Optimization of Electromechanical Properties of Piezoelectric Nanocomposite Elastomers

Nanocomposite elastomers, including highly flexible strain gauges and foam, have been shown to exhibit a piezo-response, or change in electrical impedance, under mechanical strain. Both classes of sensors are comprised of an elastomer matrix (typically silicone for strain gauges and polyurethane or latex for foam) mixed with conductive nanofillers including nickel-coated carbon fiber and nickel powder. Though these sensors are used for different applications, their piezoresistive responses can be optimized with respect to the same variables. An optimal piezoresponse for each sensor is defined by a maximum range of output resistance registered during strain. Parameters of both nanocomposites that similarly affect their piezo-responses include sensor size (length, width, height) and volume fraction of the conductive filler. Since the relationships between these and the resistance values of interest are similar between both sensors, they are selected to optimize as design variables. The optimal width, thickness, and filler volume fraction for a piezoresistive nanocomposite is found deterministically and accounting for uncertainty. Results show that small sensors with a high volume fraction of conductive fillers yield optimal resistance ranges at a given strain.