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.

Strong and tough fibrous hydrogels reinforced by multiscale hierarchical structures with multimechanisms

“…( G ) Fourier transform infrared (FTIR) spectroscopy. Reproduced under Creative Commons Attribution License ( 25 ). Copyright 2022, Wiley-VCH.…”

“…For example, combining unidirectional freeze-casting and salting-out ( 24 ), a single-composition fibrous hydrogel exhibited unique stepwise fracture behavior and crack propagation blocking ability, resulting in superior mechanical properties coupled with high strength and toughness. Furthermore, a number of tough and functional fibrous hydrogels have been fabricated through a combination of freeze-casting with other procedures, such as ion enhancement ( 25 ), solution replacement ( 26 ), and annealing ( 15 , 27 ). A universal design strategy of ice-templating and subsequent thermal annealing has been proposed with impressive enhancement in fiber crystallinity, fracture energy, and fatigue threshold ( 27 ).…”

Low Hysteresis and Fatigue-Resistant Polyvinyl Alcohol/Activated Charcoal Hydrogel Strain Sensor for Long-Term Stable Plant Growth Monitoring

“…The crack growth of the hydrogel is observed after several cycles. The crack propagation of the PVA-AC conductive hydrogel is caused by the destruction of the crystalline domain of the hydrogel [ 36 , 37 ]. The λ max value is finally determined by testing the crack propagation of the hydrogel under different strains.…”

Tough hydrogel with high water content and ordered fibrous structures as an artificial human ligament

“…Their tensile strengths are usually below 1 MPa, and they are prone to fracture. 6,7 Rigid polymer networks are suitable for strong hydrogels, such as polyvinyl alcohol (PVA), alginate, 8 chitin and cellulose. 9 Materials in nature have anisotropic structures across multiple scales.…”