Fully Passive Electrochemical Oxygen Sensor Enabled With Organic Electrochemical Transistor

Wireless and battery-free sensor operation is essential for sustainable sensornetworks for environmental and health monitoring. Achieving such a fullypassive design in electrochemical sensors is challenging due to the need for am-plification and control electronics as realized in potentiostats. To address thisissue, organic electrochemical transistors (OECTs) are introduced as amplifiedsensors and demonstrate an OECT-based oxygen sensor that exploits the elec-trochemical reduction of oxygen, akin to the Clark electrode. To build the sensor,the transistor thin film fabrication protocol is integrated with the deposition ofa gas permeable silicone membrane and a hydrogel electrolyte. To assess thesensor’s power consumption, a model that links power consumption to theOECT geometry and the material properties of the semiconducting channelis established. This model identifies the optimized OECT design that is com-patible with commercial near-field communication (NFC) microcontrollers. Inthe optimized design, the interrogating NFC radio signal is sufficient to powerthe microcontroller, achieve sensor readout, and transmit the digitized sensorcurrent, enabling oxygen monitoring in air or water without wired connectionsor batteries. These findings provide a first example and quantitative argumen-tation on exploiting OECTs in low-power electrochemical sensor architectures.