Ways forward with conductive hydrogels: Classifications, properties, and applications in flexible electronic and energy gadgets

In recent years, conductive hydrogels have garnered significant attention for use in flexible wearable electronics, owing to their exceptional flexibility, multifunctionality, and biocompatibility. This paper provides a comprehensive review of the advancements in multifunctional conductive hydrogels tailored for flexible wearable applications. The review begins with a discussion on the classification of conductive hydrogels, encompassing single-network and dual-network hydrogels based on conductive polymers or conductive additives. Following this, a detailed exploration of conductive hydrogels with multiple functionalities is presented, including toughness, adhesion, self-healing capabilities, swelling resistance, and shape memory, etc. The paper then delves into the application of these hydrogels in flexible devices, such as strain sensors, temperature sensors, triboelectric nanogenerators, energy storage devices, touch panels and bioelectronic devices. Current challenges facing the development and use of hydrogels are also summarized including multifunctional integration and commercialization. Furthermore, conductive hydrogels with targeted property should be designed and prepared according to the requirement of true applications scenarios and mass industrialization. Lastly, the paper offers an insightful and forward-looking perspective aimed at inspiring future innovations in this promising field.