3D printed high transconductance organic electrochemical transistors on flexible substrates

Solution-processable organic semiconducting materials have been utilized for low-cost disposable flexible electronics applications through additive printing techniques. Organic electrochemical transistors (OECTs) are powerful devices for biosensing due to their simplicity, stability in aqueous media and high transconductance. Here, we report fully 3D printed functional OECTs using fused deposition modelling (FDM) and direct writing 3D printing techniques using PEDOT:PSS as the channel material with silver as the source/drain material. These devices demonstrate high transconductance of 12.1 ± 0.4 mS, low operating voltage and high current ON/OFF ratio. They have a threshold voltage in the range of 0.66 ± 0.01  V. These printed OECTs demonstrate good stability and robust behavior after several measurement cycles. We demonstrate pH and K+ ion sensing using these printed OECTs with high sensitivity of −26.4  mV/pH and 240 mV/decade (higher than the Nernst limit of 59.2 mV/decade). These devices can be utilized for biosensing and logic circuitry for different wearable and standalone sensing applications.