Measuring the Viscoelastic Characteristics of a Single Interface in Bio-composite Materials via Micro-cantilever Vibrations

Biological tissues are naturally complex structural materials which possess various architectural motifs across the nano-to-micro meter length scales – and are mostly characterize with superior mechanical properties. From a bio-inspired perspective, unfolding the novel structural-mechanical principles of these materials may introduce new design strategies for pioneering engineering materials with outstanding functional capabilities. On the material level, biological tissues can be viewed as bio-composites, comprising various reinforcing elements (e.g. platelets, bricks and prisms) that provide them anisotropic mechanical stiffness, along with a binding bio-polymeric matrix phase that provides the bio-materials complementary mechanical capabilities such
as high toughness and energy adsorption by visco-elasticity. The content of the reinforcing elements in some classes of the bio-composite may even reach 90%-95% volume fraction, while the complementary biopolymeric phase is structured as ultra-thin interfaces in between the reinforcing elements. Measuring the native mechanical properties of these bio-polymeric interfaces is currently one of the standing challenges in biomaterial science.

In this talk I will introduce a novel experimental-analytical framework to probe the viscoelastic behavior of an individual interface, extracted from the frequency response of a micro-cantilever - carved from the biocomposite material. The tip-vibrations of the micro-cantilever, that possess a single-interface in a well-defined location, were examined by a nano-dynamic analysis instrumentation (nano-DMA) - from which the effective iscoelasticity characteristics of the compliant interface material was extracted analytically. The method, that provides pioneering indirect measurement capabilities for thin bio-composite interfaces, was employed to characterize the micro-sale organic interfaces of the prismatic layer of the mollusk shell (Pinna nobilis).