Sterilizable vertical n-type organic electrochemical transistors for skin-conformal ECG monitoring

The development of stable, high-performance epidermal biosignal monitoring devices is critical for advancing wearable healthcare technologies. Here, we present a novel electrochemical transistor-based biosignal sensor utilizing a 4-terminal vertical Corbino configuration and an n-doped poly(benzodifurandione) (n-PBDF) polymer. The 4-terminal device configuration effectively reduces the parasitic resistance, enabling a high transconductance of 374 mS at a low operational voltage, and one of the highest reported μC* values of 1787 F cm⁻¹ V⁻¹ s⁻¹ for n-type OECTs. In addition, this device achieves exceptional operational stability, maintaining consistent performance over extended periods, and demonstrates a superior shelf-life stability under ambient conditions. Furthermore, the sensor exhibits robust sterilization capabilities, withstanding both UV and thermal sterilization processes without performance degradation. Mechanical flexibility, a key requirement for on-skin applications, is ensured by the intrinsic properties of the n-PBDF polymer and the ultra-thin device architecture. The combination of these features makes this device an ideal candidate for monitoring of biosignals such as electrocardiograms, addressing practical challenges in wearable biosensing technologies.