Damageless Tough Hydrogels with On-demand Self-reinforcement

TL;DR

This paper introduces a damageless reinforcement method for tough hydrogels using strain-induced crystallization, enabling high toughness and instant energy recovery, suitable for artificial tissues.

Contribution

It presents a novel SIC-based reinforcement strategy that allows hydrogels to self-reinforce on demand without damage, improving cyclic durability.

Findings

Achieved toughness of 5.5 - 25.2 MJ/m$^3$

87% - 95% instant energy recovery between cycles

SIC occurs at crack tips, redirecting crack growth

Abstract

Most tough hydrogels are reinforced by introducing sacrificial structures that can dissipate input energy. However, since the sacrificial damages cannot recover instantly, the toughness of these gels drops substantially during consecutive cyclic loadings. Here, we propose a new damageless reinforcement strategy for hydrogels utilizing strain-induced crystallization (SIC). In Slide-Ring (SR) gels with freely movable cross-links, crystalline repetitively forms and destructs with elongation and relaxation, resulting in both excellent toughness of 5.5 - 25.2 MJ/m$^3$ and 87% - 95% instant recovery of extension energy between two consecutive 11-fold loading-unloading cycles. Moreover, SIC occurs "on-demandly" at the crack-tip area where strain amplification and stress concentration take place and forces the crack to turn sideways. The instantly reversible tough hydrogels are promising candidates for applications in artificial connective tissues such as tendon and ligament.