Dramatic enhancement in energy harvesting for a narrow range of dimensions in piezoelectric nanostructures

Recent work suggests that flexoelectricity causes significant enhancement of electromechanical coupling of nonuniformly strained piezoelectric and nonpiezoelectric nanostructures below a material-dependent length scale. In the present work, employing an atomistically informed dynamical continuum model that accounts for flexoelectricity, we argue that in a narrow range of geometric dimensions, piezoelectric nanostructures can dramatically enhance energy harvesting. Specifically, in the case of lead zirconate titanate (PZT) material employed in the form of cantilever beams, our results indicate that the total harvested power peak value can increase by 100% around 21 nm beam thickness (under short circuit conditions) and nearly a 200% increase may be achieved for specifically tailored cross-section shapes. The key (hereto undiscovered) insight is that the striking enhancement in energy harvesting is predicted to rapidly diminish (compared to bulk) both below and above a certain nanoscale structural length thus providing a rather stringent condition for the experimentalists.