Modelling of Sensing Performance of Electrostrictive Capacitive Sensors
Electrostriction is the quadratic coupling between the strain developed in a material and the electric field applied, while piezoelectricity is a linear coupling mechanism existing in a material without center of symmetry. Electrostrictive capacitive sensors have many advantages over vacuum or air gap capacitive sensors. Electrostrictive materials show reproducible, non-hysteric and tunable strain response. Electrostrictive dielectric material sandwiched between two electrodes in a capacitive sensor plays a very important role in performance of the sensor. The dielectric material to be selected is required to possess good electromechanical properties like high strain, high permittivity, good breakdown strength etc.
Standard equations are available for calculation of electrically induced strain in dielectric material and researchers have simplified the standard equation for calculation of electrically induced strain in dielectric material of the sensor. Simplification of equations for six different materials has been analyzed. In case of one simplified equation, error has been found in the range of underestimation from 96% to 3273% and in case of other equation, range of error is from underestimation of 36% to overestimation of 1842%. These errors occur because researchers have neglected many parameters like edge effect, contribution from lateral stress etc., while simplifying these equations.
Electrostrictive dielectric materials have good electromechanical properties for various applications including sensors, but to further enhance properties like permittivity, tensile strength etc. of the dielectric material used in the sensor, nano fillers are incorporated into the dielectric material. In this work, study has been done on two filler materials, TiO2 and ZnO and it is found that the increase in permittivity is more in the materials filled with TiO2 in comparison to ZnO filled materials for same level of filler concentration.
Keywordselectrostrictive capacitive sensor dielectric material strain permittivity
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