Bioceramics as Impact-Resistant Biotools and Elastic Energy Storage Devices: Lessons from the Mantis Shrimp Dactyl Club

Reference	Presenter	Authors (Institution)	Abstract
03-047	Ali Miserez	Miserez, A.(Nanyang Technological University);	Mantis shrimps are predatory marine crustaceans that use an ultra-fast biomineralized hammer called “the dactyl club” to shatter the hard shells of their preys. Two elements of the dactyl structure have drawn interest for bioinspired ceramics: the impact-resistant hammer as well as the saddle-shape spring, in which a high density of elastic energy is stored and released during the swift strikes of the club. The multi-scale structural design imparting these bioceramics with their unique mechanical characteristics will be presented. The club is made of an outer impact layer and an inner softer region. Crystalline fluorapatite is the dominant phase near the impact surface, whereas amorphous calcium phosphate is more abundant near the interface with the inner region, which is itself less mineralized and comprised of partially mineralized chitin fibers assembling into a helicoidal structure. Contact mechanics studies have shown that this microstructural design leads to distinct mechanical responses: quasi-plasticity with high compressive yield strength in the outer layer and strain-hardening in the inner layer, which combine to endow the club with a high impact tolerance. The saddle spring is a bi-layer structure built from a multi-phase biocomposite at the micro-scale with distinct organic/inorganic ratios within each layer. The outer layer, subjected to compressive stresses is heavily mineralized, whereas the inner layer sustaining tensile stresses contains a higher of content biopolymeric building blocks. This design allows optimum storage of elastic energy while at the same time impeding brittle failure. The saddle thus exhibits both stiffness and extensibility at the macroscopic level thereby overcoming the inherent limitation of ceramics. References 1. Weaver, J. C. et al. Science 336, 1275-1280, (2012). 2. Amini, S. et al. Nat. Comms 5:3187, (2014). 3. Amini, S, et al. Nat. Materials 14, 943–950, (2015). 4. Tadayon, M. et al. Adv. Func. Mat. 25, 6437–6447, (2015).
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