Toward Ideal Biointerfacing Electronics Using Organic Electrochemical Transistors

The biointerface between biological tissues and electronic devices serves as a medium for matter transport, signal transmission, and energy conversion. However, significant disparities in properties, such as mechanical modulus and water content, between tissues and electronics, present a key challenge in bioelectronics, leading to biointerface mismatches that severely impact their performance and long-term stability. Organic electrochemical transistors (OECTs), fabricated with soft, hydrophilic organic semiconductors, offer unique advantages, including low operating voltage, high transconductance, and compatibility with aqueous environments. These attributes position OECTs as promising candidates for ideal biointerfaces. As neural probes, OECTs have demonstrated superior biocompatibility and signal detection capabilities compared to conventional metal electrodes and inorganic semiconductors. Despite these advantages, the applications of OECT as biointerfaces remain constrained by several limitations, including limited performance, poor stability, mismatches among p-type, n-type, and ambipolar semiconductors, relatively high Young’s modulus, and unsatisfactory biointerfacial properties.

In this Account, we summarize our group’s efforts to improve both the electronic and biointerfacial properties of OECTs, encompassing structure–property relationship studies, device optimization/fabrication, and biointerface enhancement. To elucidate the structure–property relationship, we explored the material design strategies and device optimization approaches for high-performance OECTs, highlighting the critical role of doped state properties in the OECT system. Recognizing the unique characteristics of OECTs, we designed hydrophilic polymer backbones to replace conventional neutral ones. These hydrophilic ionic backbones foster strong intermolecular interactions, resulting in improved operational stability. Additionally, we demonstrate that constructing high-spin polymers enables the development of high-performance, balanced ambipolar materials. Based on these materials innovations, we advanced fabrication methods of OECT-based logic circuits and fiber-based OECTs, realizing complementary and ambipolar logic circuits, as well as wearable fabric-based biosensors. Finally, we integrated the exceptional biointerface properties of hydrogels with organic semiconductors, pioneering semiconducting hydrogels that exhibit outstanding mechanical, electrical, and biointerfacial properties. These materials enable efficient in vivo amplification of electrophysiological signals. The concept and realization of semiconducting hydrogels redefine the scope of OECTs and hydrogel electronics, providing a novel approach to ideal biointerfaces. We hope that the perspectives shared in this Account will inspire the development of next generation bioelectronic devices with enhanced biointerface compatibility and expanded functionalities.