Piezo-resistive Pressure Sensor Array with Photo-thermally Reduced Graphene Oxide
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Piezo-resistive Pressure Sensor Array with Photo-thermally Reduced Graphene Oxide Rouzbeh Kazemzadeh1 and Woo Soo Kim1 1 School of Mechatronic Systems Engineering, Simon Fraser University, Surrey, B.C. Canada V3T 0A3 ABSTRACT We report a highly sensitive pressure sensor fabricated by photo-thermally reduced Graphene oxide (GO) with silver nano wires (AgNWs). Pressure sensors are fabricated in form of the inter-digitated capacitors (IDC) composed of two finger electrodes with pattern width of 500 µm. The fabricated IDCs are compared to the previously reported MEMS-based pressure sensors' sensitivity. The fabricated sensor is easily attachable on any surface for monitoring applied forces or pressure and maintains excellent electrical conductivity under high mechanical stress and thus holds promise for durable bio-medical sensors. INTRODUCTION Pressure sensors or touch sensors are popular components to detect the changes of forces (per unit area) applying on objects for the applications such as human touch/pressure detection, or touch screen pads. The pressure sensor material needs to have proper electrical properties as well as being transparent and mechanically durable for fore-mentioned applications. Graphene has been used as piezo-resistive sensing materials with really superior electrical and mechanical properties. Considering the unique electro-mechanical properties of Graphene; thin film sensors based on Graphene could be conductive and transparent with acceptable sensitivity. Ease of fabrication and high accuracy for future generation of devices such as sensors, RFIDs, OTFT etc. is of great importance, especially if such devices are flexible and conformable. One such fabrication methods is laser scribing of thin films. This particular method is very suitable for scribing a wide range of materials like polymers, metals, ceramics and glass [1]. Fine features such as patterns for sensors and circuit designs for microelectronics can easily be imprinted [2]. Photo-thermal scribing by laser does not rely on the use of chemicals or high temperatures and shortens the reaction time from several hours to a few minutes or seconds [3]. In addition to manufacturing considerations, the sensor material itself needs to have proper electrical properties as well as being transparent and mechanically durable. Only a few materials meet all of these requirements. Graphene-Metal nanowire hybrid structures as conductive, transparent, and stretchable electrodes allow charge transfer in the hybrid nanostructure, each complementing the disadvantages of the other component. Metal wire network can be Silver nanowires (AgNW). Graphene adsorption at inter-wire junctions can enhance electrical properties by several orders of magnitude [4], [5], [6], [7]. Considering the unique electro-mechanical properties of Graphene; thin film sensors based on Graphene could be conductive and transparent with acceptable sensitivity. Several different methods, like chemically derived Graphene [8] chemical vapor deposition (CVD) [9], [10] epitaxial growth of
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