Fig. 1: Illustration of an OFET-based biochemical sensor.

a Schematic of the biosensor design for analyte detection in electrolyte solution. The biosensor consists of an OFET transducer and an extended-gate sensing electrode immobilized with probes. V_Ref is the bias voltage at the reference electrode (Ag/AgCl). V_GS is the resulted gate-to-source voltage on the OFET. I_D is the drain current to be measured by the subsequent readout electronic system. b Diagram for potential over a simplified electrochemical cell model with an extended-gate metal as the interfacial material for sensing. The charged molecules captured onto this surface create a potential shift (ΔV_int) at the solution/metal interface and thus equal ΔV_GS seen from the OFET. c Illustration of the transfer-curve shift from the I_D–V_GS curve of the OFET to the I_D–V_Ref curve when the OFET sensor is tested in solution by sweeping V_Ref, and the induced significant output-current change from the background level (∆I_D0) in the subthreshold regime even at a small threshold-voltage shift (∆V_th).