Investigating the nanomechanical properties and reversible color change properties of the beetle Dynastes tityus
- 402 Downloads
The wing cases (elytra) of Dynastes tityus are able to change coloration from yellow-green in a dry state to deep brown in a wet state due to different degrees of water absorption. An environmental scanning electron microscope was used to investigate the elytra’s reversible color change properties. Because the elytra cuticle has a spongy structure that is composed of laminated chitin and protein, a UV–Vis–NIR spectrophotometer was used to investigate the elytra’s optical properties. The width of the curve peak gradually decreased from 60 to 10 nm when the color of the elytra varied from deep brown to yellow-green. In a humid environment, air between the voids was replaced by water with a higher refractive index that induced an elytra color changed from yellow-green to deep brown. Interestingly, when both humidity and elytra color changed, the elytra’s mechanical properties varied too. When the humidity of the environment changed from 100 to 34%, the reduced modulus (E r) and hardness (H) of the elytra increased 230 and 440%, respectively. The storage modulus (E′) of the elytra is 1.98 ± 0.65 and 1.17 ± 0.22 GPa in yellow-green and deep brown color at 10 Hz, respectively, while their loss modulus (E″) is similar. tan δ of deep brown elytra is 0.072 ± 0.017, which is nearly two times higher than that of yellow-green. It can be demonstrated that when the elytra’s color turns to yellow-green, they are more elastic with less energy loss. The relationship between the elytra’s mechanical properties and structure color will not only help us gain insight into the biological functionality of the color change but also inspire the designs of artificial biomimetic devices.
KeywordsColor Change Color Statement Nanomechanical Property Insect Cuticle Spongy Layer
This work was supported by National Natural Science Foundation of China (No. 31672348), China-EU H2020 FabSurfWAR Project (No. S2016G4501 and 644971), and by 111 Project (B16020) of China.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 10.Vigneron JP, Pasteels JM, Windsor DM, Vértesy Z, Rassart M, Seldrum T, Dumont J, Deparis O, Lousse V, Biró LP, Ertz D, Welch V (2007) Switchable reflector in the Panamanian tortoise beetle Charidotella egregia (Chrysomelidae: Cassidinae). Phys Rev E: Stat Nonlinear Soft Matter Phys 76(3 Pt 1):031907CrossRefGoogle Scholar
- 16.Rassart M, Simonis P, Bay A, Deparis O, Vigneron JP (2009) Scale coloration change following water absorption in the beetle Hoplia coerulea (Coleoptera). Phys Rev E 80(1):1957–1974Google Scholar
- 27.Gu CJ, Katti DR, Katti KS (2015) Dynamic nanomechanical behaviour of healthy and OI human cortical bone. Bioinspir Biomim Nan 4(1):15–25Google Scholar
- 32.Prokop ME (1969) Longevity and color change in the rhinoceros beetle, Dynastes tityus L. (Coleoptera: Scarabaeidae). Coleopter Bull 16(1):33–42Google Scholar
- 36.Hariyama T, Takaku Y, Hironaka M, Horiguchi H, Komiya Y, Kurachi M (2002) The origin of the iridescent colors in coleopteran elytron. Forma 17:123–132Google Scholar
- 40.Hillerton JE, Reynolds SE, Vincent JFV (1982) On the indentation hardness of insect cuticle. J Exp Biol 96:45–52Google Scholar
- 45.Rinaudo M (2006) Chitin and chitosan: properties and applications. ChemInform 38(27):61–90Google Scholar
- 51.Ferry JD (1980) Viscoelastic properties of polymers, 1st edn. Wiley, New YorkGoogle Scholar