Conductive hydrogels for bioelectronics: molecular structures, design principles, and operation mechanisms

Abstract

Bioelectronics have become an emerging research field for their wide application in health monitoring and human–computer interaction. Conductive hydrogels are promising candidates for the fabrication of bioelectronics. In this review, the structural characteristics, design principles, operation mechanisms and advantages of multifunctional conductive hydrogels for bioelectronics are highlighted. First, the representative conductive materials, the general synthetic approaches of conductive hydrogels and the conductive mechanism are introduced, the latter of which comprises electronic conduction and ionic conduction. Then this review focuses on the multifunctional design criteria and operation mechanisms of conductive hydrogels, including mechanical reinforcement, self-healing mechanisms, antibacterial properties and biocompatibility. The chemical reactions and interactions to achieve the self-healing function, like Diels–Alder reaction, Schiff base bonds, dynamic borate ester bonds, ionic and metal-coordination interaction, hydrogen bonding, and host–guest interaction, are clarified clearly. The antibacterial properties of hydrogels such as polymer-based inherent antibacterial hydrogels, inorganic nanoparticle-loaded antibacterial hydrogels, antibiotic-loaded antibacterial hydrogels and stimuli-responsive antibacterial hydrogels are elucidated. Finally, the applications of multifunctional conductive hydrogels in bioelectronics, and challenges and opportunities are discussed. This review provides a deep understanding of the mechanisms and design principles of multifunctional conductive hydrogels, and proposes a new perspective for next-generation hydrogel-based bioelectronics.