Ultraflexible Self-Healing Guar Gum-Glycerol Hydrogel with Injectable, Antifreeze, and Strain-Sensitive Properties.

Recently, flexible, injectable, and strain-sensitive hydrogels have attracted great research interest for application as electronic skin and wearable strain sensors. The synergistic integration of high flexibility, rapid self-healing, and antifreezing properties makes injectable, strain-sensitive, and self-healing guar gum hydrogels still a great challenge. Here, inspired by the strong hydrogen bonding of glycerol and water, the chelation cross-linking between glycerol and borax, we constructed a compact three-dimensional dynamic cross-linked net formed of glycerol-water-borax. Under stress, dynamic interactions of glycerol-water-borax net act as sacrificial bond energy for effective dissipation, which enables the hydrogel to achieve high flexibility, stretchability, and injectability. More importantly,because of the presence of glycerol, the antifreeze and moisturizing properties of the gel are improved. The hydrogel also exhibited an ultrafast self-healing ability of only 15 s. In addition, the results show that the hydrogel has self-adhesive properties and strain sensitivity. The hydrogels have the potential to be used to make flexible, wearable, and 3D-printable electronic skin and strain-sensitive sensors.