Enhancing dielectric and piezoelectric properties of micro-ZnO/PDMS composite-based dielectrophoresis

This work aims to enhance the dielectric and piezoelectric properties of polydimethylsiloxane (PDMS) polymer filled with zinc oxide (ZnO) powders. Both ZnO nanoparticles and microparticles are used to prepare piezoelectric composites and a comparison of their dielectric responses is carried out. The experimental results reveal that a higher particle concentration gives rise to the increased dielectric permittivity of composites, especially when particles are aligned in the poling-direction-based dielectrophoretic process. Hence, the microparticles are chosen instead of the nano ones because the microscale facilitates the fabrication process of the composite, especially with high filler content. It also makes it possible to clearly record the movement of particles under alternating (AC) voltage application using optical microscopy. Significant improvement in the dielectric and piezoelectric behavior of the proposed composite has been successfully achieved via dielectrophoretic alignment of ZnO microparticles. This technique leads to increased connectivity between ZnO/ZnO interfaces, allowing for the creation of continuous aligned piezoelectric particles inside the polymer matrix. As a result, the piezoelectric effect is considerably boosted. Finally, the dielectric constant, as well as the charge coefficient of the ZnO particles, is estimated through theoretical approaches for composites containing particles arranged in chains or randomly dispersed. The model predictions are in good agreement with the experimental results. Furthermore, a finite element model (FEM) is developed using Comsol Multiphysics to evaluate these parameters in a 3D structure, which is then compared to those obtained by the above 2D-analytic models.