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Electrolyte‐gated organic transistors (EGOTs) leveraging organic semiconductors' electronic and ionic transport characteristics are the key enablers for many biosensing and bioelectronic applications that can selectively sense, record, and monitor different biological and biochemical processes at the nanoscale and translate them into macroscopic electrical signals. Understanding such transduction mechanisms requires multiscale characterization tools to comprehensively probe local electrical properties and link them with device behavior across various bias points. Here, an automated scanning dielectric microscopy toolbox is demonstrated that performs operando in‐liquid scanning dielectric microscopy measurements on functional EGOTs and carries out extensive data analysis to unravel the evolution of local electrical properties in minute detail. This paper emphasizes critical experimental considerations permitting standardized, accurate, and reproducible data acquisition. The developed approach is validated with EGOTs based on blends of organic small molecule semiconductor and insulating polymer that work as accumulation‐mode field‐effect transistors. Furthermore, the degradation of local electrical characteristics at high gate voltages is probed, which is apparently driven by the destruction of local crystalline order due to undesirable electrochemical swelling of the organic semiconducting material near the source electrode edge. The developed approach paves the way for systematic probing of EGOT‐based technologies for targeted optimization and fundamental understanding. [ABSTRACT FROM AUTHOR]

Probing nanoscale electrical properties of organic semiconducting materials at the interface with an electrolyte solution under externally applied voltages is key in the field of organic bioelectronics. It is demonstrated that the conductivity and interfacial capacitance of the active channel of an electrolyte‐gated organic field‐effect transistor (EGOFET) under operation can be probed at the nanoscale using scanning dielectric microscopy in force detection mode in liquid environment. Local electrostatic force versus gate voltage transfer characteristics are obtained on the device and correlated with the global current–voltage transfer characteristics of the EGOFET. Nanoscale maps of the conductivity of the semiconducting channel show the dependence of the channel conductivity on the gate voltage and its variation along the channel due to the space charge limited conduction. The maps reveal very small electrical heterogeneities, which correspond to local interfacial capacitance variations due to an ultrathin non‐uniform insulating layer resulting from a phase separation in the organic semiconducting blend. Present results offer insights into the transduction mechanism at the organic semiconductor/electrolyte interfaces at scales down to ≈100 nm, which can bring substantial optimization of organic electronic devices for bioelectronic applications such as electrical recording on excitable cells or label‐free biosensing. [ABSTRACT FROM AUTHOR]

Organic electronic materials offer an untapped potential for novel tools for low-invasive electrophysiological recording and stimulation devices. Such materials combine semiconducting properties with tailored surface chemistry, elastic mechanical properties and chemical stability in water. In this work, we investigate solution processed Electrolyte Gated Organic Field Effect Transistors (EGOFETs) based on a small molecule semiconductor. We demonstrate that EGOFETs based on a blend of soluble organic semiconductor 2,8-Difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) combined with an insulating polymer show excellent sensitivity and long-term recording under electrophysiological applications. Our devices can stably record the extracellular potential of human pluripotent stem cell derived cardiomyocyte cells (hPSCs-CMs) for several weeks. In addition, cytotoxicity tests of pharmaceutical drugs, such as Norepinephrine and Verapamil was achieved with excellent sensitivity. This work demonstrates that organic transistors based on organic blends are excellent bioelectronics transducer for extracellular electrical recording of excitable cells and tissues thus providing a valid alternative to electrochemical transistors. Image 1 [ABSTRACT FROM AUTHOR]