Structural and nanomechanical insights into the spicules of Euplectella aspergillum

Abstract Biomimicry offers sustainable, efficient, and adaptable solutions inspired by natural systems. The skeleton of Euplectella aspergillum (EA) represents a highly optimized biological structure. It is composed of silica-based elements known as spicules, which interlock to form a lattice-like framework that provides strength and flexibility. In this study, the structural and functional properties of EA spicules were investigated. The macrostructure revealed a well-organized, multi-component framework consisting of a filter cap, spiral crest, skeletal wall, and anchor base—features that contribute to hydrodynamic efficiency and mechanical stability. The hierarchical architecture was characterized using scanning electron microscopy, atomic force microscopy (AFM), nanoindentation, thermogravimetric analysis, differential scanning calorimetry, and x-ray diffraction (XRD). At the microscale, spicules exhibited a laminated architecture of silica and organic layers, which redirect crack propagation and dissipate energy, enhancing fracture resistance. Nanoindentation and AFM revealed mechanical properties across the spicule cross-section, with an average hardness of 4.436 ± 0.202 GPa, reduced modulus of 39.596 ± 0.374 GPa, and stiffness of 21.200 ± 0.517 µ N nm −1 . Sink-in behavior indicated the elastic and brittle nature of both silica and organic regions. Localized pile-up near organic interfaces highlighted plastic deformation constraints due to mechanical heterogeneity. Thermal analysis identified approximately 9.83% organic content and confirmed high thermal stability of the silica matrix. A crystallization event occurring at approximately 1090 °C corresponded to the transformation of amorphous silica into β -cristobalite, as confirmed by XRD. These findings provide insights into the structural and mechanical properties of EA skeleton, supporting the design of high-performance ceramic materials with enhanced mechanical properties for bioengineering applications.