Strong and Tough Conductive Organo-Hydrogels via Freeze-Casting Assisted Solution Substitution

Abstract

High strength, toughness, and conductivity are among the most sought-after properties of flexible electronics. However, existing engineering materials find it difficult to achieve both excellent mechanical properties and high conductivity. To address this challenge, this study proposes a facile yet versatile strategy for preparing super-tough conductive organo-hydrogels via freeze-casting assisted solution substitution (FASS). This FASS strategy enables the formation of organo-hydrogels in one step with exquisite hierarchical anisotropic structures coupled with synergistic strengthening and toughening effects across multiple length scales. As an exemplary material, the prepared polyvinyl alcohol (PVA) organo-hydrogel with solvent content up to 87 wt% exhibits a combination of high strength (6.5 MPa), high stretchability (1710% in strain), ultra-high toughness (58.9 MJ m−3), as well as high ionic conductivity up to 6.5 S m−1 with excellent strain sensitivity. The exceptional combination of mechanical properties and conductivity makes the PVA organo-hydrogel a promising flexible electronics material. In addition, the FASS strategy can also endow hydrogels with multi-functions, including thermo-healability, freezing tolerance and shape recoverability, and can be applied to various hydrogel materials, such as carboxymethyl cellulose, sodium alginate, and chitosan. Hence, this work provides an all-around solution for preparing advanced strong and tough conductive soft materials for a multitude of applications.