Interface engineering in organic electrochemical transistors toward multifunctional bioelectronics

Bioelectronics enables bidirectional transduction between biological and electronic signals, with organic electrochemical transistors (OECTs) emerging as a leading platform due to their volumetric doping, high transconductance, low-voltage operation, and compatibility with soft, aqueous environments. While conjugated polymers provide versatile and scalable device architectures, the performance and functionality of OECTs are fundamentally governed by interfacial processes. This review focuses on how the interface engineering-across electrolyte/channel, channel/electrode, and device/tissue interfaces-directly controls ion transport, charge injection, capacitance, and biocompatibility. We summarize recent advances showing that tailored interfacial design enables multifunctional applications, including high-accuracy biosensing, bio-synaptic emulation, and integrated neuromorphic computing. We further outline key strategies for engineering these interfaces to advance next-generation OECT-based bioelectronics, and conclude by discussing remaining challenges and future directions.