  Glassy polymer melts such as the plastics used in pipes, structural
materials, and medical devices are ubiquitous in daily life. They accumulate
damage over time due to their use, which limits their functionalities and
demands periodic replacement. The resulting economic and social burden could be
mitigated by the design of self-healing mechanisms that expand the lifespan of
materials. However, the characteristic low molecular mobility in glassy polymer
melts intrinsically limits the design of self-healing behavior. We demonstrate
through numerical simulations that controlled oscillatory deformations enhance
the local molecular mobility of glassy polymers without compromising their
structural or mechanical stability. We apply this principle to increase the
molecular mobility around the surface of a crack, inducing fracture repair and
recovering the mechanical properties of the pristine material. Our findings
establish a general physical mechanism of self-healing in glasses that may
inspire the design and processing of new glassy materials.
