Fully Passive Electrochemical Oxygen Sensor Enabled With Organic Electrochemical Transistor

Abstract

Wireless and battery-free sensor operation is essential for sustainable sensor networks for environmental and health monitoring. Achieving such a fully passive design in electrochemical sensors is challenging due to the need for amplification and control electronics as realized in potentiostats. To address this issue, organic electrochemical transistors (OECTs) are introduced as amplified sensors and demonstrate an OECT-based oxygen sensor that exploits the electrochemical reduction of oxygen, akin to the Clark electrode. To build the sensor, the transistor thin film fabrication protocol is integrated with the deposition of a gas permeable silicone membrane and a hydrogel electrolyte. To assess the sensor's power consumption, a model that links power consumption to the OECT geometry and the material properties of the semiconducting channel is established. This model identifies the optimized OECT design that is compatible with commercial near-field communication (NFC) microcontrollers. In the optimized design, the interrogating NFC radio signal is sufficient to power the microcontroller, achieve sensor readout, and transmit the digitized sensor current, enabling oxygen monitoring in air or water without wired connections or batteries. These findings provide a first example and quantitative argumentation on exploiting OECTs in low-power electrochemical sensor architectures.