Piezoresistive behaviour of flexible PEDOT:PSS based sensors

In this work we developed a low cost flexible polymeric sensor. This sensor is realized using electrochemical synthesis of a conductive polymer (PEDOT:PSS) thin film deposited on a flexible substrate of polyimide using a peeling technique. The sensor was characterized using two different setups able to evaluate the effects of microscopic and macroscopic deformation. Different ranges are considered to correctly define the behaviour and fields of application of the device, and to compare the performances with the data typically available in literature for strain sensors. Using the micro-bending setup we extracted a gauge factor of 17.8 +/- 4, which is well above the typical value for commercially available flexible metallic strain gauges on polyimide substrates. A specific setup is also presented to analyze the behaviour of the sensor with respect to macroscopic bending. We evaluated the change of the resistance of the sample varying the bending angle in the range of 0-60 degrees both in the inward and in the outward direction. We demonstrated in both cases a linear dependence of the resistance with respect to the bending angle, and furthermore a high reproducibility with low hysteresis. Finally we evaluated in the macroscopic regime of deformation also the response time of the sensor obtaining a very good dynamic response with amplitude fluctuations less than few percent with respect to a periodic deformation. (C) 2009 Elsevier B.V. All rights reserved.