A new type of polymer that displays chemoresponsive mechanic adaptability, meaning the polymer can change from hard to soft plastic and vice versa in seconds when exposed to liquid. A radically new approach has been unveiled for developing polymer nanocomposites which alter their mechanical properties when exposed to certain chemical stimuli. The new polymers can be engineered to change their mechanical properties, particularly in stiffness and strength, in a programmed fashion when exposed to a specific chemical. In their new approach, the team used a biomimetic approach -- or mimicking biology -- copying nature's design found in the skin of sea cucumbers.
Marine biologists have shown in earlier studies that the switching effect in the biological tissue is derived from a distinct nanocomposite structure in which highly rigid collagen nanofibers are embedded in a soft connective tissue. The stiffness is mediated by specific chemicals that are secreted by the animal's nervous system and which control the interactions among the collagen nanofibers. When connected, the nanofibers form a reinforcing network which increases the overall stiffness of the material considerably, when compared to the disconnected (soft) state. Building on their recent success on the fabrication of artificial polymer nanocomposites containing rigid cellulose nanofibers, the team mimicked the architecture nature 'designed' for the sea cucumbers and created artificial materials that display similar mechanical morphing characteristics.
This ground-breaking work has been carried out by an interdisciplinary team of researchers from the departments of macromolecular science and engineering and biomedical engineering at the Case School of Engineering and the Louis Stokes Cleveland Department of Veterans Affairs Medical Center.