A Systematic Theoretical, Simulation and Experimental Approach to Distinguishing Triboelectric and Piezoelectric Outputs in Combined Tribopiezoelectric Generators

Zinc oxide (ZnO) nanorod (NR) arrays have been widely applied in the fabrication of piezoelectric generators (PEG) to harvest waste mechanical energy since 2006 [1]. A triboelectric generator (TEG) was firstly reported [2] in 2012 during the application of the PEG. Since then, many devices have been developed to make use of both the triboelectric and piezoelectric effects (combined tribopiezoelectric generators, or TPEG) in order to improve the output potential. Though the working mechanism of each transduction effect is well understood, systematic investigations are rarely made into which transduction mode generates which aspects of the output when testing the combined-effect devices.
In this paper, the development of a multiphysics simulation of a TPEG device is described whereby known theory of both triboelectric and piezoelectric effects is proposed as a method to allow systematic assignment of features of the output to the transduction mechanism through which they are generated. The simulation is capable of calculating separately the potentials due to the triboelectric and piezoelectric effects at all times during the device’s operation, a feat which is experimentally impractical. The accuracy of each of the two physical models included is confirmed by initial validation of the simulations against a pure triboelectric device and a pure piezoelectric device. The simulations are then shown to accurately predict the output of a TPEG, additionally demonstrating which aspects of the experimental results are due to the triboelectric effect and which are due to the piezoelectric effect, thereby demonstrating the efficacy of the simulation.