytron were investigated by structural observation, optical experiments, nanoindentation and coupled bionic model simulations. The peak reflectance gradually varies from 588 nm to 510 nm with color change from orange and yellow to green when the incidence angle switches from 0° to 60°, which is attributed to the regulated variation from refractive spectra between the layers in different angle. In addition, the relatively higher Er and H of elytron epicuticle and endocuticle could play a role in resisting force with its multilayer. To identify the multifunctional characteristics of multilayer, optical and mechanical simulations were conducted based on coupled bionic models, and a strong consistence between the experiments and simulations is obtained. The multilayer could resist force with lowest strain and stress, and the structural thickness is the most necessary factors that could adjust the colors in color-changing process.

Key words: Cuticle, Multilayer, Angle-dependence color-changing, Nanomechanical properties, Coupled bionic