Organic Electrochemical Transistors for Oxygen Sensing in Water with Battery Free, Near Field Communication Readout

Organic Electrochemical Transistors (OECTs) are investigated as electrochemical sensors due to their amplification behaviour, stability in aqueous environments and compatibility with low-cost processing on flexible plastic substrates. For widespread, sustainable application in sensor-networks, OECTs must be compatible with wireless, battery free sensor readout schemes. Although OECTs operate at low-voltages, high transistor channel currents and long response time-constants make the integration with low-power electronics difficult. To address the issue, we investigate hydrogel based OECTs for oxygen sensing in liquid and gas and their power consumption. To achieve stable, interference-free O2 sensors with miniaturized OECTs we introduce a silicone based O2 permeable membrane. Our results show how the membrane enables fast and stable sensor readout in micrometric OECTs and reduces power consumption to be compatible with a commercial battery-free NFC chip readout. We also demonstrate stable O2 sensor operation in complex mixtures with several competing redox analytes. Our result opens the opportunity for developing bio-compatible, non-invasive and wireless OECTs sensors for wound healing monitoring or environmental monitoring.