Hydrogels are soft–wet materials with a hydrophilic three-dimensional network structure offering controllable stretchability, conductivity, and biocompatibility. However, traditional conductive hydrogels only operate in mild environments and exhibit poor environmental tolerance due to their high water content and hydrophilic network, which result in undesirable swelling, susceptibility to freezing at sub-zero temperatures, and structural dehydration through evaporation. The application range of conductive hydrogels is significantly restricted by these limitations. Therefore, developing environmentally tolerant conductive hydrogels (ETCHs) is crucial to increasing the application scope of these materials. In this review, we summarize recent strategies for designing multifunctional conductive hydrogels that possess anti-freezing, anti-drying, and anti-swelling properties. Furthermore, we briefly introduce some of the applications of ETCHs, including wearable sensors, bioelectrodes, soft robots, and wound dressings. The current development status of different types of ETCHs and their limitations are analyzed to further discuss future research directions and development prospects.

Conventional conductive hydrogels are susceptible to swelling in aquatic environments; which compromises their mechanical integrity; a limitation that poses a potential challenge to their long-term stability and application. In this study, a zwitterionic ion-conductive hydrogel was fabricated from polyvinyl alcohol (PVA), acrylic acid (AA), and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SMBA), forming a dual-network structure. A copolymer of zwitterionic SBMA and AA formed the first network, and PVA formed the second network by repeated freeze–thawing. The equilibrium state of zwitterionic SBMA was modulated by AA to protonate the SBMA, which resulted in the conversion of -SO₃⁻ to -SO₃H; thus, hydrogels had the anti-swelling property driven by electrostatic repulsion. In addition, the prepared hydrogels possessed excellent mechanical properties (tensile strength of 0.76 MPa, elongation at break of 322%, and compressive strength of 0.97 MPa at 75% compressive strain) and remarkable anti-swelling properties (80% swelling after 120 h of immersion). Owing to the zwitterionic nature of SBMA, the hydrogel also showed inherent antimicrobial properties and high electrical conductivity, which could be capable of monitoring human movement and physiological signals. This work provides a facile strategy for designing hydrogels with remarkable mechanical properties and anti-swelling characteristics, expanding the application environment of hydrogels in flexible sensing

The development of high-performance sensing materials is critical for advancing bioelectronics. Conductive hydrogels, with their unique flexibility, are promising candidates for biomedical sensors. However, traditional conductive hydrogels often suffer from excessive swelling and undesirable antibacterial activity, limiting their practical use. To overcome these challenges, anti-swelling, antibacterial, and ionically conductive hydrogels were built through free radical polymerization. The preparation was conducted using a monomer mixture comprising acrylic acid (AA), the antibacterial zwitterionic compound [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), and the hydrophobic monomer lauryl methacrylate (LMA). The protonation of SBMA by AA enables electrostatic repulsion, thereby imparting anti-swelling properties to the hydrogel. The introduction of hydrophobic LMA components further enhances the anti-swelling and mechanical performance of hydrogel. The resulting hydrogel exhibits excellent anti-swelling property with a swelling ratio of 59.36% after 120 h and good mechanical performance with a tensile strength of 158 kPa, an elongation at break of 176%, and a compressive strength of 0.37 MPa at 80% strain. In addition, hydrogels possess superior sensing performance for strain sensing with a gauge factor of 1.315 within 40–60% of strain, 330 ms of response time, and 177 ms of recovery time. Furthermore, the hydrogel is capable of monitoring human motion and physiological signals. These attributes make it highly suitable for wearable sensors and biomedical monitoring applications.