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Carbon black/silicone rubber composite is a desirable material for highly flexible strain sensors due to its repeatable piezoresistive characteristics, low cost, and simple fabrication process. By customising the conductivity and elastic modulus of the composite, the material can easily be adapted for many human physiological sensing applications. For applications such weight distribution sensors for wheelchair users, it is desirable to have not just a single sensor reading but instead a 2D map of pressure or strain. In this work, after demonstrating that the material can be modelled to give estimated strain value, we have developed a system to give a 2D map of pressure applied to the sensor using Electrical Impedance Tomography (EIT). This method has the advantage that a 2D pressure map can be obtained from a sensor using a homogeneous cast sheet of composite with electrodes around the perimeter only, without requiring complex patterning or a sensor array. Although the design is scalable, our demonstration system was fabricated using a 100 mm diameter pressure pad of carbon black (CB) silicone composite with electrodes evenly spaced around its perimeter. A low-cost circuit was developed to apply current to the material and measure the voltage between electrodes. The voltage measurements were then reconstructed into maps of resistivity and indications of compressive stress. Testing demonstrates that the fabricated pressure sensor can sense localised pressure within the pressure pad. The positional accuracy of the sensor was found to be on average 3.6 mm for the 100 mm diameter circular domain under test.
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