Figure 4.

(a) Schematic illustration of the breaking and reforming of hydrogen bonding that resulting in high stretchability and desirable self-healing property. Stress-strain behavior of the self-healed PUA film with different healing time at 100 °C. Reprinted with permission from ref. [143], Copyright 2019 Springer Nature. (b) Schematic structure of the amorphous calcium carbonate/ polyacrylic acid/alginate mineral hydrogel based on the dynamic chelation of the Ca²⁺ and carboxylic groups, and the structural design of ionic skin. Photos of the autonomously healed hydrogel sensor and the self-healing hydrogel sensor attached to a bent finger. Reproduced with permission [144]. Copyright 2017, Wiley-VCH. (c) Underwater healing process of highly polar and hydrophobic fluorinated polymers with dynamic dipole-dipole interactions. The photos of completely severed conductor and electrical conductivity recovered immediately when contacted. Reproduced with permission [147]. Copyright 2018, Wiley-VCH.