Initiation of cracks and other types of damage on microscopic level is a critical problem in polymers during their service in structural applications and has been shown to change thermal, electrical, and acoustical properties, and eventually leading to whole scale failure of the material. Therefore, early sensing, diagnosis and repair of microcracks become necessary for removing the latent perils. In this context, the materials possessing self-healing function are ideal for long-term operation. Self-repairing polymers are based on the concept of human body's natural response to damage and its ability to recover with minimal external help.
The advances in this field show that selection and optimization of proper repair mechanisms are prerequisites for high healing efficiency. It is a challenging job to either invent new polymers with inherent crack repair capability (intrinsic self-healing) or integrate existing materials with novel healing system (extrinsic self-healing). Comparatively, extrinsic self-healing techniques might be easier for large-scale usage for the moment. The works and outcomes in this aspect have broadened the application possibility of polymeric materials. Also, the extended service life of components made from these intelligent materials would contribute to reduce waste disposal. It is undoubtedly important for building up a sustainable society.