Bio-inspired mechanically adaptive materials through vibration-induced crosslinking.

In nature, bone adapts to mechanical forces it experiences, strengthening itself to match the conditions placed upon it. Here we report a composite material that adapts to the mechanical environment it experiences—varying its modulus as a function of force, time and the frequency of mechanical agitation. Adaptation in the material is managed by mechanically responsive ZnO, which controls a crosslinking reaction between a thiol and an alkene within a polymer composite gel, resulting in a mechanically driven ×66 increase in modulus. As the amount of chemical energy is a function of the mechanical energy input, the material senses and adapts its modulus along the distribution of stress, resembling the bone remodelling behaviour that materials can adapt accordingly to the loading location. Such material design might find use in a wide range of applications, from adhesives to materials that interface with biological systems. A polymer gel composite self-strengthens in response to mechanical vibrations due to activation of mechanically sensitive ZnO crosslinking agents in its matrix, in a process that resembles bone remodelling observed in animals.