From dopamine sensing to electrochromic actuation: an analog logic OECT-based platform

The current bioelectronic horizon is formed of various architectures that aim to mimic biological structures and provide precise detection for a wide range of molecules. However, chemical signals in similar devices are transduced only as electrical outputs, with the lack of a chemical response. To address this issue, we investigated the role of Organic Electrochemical Transistors (OECTs) in providing electrochemical actuation and observed the influence of parameters on the potential output. The analog control system is driven by dopamine sensing, that is obtained through the analyte oxidation by applying a potential over +0.2 V at the gate electrode.1 As dopamine is oxidized, the released electrons can migrate towards the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) channel, that is consequently reduced. The fixed current Id at the channel allows for a resistance increase in the material, thus providing a modulation in the voltage Vd measured at the drain. Electrochemical reactions rely on variations of electrochemical potential and the need for a different reference arises, as in traditional OECT-based systems the source electrode also operates as reference. Therefore, we implemented a Saturated Calomel Electrode (SCE), that opposes the drain in an open circuit potential measurement, to characterize the drain electrochemical potential variations. Dopamine concentration in the system was correlated with drain voltage Vd and drain electrochemical potential Ed, while parameters as the gate voltages and the fixed Id values were explored to observe their influence on the potential modulation. The results were exploited to induce a dopamine-driven electrochromic actuation, with a Prussian Blue-Indium Tin Oxide (PB-ITO) electrode. By connecting the drain electrode to the electrochromic PB actuator, the dopamine-driven system was enabled. Due to PEDOT reduction, the electrochromic actuator responds with a reduction of PB to Prussian White, visibly confirmed by the coloration change from blue to transparent. The system described represents the first step towards an analog intelligent system, that allows both sensing and actuation in a single device.2 1. Gualandi, I., Tonelli, D., Mariani, F. et al. Selective detection of dopamine with an all PEDOT:PSS Organic Electrochemical Transistor. Sci Rep 6, 35419 (2016). 2. D’Altri, G., et al. Dopamine-mediated analog control of electrochromic reactions through organic electrochemical transistor, Small Sci., 6, e202500635 (2026).