Bio-inspired mechanically adaptive nanocomposites

Inspired by the skin of sea cucumbers, a novel class of polymers which can change their mechanical properties on command has been developed.

This program focuses on the design of polymers which change their mechanical properties on command. These materials morph upon exposure to a pre-defined stimulus in a highly selective and reversible manner and are attractive for many technologically relevant applications. The structure and function of the materials under investigation mimic the skin of sea cucumbers. These creatures have the ability to alter the stiffness of their skin when threatened. This adaptive mechanical behavior is achieved through a nanocomposite architecture, in which stiff collagen fibers reinforce a soft matrix. The stiffness of the tissue is regulated by controlling the interactions, and thereby the stress transfer, among adjacent collagen fibrils. We introduced many examples of water-responsive polymer nanocomposites, which mimic this architecture and whose morphing mechanical characteristics are similar to those of the biological model. Our artificial materials comprise rigid cellulose nanocrystals (CNCs), which can form hydrogen-bonded load-bearing networks in a given matrix. Upon modest swelling with water the interactions among the CNCs are disrupted due to competitive hydrogen bonding to water, concomitant with a dramatic stiffness reduction. We are currently adapting the framework to nanocomposites in which the CNCs are decorated with motifs that impart responsiveness to non-chemical stimuli.

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254