RGO-PD Nano-Composite Based Films for Strain Measurement Using Screen Printing Technique

In this paper we are reporting, a strain sensor fabricated by screen printing method using a novel Reduced Graphene Oxide (RGO) and Palladium (Pd) nano-composite on a stainless steel substrate. Pd was chosen due to its higher strain sensitivity compared to other metal composites and screen printing method was adopted because of low cost and easy fabrication. A specified amount of Pd filler was mixed with RGO to enhance its functional and mechanical properties under strain application. As-synthesized nano-composite was characterized by Field Emission-Scanning Electron Microscope (FE-SEM) and X-ray diffraction (XRD) for its surface morphology and crystallinity of the composite. The change in electrical resistance of as-fabricated strain sensor was observed when a mechanical strain was applied on it and its strain sensitivity (Gauge factor) was estimated by cantilever bending method. The Gauge factor as high as 15 was observed for as-prepared strain sensor. The presently developed high sensitive strain gauges are useful to measure force, stress/strain, pressure and displacements in the fields of aerospace, civil engineering, automobile and transport.

I. Introduction

Strain sensors are the most commonly used devices to measure local deformation and fatigue studies, characterization of structures and accurate measurement, indication and recording of force, pressure and displacements etc. The strain sensors electrical resistance changes in proportion to the amount of applied strain. The change in resistance in nickel, iron and copper with elongation was reported by Thomson first in 1856 [1]. Since then, the different types of strain gauges have been widely fabricated with metals and semiconductors. The relation between change in electrical resistance and applied strain is expressed in terms of Gauge Factor (GF). The strain sensitivity (GF) depends upon both the geometric term and fractional change in electrical resistivity . It is expressed as , where ϑ is the Poisson's ratio. The Poisson's ratio in case of metals varies from 0.2 to 0.42. Hence the GF for any metal normally is in the range of 1.4 to 2.1 [2]. The normalized change in resistivity for any metals with applied strain is negligible, whereas in case of semiconductors, it varies from 50 to 100 times than the geometric term [3]. But semiconductor strain gauges with nonlinear behavior are expensive, fragile and mostly suitable for very low strains.