Electropolymerization of Organic Mixed Ionic-Electronic Conductors: Fundamentals and Applications in Bioelectronics

Conducting polymers, particularly those capable of transporting both ionic and electronic charges─commonly referred to as organic mixed ionic-electronic conductors (OMIECs)─have played a transformative role in enabling bidirectional communication between biological systems and electronic circuits. This ability has driven the field of bioelectronics to expand in three distinct directions: biointerfacing, sensing, and neuromorphic computing. Biointerfacing and sensing allow for the extraction of interpretable chemical and electrochemical signals from living organisms, while neuromorphic computing, in addition to efficiently processing complex signals, can translate electronic signals into the frequency domain that the nervous system uses to communicate. In the bioelectronics context, OMIECs have been untethered from previous requirements of high charge mobility, fast switching times, and long-range crystallinity, which makes electropolymerization a more attractive route to fabricate OMIECs on bioelectronic devices. This review examines the fundamental principles, practical aspects, and prominent applications of OMIEC materials fabricated by electropolymerization.