From bio-waste to biomaterials: The eggshells of Chinese oak silkworm as templates for SERS-active surfaces

Although over 80% of the world’s existing animal species are insects, with each of these species having unique eggshell morphologies, limited information is available regarding the use of their eggshells in material science applications. The present research discusses using discarded eggshells of the Chinese oak silkworm (Antheraea pernyi) as a technological material. The 3-dimensional aspects of the insect’s eggshell were examined in detail, demonstrating the complexity of their novel surface morphology. The outer surface of the eggshell was comprised of a hexagonal structure, whereas the inner surface consists of a mostly smooth surface. Distinctive layers of the eggshell were observed when cross sections of the surface were analyzed. The elastic modulus of the inner part of the eggshell is substantially greater than that of the outer part. The physicochemical properties of the eggshell were characterized and no toxic properties were found. The hexagonal structures found on the outer surface of the eggshell provide a highly suitable template for silver nanostructure deposition. The resulting silver decorated surfaces can be used to detect molecules via surface-enhanced Raman scattering (SERS) effects. The deposition of silver renders the surface antimicrobial, whereas the original surface was microbial. Collectively, the insights gained in this study will be key in developing advanced engineering applications of the insect eggshells.