The vertically integrated nanogenerator (VING) is one of the most used designs in mechanical energy harvesting using piezoelectric nanowires, due to its easiest manufacturing process. Here, a new modeling approach is presented in order to reduce the computation time of a whole VING finite element simulation. In this work, the effect of the polymer layer (Parylene C), in which nanowires are immersed, on the electromechanical behavior of the whole VING is taken into account. The active part of the VING (nanowires-polymer composite) is considered as a 1-3 piezocomposite. It is formed with ZnO piezoelectric nanowires; however, this study can be applied to any type of piezoelectric nanowires (PZT, GaN, PVDF, etc.) and matrix materials (PDMS, PMMA, Al 2 O 3 , etc.). The present method relies on the finite element method applied to a single nanowire-composite cell in open-circuit condition, combined with an analytical modeling of the full VING. This approach allows the computation time to be drastically reduced without inducing significant approximation errors. The expected maximum power, internal capacitance, and optimum resistance can be deduced thanks to this efficient modeling tool, offering wide perspectives for the optimization of such VING devices.

The effect of Young's modulus and dielectric permittivity of the polymer matrix in vertically integrated nanogenerators (VING) on their output performance is studied by combining the finite element method and analytical modeling. To conduct this study, an elementary cell is considered, based on one ZnO nanowire (NW) surrounded by the polymer matrix. It is demonstrated that the polymer matrix should have the lowest Young's modulus and permittivity as possible, in order to maximize the output voltage and power. Four different materials, which have already been proposed in literature for such composite VING, are then compared: Parylene C, poly(methyl methacrylate), Al2O3, and poly(dimethylsiloxane) (PDMS). Simulation results show that PDMS, which has the lowest values of both Young's modulus and permittivity, gives the highest output performance. Finally, the sensitivity to another design parameter—the surface density of the NWs—is calculated, and it is shown that choosing a polymer material with the lowest Young's modulus and permittivity is more powerful to improve the VING performance.