Biofunctional Interfaces: The Role of Hydrogels in Organic Transistors

Over the past four decades, organic electronics has progressed from a specialized domain within polymer physics into a highly interdisciplinary research field, with organic electrochemical transistors (OECTs) and organic field-effect transistors (OFETs) at its forefront. However, the widespread adoption of these devices in bioelectronics and wearable technologies has been hindered by the inherent rigidity, hydrophobicity, and limited biocompatibility of conventional interfacial materials. Hydrogels, three-dimensional hydrophilic polymer networks, offer a promising alternative, combining ionic conductivity, tissue-like mechanical softness, and excellent biocompatibility. This review systematically outlines recent advances in hydrogel-based organic electronics, encompassing the classification and essential characteristics of natural, synthetic, and hybrid hydrogels. It further elaborates on their roles in OECTs (as electrolytes and active channels) and OFETs (such as low-voltage gate dielectrics), clarifies operational mechanisms and performance enhancement strategies, and addresses key challenges, including dehydration and interfacial adhesion. Finally, the review prospects future applications in wearable bioelectronics and neuromorphic computing, aiming to serve as a foundational reference for cross-disciplinary studies.