Organic electrochemical transistors as impedance biosensors
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esearch Letters
Organic electrochemical transistors as impedance biosensors Gregório C. Faria†, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305; São Carlos Physics Institute, University of São Paulo, PO Box: 369, 13560-970 São Carlos, SP, Brazil Duc T. Duong† and Alberto Salleo*, Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 Christos A. Polyzoidis and Stergios Logothetidis, Department of Physics, Lab of “Thin Films- Nanosystems & Nanometrology (LFTN), Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece Jonathan Rivnay, Roisin Owens, and George G. Malliaras, Department of Bioelectronics, École Nationale Supérieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France Address all correspondence to Alberto Salleo at [email protected] (Received 12 August 2014; accepted 21 November 2014)
Abstract Interfacing organic electrochemical transistors (OECTs) with biological systems holds considerable promise for building-sensitive biosensors and diagnostic tools. We present a simple model that describes the performance of biosensors in which an OECT is integrated with a biological barrier layer. Using experimentally derived parameters we explore the limits of sensitivity and find that it is dependent on the resistance of the barrier layer. This work provides guidelines on how to optimize biosensors in which OECTs transduce changes in the impedance of biological layers, including lipid bilayer membranes and confluent cell layers.
Introduction Organic electrochemical transistors (OECTs) based on conducting polymers have undergone significant progress in recent years and are poised to become the device of choice for fabricating biosensors using semiconducting polymers.[1–3] Owing to their ability to support both efficient ionic and electronic transport, OECTs are able to transduce biological signals, which typically involve ion flux, into electrical signals with high gain. In a typical OECT, the active material is first processed into a thin film from solution, from vapor phase, or by electrochemical deposition, onto pre-patterned source and drain electrodes. The device is then placed in contact with an electrolyte solution containing a gate electrode. During operation, application of a gate voltage induces ion exchange between the polymer and the electrolyte, which is compensated by hole injection/extraction from the source and drain electrodes. This changes the doping state of the channel, leading to a change in the source–drain current.[4–6] Because the electrolyte swells the polymer and allows ionic species to penetrate the bulk film, OECT devices typically exhibit an enhanced capacitance compared with field effect devices, and therefore display among the highest transconductance values in published literature.[3,7] Additionally the source–drain current is highly † These authors contributed equally to this work. * This author was an editor of this journal during the review and decision stage. For the MRC policy on review and
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