Design principles for π-conjugated hydrogel semiconductors

Hydrogels are widely used in biomedical and bioelectronic applications owing to their tissue-like properties, including biocompatibility, softness and three-dimensional architecture. In recent years, semiconducting behaviour was demonstrated in hydrogels through the network design of π-conjugated polymers, extending their potential to advanced electronic applications such as transistors. In this Review, we provide an overview of the design, fabrication, characterization and benchmarking standards of π-conjugated hydrogel semiconductors, a rapidly evolving field requiring interdisciplinary knowledge across organic electronics, electrochemistry and soft materials. We demonstrate how to understand and regulate ion and electron transport, as well as their interactions, both thermodynamically and kinetically, in these π-conjugated supramolecular systems. Finally, we envision the potential of these materials to advance spatiotemporal biological research, wearable healthcare, implantable medicine and beyond.