A gelatin-based ionic conductor with a dense/loose alternating network enabled by surface active cellulose

Abstract

Although conductive and stretchable ionic conductors are increasingly prepared for flexible sensing applications, such as health monitoring, tissue engineering, and electronic skin, achieving a balance between remarkable mechanical properties and high sensing sensitivity remains a significant challenge. In this work, a dense/loose alternating network was meticulously constructed through a pre-assembly process in sodium citrate solution and a subsequent re-assembly in FeCl3 solution. This approach ensured the robustness of the network structure and facilitated ion migration. Within the network, a gelatin network cross-linked via covalently and hydrogen bonds was significantly enhanced by a synergy of micro-enhancement and dynamic bidirectional crosslinking containing hydrogen bonds, imine bonds, and Fe coordinate bonds enabled by surface active cellulose. Benefiting from the dense network, the obtained composite hydrogels delivered a strong tensile strength (496.3 kPa), outstanding elastic modulus (917.6 kPa), and an excellent energy dissipation rate (55.6 %) at 80 % of strain. The loose polymer network can also endow Fe3+/Cl− ions with sensitive mobility, leading to an ultra-high sensing sensitivity (maximum GF: 20.06). These exceptional properties enable the ionic conductor to accurately detect a wide range of motions and pressures without being affected by environmental noise. With attributes such as reusability, biodegradability, strength, and sensitivity, this ionic conductor emerges as a reliable soft material with promising applications in the field of healthcare monitoring, wearable strain sensor sensors, and writing anti-counterfeiting materials.