Hydrogels for Flexible Electronics

Abstract

Hydrogels have emerged as promising materials for flexible electronics due to their unique properties, such as high water content, softness, and biocompatibility. In this perspective, we provide an overview of the development of hydrogels for flexible electronics, with a focus on three key aspects: mechanical properties, interfacial adhesion, and conductivity. We discuss the principles of designing high-performance hydrogels and present representative examples of their potential applications in the field of flexible electronics for healthcare. Despite significant progress, several challenges remain, including improving the antifatigue capability, enhancing interfacial adhesion, and balancing water content in wet environments. Additionally, we highlight the importance of considering the hydrogel–cell interactions and the dynamic properties of hydrogels in future research. Looking ahead, the future of hydrogels in flexible electronics is promising, with exciting opportunities on the horizon, but continued investment in research and development is necessary to overcome the remaining challenges.

Functionalization of Natural-Derived Biogels for Soft Bioelectronics

“…Diverse combinations of a single pair of the above mechanisms have been innovatively explored for the design of tough biogels . For example, an interpenetrating network structure with two or more independent cross-linked and intertwined polymer networks in the gel matrix has been intensively studied for improving the mechanical properties of gels, because such an interpenetrating structure could implement the energy dissipation through the fracture or reversible cross-linking or domain transformation of sacrificial polymer chains, and maintain high elasticity by the long-chain networks . Considering that a wide selection of natural biopolymers can provide domain transformation or reversible interaction for mechanical energy dissipation, strategies that interpenetrate such biopolymers with other long-chain polymer networks may be efficient to obtain tough biogels.…”

“…Ion-conductive, electron-conductive, and hybrid electron–ion-conductive biogels have been developed for soft bioelectronics . The conductivity of ion-conductive biogels is from freely moving ions that come from electrolytes, polyelectrolytes, or ionic liquids, and relies on the ion transportation in biogel matrix . A well-designed porous structure and high ion concentration is conducive to improving the ion conductivity.…”

Self-Healing and Freeze-Resistant Boat-Fruited Sterculia Seed Polysaccharide/Silk Fiber Hydrogel for Wearable Strain Sensors

“…As the digital healthcare landscape continues to evolve, – wearable strain sensors – have garnered significant interest in the fields of motion monitoring, , health monitoring, , and human–computer interactions. , Their flexibility, , softness, , and adhesion , have made hydrogels a key class of materials for next-generation flexible electronic sensing devices. – For instance, wearable sensors leveraging hydrogel with conductivity based on an amylopectin/poly­(acrylamide–acrylic acid) polymer have been effectively utilized to monitor human movements . Similarly, flexible hydrogels developed from silver nanowires, carbon black nanoparticles, poly­(vinyl alcohol) (PVA) and poly­(acrylamide) exhibit high strain/pressure sensitivities .…”

Liquid metal–hydrogel composites for flexible electronics

“…11–14 However, ion-conducting hydrogels have some inherent disadvantages, including low conductivity, unstable electrochemical properties in physiological environments, and slow response time due to the low ion movement rate. 15 In contrast, compounding conductive fillers into hydrogel matrices can effectively overcome these limitations. The inherent rigidity of commonly used conductive fillers, including carbon nanotubes (CNTs), 16,17 graphene (GO), 18,19 and metal nanoparticles/nanowires, 20,21 leads to poor interfacial compatibility between fillers and hydrogels, which in turn affects the mechanical properties of hydrogel composites.…”