Organogel assisted salting out for strong and anti-fatigue hydrogels as wearable strain sensors

Hydrogels have been rapidly developed recently owing to their excellent flexibility and biocompatibility and exhibit promising applications in biomaterials, flexible electronics, etc. However, when compared to the biological materials, many hydrogels with similarly high water contents display relatively low mechanical properties and it is difficult to achieve a balance between strength, toughness and fatigue resistance simultaneously. Herein, a facile solvent exchange assisted Hofmeister effect strategy is proposed to prepare strong and fatigue-resistant hydrogels with widely tunable water content. The polymer solution is first transformed to an organogel by exchange of the good solvent (dimethyl sulfoxide) to a poor solvent (alcohol), and then the organogel converts to hydrogel after the second step exchange of the alcohol to a saline solution. The alcohol induced gelation assisted salting-out promote the conformation adjustment of macromolecular chain, which endow the hydrogels with excellent comprehensive mechanical properties, with the extraordinary high strength of 26.4 ± 1.6 MPa, superior stretchability of 1252.3 ± 116 %, ultra-high fracture energy of 139.45 ± 37.3 KJ/m², large fatigue threshold of 1837.9 ± 63.4 J/m² (water content of 20.2 wt%) as well as ionic conductivity of 0.34 S/m. Therefore, this work put forward a viable design method to fabricate outstanding performance soft materials for applications in load-bearing material and strain sensor fields.