Vertical Organic Electrochemical Transistors and Electronics for Low Amplitude Micro‐Organ Signals

Abstract

Electrical signals are fundamental to key biological events such as brain activity, heartbeat, or vital hormone secretion. Their capture and analysis provide insight into cell or organ physiology and a number of bioelectronic medical devices aim to improve signal acquisition. Organic electrochemical transistors (OECT) have proven their capacity to capture neuronal and cardiac signals with high fidelity and amplification. Vertical PEDOT:PSS-based OECTs (vOECTs) further enhance signal amplification and device density but have not been characterized in biological applications. An electronic board with individually tuneable transistor biases overcomes fabrication induced heterogeneity in device metrics and allows quantitative biological experiments. Careful exploration of vOECT electric parameters defines voltage biases compatible with reliable transistor function in biological experiments and provides useful maximal transconductance values without influencing cellular signal generation or propagation. This permits successful application in monitoring micro-organs of prime importance in diabetes, the endocrine pancreatic islets, which are known for their far smaller signal amplitudes as compared to neurons or heart cells. Moreover, vOECTs capture their single-cell action potentials and multicellular slow potentials reflecting micro-organ organizations as well as their modulation by the physiological stimulator glucose. This opens the possibility to use OECTs in new biomedical fields well beyond their classical applications.

Vertical organic electrochemical transistors for complementary circuits

“…Previously reported pioneering organic transistor architectures with vertical source-drain arrangements functioned as OECTs only when using permeable (for example, Ag nanowires) electrodes 22,26,33 , or when operated as electrical double-layer transistors or field-effect transistors. Therefore, bulk ion penetration and redox reactions are not involved, and only a small semiconductor volume under the top contact functions as the charge-carrying channel [34][35][36][37][38] . In contrast, the present approach uses simple thermal evaporation of dense and thick (150 nm) Au electrodes through a shadow mask, in combination with a photopatternable semiconductor layer, to create a structure with excellent ion intercalation.…”

Soft Fiber Electronics Based on Semiconducting Polymer

“…Rapidly reversible doping and dedoping transitions present whole new application scenarios. OECTs have proven their ability to capture neuronal signals with high fidelity and amplification, and have recently been used to capture electrical signals during islet secretion, which are substantially smaller than action potentials. , Fiber-shaped OECT devices have been described above. In conclusion, OECT-based probe arrays may be potential candidates for next-generation BCI applications.…”

Towards organic electronics that learn at the body-machine interface: A materials journey

“…[7] As a result, over the past few years, biointerfaces based on miniaturized transistors has enabled the direct acquisition and amplification of signals while improving signal-to-noise ratio. [21,22] Among them, electrolyte-gated transistors (EGTs) have emerged as powerful tools in bioelectronics due to their stability in aqueous environments, low-voltage operation, and ability to both transduce and amplify biological signals into electronic signals by directly interfacing with the biological environment under study (e.g., blood, saliva, tears, cells, skin) as illustrated in Fig. 1.…”

“…Mostly, ionic current is the limiting current rather than the electronic current in terms of device speed, however, depending on the target application, organic semiconductors have shown to successfully match the speed of biological signals. [21,22] Another crucial metric for OECTs at the bio-interface is the device stability which can be quantified as: (1) operational stability (which is the ratio of initial and final value of the performance of interest, normally measured after 10 4 cycles for OECTs) and (2) environmental…”