Processing, microstructure, and electrical properties of PMMA/ZnO nanocomposite films for prospective energy-conversion applications

PMMA/ZnO polymer–ceramic nanocomposite films were fabricated by dispersing zinc oxide (ZnO) nanoparticles up to 10 wt.% into the polymethylmethacrylate (PMMA) using ultrasonic probe sonication and subsequent solution casting. Impedance measurements were performed to determine the frequency-dependent dielectric constant and electrical conductivity of the nanocomposites. Mechanical-to-electrical energy-conversion characteristics of the composites were evaluated by measuring the current and voltage produced under cyclic mechanical loading. The dielectric constant ( \({\upvarepsilon }_{{\text{r}}}\) ${\mathrm{\epsilon }}_{\text{r}}$ ) was found to increase with increasing ZnO content at a frequency of 20 Hz. However, the values of \({\upvarepsilon }_{{\text{r}}}\) ${\mathrm{\epsilon }}_{\text{r}}$ decreased monotonically as the frequency increased from 20 to 200 Hz. The dielectric constant of nanocomposites varied from 4.7 for PMMA to 6.9 for 10-wt.% ZnO nanocomposite at 20 Hz. The conductivity of nanocomposites varied from \(5.2 nS{m}^{-1}\) $5.2nS{m}^{-1}$ to 7.6 \(nS{m}^{-1}\) $nS{m}^{-1}$ in the same range. The maximum average current and voltage output of 10 wt.% ZnO nanocomposites were found to be ~ 24 nA and ~ 4 V, respectively, under the mechanical force of  \(2.58\pm 0.01\) $2.58\pm 0.01$  N. These results are critical in determining processing–structure–electrical property correlations in PMMA/ZnO nanocomposite films and exhibit the potential for self-powered micro-devices.