Biological stick-slip mechanisms: what impact does this have on materials mechanics and biomimetic design?

Biomimetic design has gained popularity and momentum in recent years as advances in characterisation have allowed scientists and engineers to better comprehend how biological materials function. One area that stands out in view of materials mechanics is the stick-slip mechanism, which can occur at molecular, mesoscopic and macroscopic length scales. As consequence of hierarchical stick-slip mechanisms, biological materials are able to absorb, dissipate and redistribute mechanical energy when loaded or subjected to impaction. As a result, biological materials are able to withstand fracture more effectively than engineering materials. This keynote lecture paper aims to bring to light the combination of stick-slip and structural hierarchy in biology, and the means by which they collectively heighten the energy absorptive capabilities of biological materials. The paper will then draw upon recent advancements in the characterisation of biological materials and will elucidate a new macroscale stick-slip mechanism that we have recently discovered in Haliclona sp. that onsets double strain-hardening behaviour.