Gellan gum-based ionic conductive hydrogels for flexible sensors and bioelectronics: A review

Gellan gum (GG) is an ion-responsive polysaccharide increasingly investigated for conductive hydrogels used in flexible sensing and bioelectronic applications. This review examines the relationships among GG molecular structure, ion-mediated gelation, hydration, network architecture, charge transport, mechanical response, sensing performance, and operational reliability. Integrating GG with polyacrylamide, poly(vinyl alcohol), conductive polymers, carbon-based materials, ionic salts, and engineered solvent phases has improved conductivity, stretchability, toughness, self-healing, antifreezing behavior, and environmental stability. Representative systems have reported a maximum gauge factor of 31.51 over a 0–900% strain range. At the same time, an antifreezing GG-based network retained a conductivity of 2.2 S m⁻¹ and a gauge factor of 7.4 at −20°C. However, these values arise from different formulations and testing conditions and should not be compared as direct performance rankings. Recent studies also demonstrate piezoresistive, piezoionic, ionic thermoelectric, multimodal sensing, and conductive three-dimensional printing. Major limitations remain in long-term cyclic durability, water retention, electrode–hydrogel interface stability, physiological compatibility, reproducible manufacturing, sustainability assessment, and application-level validation. Progress toward practical use requires standardized characterization, controlled environmental testing, reproducible formulation, interface engineering, scalable processing, and application-specific reliability assessment.