Self‐Healing Hydrogels

TLDR

Hydrogels with tunable properties and rapid autonomous self‑healing are sought for soft robotics and tissue engineering, yet most designs trade mechanical robustness for healing speed. This review aims to advance mechanically robust hydrogels that self‑heal autonomously within seconds. The authors survey current strategies, testing protocols, and underlying mechanisms that enable rapid, mechanically resilient self‑healing in hydrogels. They find that faster self‑healing correlates with higher overall healing efficiency, and propose guidelines for future design, highlighting applications in 3D/4D printing, soft robotics, and assisted health technologies.

Abstract

Over the past few years, there has been a great deal of interest in the development of hydrogel materials with tunable structural, mechanical, and rheological properties, which exhibit rapid and autonomous self-healing and self-recovery for utilization in a broad range of applications, from soft robotics to tissue engineering. However, self-healing hydrogels generally either possess mechanically robust or rapid self-healing properties but not both. Hence, the development of a mechanically robust hydrogel material with autonomous self-healing on the time scale of seconds is yet to be fully realized. Here, the current advances in the development of autonomous self-healing hydrogels are reviewed. Specifically, methods to test self-healing efficiencies and recoveries, mechanisms of autonomous self-healing, and mechanically robust hydrogels are presented. The trends indicate that hydrogels that self-heal better also achieve self-healing faster, as compared to gels that only partially self-heal. Recommendations to guide future development of self-healing hydrogels are offered and the potential relevance of self-healing hydrogels to the exciting research areas of 3D/4D printing, soft robotics, and assisted health technologies is highlighted.