Transferring structure-mechanics correlations of biomaterials to artificial systems challenges scientists worldwide. One of these biomaterials is natural cuttlebone, the buoyancy tank found in cuttlefish (sepia). Its highly sophisticated aragonite-based microstructure is composed of parallel lamellas, which are supported by a regular array of interconnecting pillars. Owing to this defined structuring, natural cuttlebone achieves uniting an ultrahigh porosity (93 %) with an excellent mechanical stability (Young’s modulus of 1 MPa), two properties, which usually oppose each other. Even though cuttlebone is known for more than 180 years and its structure-dependent mechanical performance is well-established, only little work has thus far been devoted to mimicking this promising microstructure.
Here we report about a close-to-ideal replica of natural cuttlebone’s architectural features by ice-templating of aqueous vanadium pentoxide (V2O5) nanofiber solutions.1 The surface chemistry of the nanofibers and their pronounced mechanical flexibility enable the nanofibers to be shaped and arranged around the forming ice crystals, resulting in a highly sophisticated V2O5 nanofiber network within the frozen aqueous solution. Subsequent freeze-drying leads to self-supporting cuttlebone-like V2O5 nanofiber scaffolds with a remarkable porosity of up to 99.8 %. As compared to other V2O5 nanofiber scaffolds, which feature a random structuring, such cuttlebone-like scaffolds exhibit a clearly enhanced mechanical stability. Moreover, variation in V2O5 nanofiber concentration allows tailoring the lamella thickness, which in turn tunes the scaffolds’ mechanical properties.
The use of flexible V2O5 nanofibers unlocks further mechanical properties, going beyond bio-inspiration. Unlike other ceramic cellular solids, the here presented V2O5 exhibit a pronounced mechanical flexibility, which allows to reversibly compress the scaffolds up to 3 % and leads to remarkable damping capacities (tanδ of up to 0.47), thus they overcome the characteristic brittleness of ceramics.
This cuttlebone-like hierarchical structuring is promising for the fabrication of other technologically relevant materials that combine high porosity with excellent mechanical properties.
1. Knöller, A., Runčevski, T., Dinnebier, R. E., Bill, J. & Burghard, Z. Cuttlebone-like V2O5 Nanofibre Scaffolds – Advances in Structuring Cellular Solids. Sci. Rep. 7, 42951 (2017).