Self-healing in Glasses with a Little Push

If glasses are liquids, they can flow. If they can flow, mechanical fractures can repair spontaneously over time, formally enabling self-healing in glassy materials. Besides increasing the temperature, mechanical deformations are another way to circumvent the small hiccup of age-of-the-universe-long relaxation times. Previous work has shown that shear deformations can accelerate the molecular mobility of glass-forming liquids, and further anneal glasses down their energy landscape.

Based on these ideas and using molecular dynamics simulations, we show that segmental mobility in deeply quenched glasses is accelerated by oscillatory shear deformations, a result that strongly depends on different regimes of deformation amplitudes related to the local or global breaking of molecular cages. We use this principle to induce healing of mechanical fractures in a regime of oscillatory deformations which maintains the bulk system below the glass transition and enhances the mobility around the crack, where surface effects speed up the segmental dynamics.