Fiber-based organic electrochemical transistor

#The present invention relates to an electrochemical device, and particularly but not exclusively, to an electrochemical transistor device based on conducting organic materials.

#The transistor is an important building block of electronic devices and has been widely used in the development of various sensors, including electrical and chemical sensors. Among the different types of transistor based sensors, electrochemical transistors (ECTs) have gained particular attentions for their simple and low-cost fabrication, mechanical flexibility and also the adaptability to miniaturization, in contrast to the traditional transistors such as field effect transistors (FETs). Organic materials such as conducting polymers have been used to develop organic electrochemical transistors (OECTs), which facilitate the use of OECTs in the biological and chemical sensing areas.

#In contrast to field effect transistors (FETs), in which the detecting mechanism is field driven, i.e., the density of charge carriers between the source and the drain terminals are modulated via capacitive coupling between the gate electrode and the transistor channel, the detecting mechanism of the organic electrochemical transistors (OECTs) is potential driven, i.e., based on electrochemical redox reactions between an electrolyte and the organic electrodes. The switching between an oxidized state and a reduced state during the electrochemical reaction corresponds to a change of conductivity of the transistor, and thereby facilitating the quantification of the analyte in the electrolyte. The operation of the OECTs in electrolytes enables the OECTs to be operable under relatively lower voltages, and thus allows the OECTs to be tailored to specialized applications such as for detection of biological molecules in the physiological environment.

#FIG. 1 is a schematic sectional view showing the organic electrochemical transistor (OECT) as embodied in the present invention;

#FIG. 2 is a schematic longitudinal section showing the layers of a first part of the OECT of FIG. 1 that includes the source and drain contacts;

#FIG. 3A is a longitudinal section showing the layers of a second part or gate electrode of the OECT of FIG. 1, without the surface of the gate electrode being functionalized;

#The following description is given by way of example only to illustrate embodiments of the invention. The terminology used is for illustrative purpose only, and is not intended to limit the scope or use of the invention, unless the text clearly and explicitly requires otherwise.

#Referring to FIG. 1, the organic electrochemical transistor (OECT) 10 of the present invention includes two elongate parts formed on respective lengths of fiber 28, 48: a drain/source assembly 20, comprising axially spaced apart source and drain contacts 22, 24, and a gate electrode assembly 40 comprising a gate electrode 42. In use, the drain/source assembly 20 and gate electrode assembly 40 are placed in an electrolyte 100 and electrically connected via an external circuit 60.

#A monofilament fiber 28, 48, such as a nylon fiber, forms the substrate upon which both the drain/source assembly 20 and the gate electrode assembly 40 are built up in circumferential layers, using a layer-by-layer fabrication technique. The fibers 28, 48 can be of a diameter of, for example, 0.3 mm to 0.5 mm, but it should be understood that the invention is not limited to the use of fibers of these dimensions or material. A first layer of electrically conductive material is applied directly to the fibers 28, 48 to form the source contact 22, the drain contact 24, and the gate electrode 42.