A Printed Biosensor Based on an Organic Electrochemical Transistor with Mediated Gate Electrode

Biosensor technology is an expanding field of research and there is a great market demand for low-cost disposable sensors. The aim of this project was to come up with a printed, disposable biosensor for glucose based on an organic electrochemical transistor (OECT). The organic semiconductor PEDOT:PSS was used as the material for the transistor channel and the gate electrode was made of carbon bulk modified with the different redox mediators potassium ferricyanide and ferrocene and the catalyst cobalt phthalo cyanine (CoPC) respectively. The enzyme glucose oxidase, that oxidases glucose, was used as sensing element and was immobilised on top of the gate electrodes. The sensor was fabricated with screen-printing, a low-cost technique that offers high throughput and is robust, simple and flexible. The gate electrodes were evaluated with cyclic voltammetry and chronoamperometry before integrated in the transistor device. The results showed that electrodes containing CoPC could detect hydrogen peroxide, a product in the reaction between glucose and the enzyme. Ferricyanide-electrodes showed good results regarding the activity of the mediator but no good results were achieved for the ferrocene-mediated electrodes. Transistor devices with CoPCmediated electrodes gave a response for 1mM hydrogen peroxide at 0.55V with good reproducibility, but the sensitivity needs to be further investigated. Transistor measurements with ferricyanide-mediated gates at 0.25V and glucose oxidase indicated that the glucose sensing works with these electrodes as well, but more measurements are needed. It was also concluded that the geometry of the transistor device had an influence on the relative response for the sensor, and a long channel proved to be better than a wide. The method used to fabricate the sensor offers great variation options and few production steps and the mediator approach enables inexpensive material costs