Ionic polymers for bioelectronics

In the last decades, ionic polymers have been used as key materials for energy applications as solid polymer electrolytes, binders and ionomers in devices such as batteries, electrolyzers and fuel cells. More recently, ionic polymers are becoming enabling materials also in bioelectronics for new biomedical technologies. This review aims to collect and discuss the recent advances in polymer design, synthesis and characterization of ionic polymers for bioelectronic devices. The review includes the ionic polymer families that are being developed, such as poly(ionic liquid)s and poly(eutectic solvents), as well as ionic gel families such as hydrogels, ionogels and eutectogels. Polymers and gels from purely ionic conductors to mixed ionic electronic conducting polymers will be discussed. We delve into structure-ion conductivity relationships and outline current and possible applications of such novel conductive materials. These ionic polymers are central to the development of fundamental bioelectronic devices such as organic electrochemical transistors, amperometric detectors, controlled-release devices, and even disruptive neuromorphic computing.