Structure-property relations in cuticular photonic crystals of different beetle groups (Insecta, Coleoptera)

H. Fabritius, X. Wu, A. Erbe, D. Raabe

Within the scope of this project, we analysed cuticular photonic crystals of beetle species from different taxonomic groups to evaluate and compare their design principles both experimentally and theoretically. The results show that ground beetle species (Carabidae) evolved multilayer structures in their epicuticle and scarab beetle species (Scarabeidae) helicoidal structures within their exocuticle. Weevils (Curculionidae) form three-dimensional photonic crystals with a bicontinuous cubic structure of the D- or diamond type in cuticular scales covering their exoskeleton. Modifications of structure and chemical composition of these materials enable different beetle species to generate optical properties adapted to their individual ecophysiological requirements.^[1]

Fig. 1. a) The neotropical weevil Entimus imperials. b) FIB-SEM sections and corresponding models of the photonic crystal structure in different domains of a scale from this weevil. Different orientations of the photonic crystal towards the incident light generate different colors. — Fig. 1. a) The neotropical weevil *Entimus imperials*. b) FIB-SEM sections and corresponding models of the photonic crystal structure in different domains of a scale from this weevil. Different orientations of the photonic crystal towards the incident light generate different colors.

© Max-Planck-Institut für Eisenforschung GmbH

Fig. 1. a) The neotropical weevil *Entimus imperials*. b) FIB-SEM sections and corresponding models of the photonic crystal structure in different domains of a scale from this weevil. Different orientations of the photonic crystal towards the incident light generate different colors.

© Max-Planck-Institut für Eisenforschung GmbH

References

[1] Wu, X., Erbe, A., Raabe, D. and Fabritius, H.-O.Extreme optical properties tuned through phase substitution in a structurally optimized biological photonic polycrystal. Adv. Funct. Mater. 23:3615-3620, 2013.