Introducing Interface Redox Processes in Faradaic Floating Gate Organic Electrochemical Sensors to Improve Sensor Function in Complex Environments
Songyan Yu, Jonathan Harris, Erin L. Ratcliff
Abstract
Organic electrochemical transistors (OECTs) have attracted significant interest in cutting-edge sensing and bioelectronics. One fundamental approach to amplify signals and improve the performance of the OECT sensing is the use of redox reactions at gate electrodes and/or polymer channels. Faradaic processes increase the electric field drop at the semiconductor channel, which can promote an increased transconductance. However, many biological analytes, including peptides and proteins, are not redox-active and are not immediately amenable to Faradaic OECT biosensing. Herein, we establish a set of systematic redox interface modifications to floating gate (FG) OECTs to enable significantly greater transduction at lower operating voltages over capacitive gating in FG architectures. The proof-of-concept device platform consists of (1) a second FG that operates using mixed monolayers of redox-active species and a selective binding probe and (2) a solid-state OECT element with a redox mediator in an ion gel as the electrolyte to align the energy level for efficient doping and amplification. As a point of validation, a Faradaic electrochemical immunoassay for neuropeptide Y (NPY) is used; the NPY immunoassay is composed of ternary monolayers of redox labels and biorecognition elements, with a 439 pM detection of NPY in artificial sweat. Overall, we successfully demonstrate a power-saving Faradaic FG OECT device in the solid state, which is compatible with easy miniaturization and suitable for printable/wearable sensors and bioelectronics for various applications, from point-of-care diagnostics to healthcare.