  The piezoelectric nanomaterial ZnO exhibits an excellent piezoelectric
response that can transduce mechanical energy into electrical signals by
applying pressure. The piezoelectric behavior of ZnO nanostructures (especially
nanorods or microrods) is getting considerable attention in the fabrications of
piezo tactile sensors, energy harvesting devices, and other self-powering
implantable devices. Especially vertically aligned ZnO nanorods are of high
interest due to their higher value of piezoelectric coefficient along the
z-direction. In this report, various geometries and alignments of ZnO nanorods
are explored and their effect on strength of piezoelectric output potential has
been simulated by COMSOL Multiphysics software. Best suited geometry and
inclination are explored in this simulation to achieve high piezoelectric
output in haptic and energy harvester devices. The simulation results show out
of many geometries and inclinations the highest piezoelectric output is
demonstrated by the inclined ZnO nanorods due to the application of higher
torque force or shear stress in similar applied force. The high torque force or
shear stress at 60 degree orientation and optimized contributions from all the
piezoelectric coefficients resulted in a high piezoelectric output potential
close to 215 mV which is much higher than the vertically aligned ZnO nanorod
which is approximately 25 mV. The results are contrary to the accepted
understanding that the vertical ZnO nanorods should produce the highest output
voltage due to the high piezoelectric coefficient along the z-axis.
