Development of ferroelectric nanocomposite for capacitive pressure sensors.

Abstract

The demand of flexible electronic devices led the scientific community to develop novel electroactive materials for various sensing devices to realize them in the potential applications in health monitoring, robotics, electronic skin and diagnostics. Especially, monitoring the human activities using integrated sensors are dedicated to non/invasive measurements such as pressure and force are seen in dielectric and piezoelectric applications. Currently, capacitive sensors with various dielectric materials with high sensitivity are realized as low power electronics devices in prosthetics, humanoids, structural health monitoring, biomedical and planter pressure monitoring in neurogenerative pathology applications. Materials for the capacitive sensors generally consist of electroactive polymers and ceramics as dielectric layer. Polymers which are flexible, robust are widely used and have low dielectric properties. On the other hand, ceramic having high dielectric properties are restricted its widespread usage due to brittle/rigid in nature. Currently, polymer nanocomposite with synergetic properties of polymer matrix and ceramic fillers are realized for capacitive pressure sensors. The present work is intended to develop a polymer-ZnO based nanocomposite and to fabricate a flexible capacitive pressure sensor. Zinc oxide nanostructures modified with graphene greatly influenced the crystallinity and showed strong interaction with polyvinyldine fluoride matrix. Frequency dependent dielectric studies suggests the PVDF-ZnO-Gr nanocomposite shows the higher permittivity (~30 at 100 Hz) than PVDF-ZnO (~20 at 100Hz) nanocomposite. The electromechanical performance was investigated by measuring the change in capacitance response under various load conditions. The capacitive pressure sensing response is considerably higher than that of the pristine PVDF-based device. The significant change in capacitance upon load is observed by the induced electrical potential due to displacement of electrodes and change in spacing between the fillers in the polymer matrix.