Silkworm cocoon as natural material and structure for thermal insulation

Silkworm cocoons are important biological materials that protect silkworms from environmental threat and predator attacks. Silkworm cocoons are able to provide significant buffer against temperature changes outside of the cocoon structure. We present our investigation of the thermal insulation properties of both domestic and wild silkworm cocoons under warm conditions. Wild cocoons show stronger thermal buffer function over the domestic cocoon types. Both the cocoon walls and the volume of inner cocoon space contribute to the thermal damping behaviour of cocoons. Wild silkworm cocoons also have lower thermal diffusivity than domestic ones. Calcium oxalate crystals affects the thermal behaviour of wild silkworm cocoons, by trapping still air inside the cocoon structure and enhancing the thermal stability of the cocoon assembly. The research findings are of relevance to the bio-inspired design of new thermo-regulating materials and structures.