Flexible Organic Electrolyte Gated FET Biosensor with Integrated Soft Fluidics for Cortisol Monitoring in Oral Samples

Electrolyte Gated Field Effect Transistor (EGFET) devices are ideal biosensor platforms as they require small sample volumes, can directly transduce biomolecule quantities to electrical signals, and have a fast sensor response time, making them a desirable candidate for future integration into a Point of Care (PoC) device. However, the lack of emphasis on EGFET device integration with fluidic sample handling has led to very few architectures that are PoC viable in their present states. In response, we have created the first flexible, organic, electrolyte gated FET (OEGFET) cortisol sensor, with integrated soft fluidic microchannels. Our OEGFET demonstrates excellent cortisol sensing properties, with improved longevity, electrical characteristics, and detection range over previously published OEGFET devices. The device demonstrates robustness to repeated testing and preserved bioactivity over a period of 15 days. The nominal operating voltage is up to 5V, 4x lower than the previously reported device. The broad cortisol sensitivity range of 27.6µM - 2.76pM comprehensively covers the physiological concentration range of cortisol in saliva, with a detection limit 10x lower than our previous device. The integrated device is low temperature and low-cost fabricated onto flexible polymer substrates, tailored as the first such PoC compatible EGFET oral biosensor reported.