A multiscale approach to nanocomposite electrical generators

• Presence of an optimum aspect ratio that generates maximum voltage is revealed.
• A minimum diameter for ZnO nanowires is calculated below which the generated electric potential cannot be detected.
• Nonzero electric potential is found at the mid-plane due to the change in sign of shear stresses.
• Multiple advantages are disclosed for nanocomposite electrical generators compared to bended ZnO nanowires such as higher durability due to lack of moving part, more sustainable electric source due to axial electric potential distribution, easy to scale up.
• A general model to calculate the generated current, voltage, and power of a scaled-up nanocomposite electrical generator is also proposed.

A multiscale approach is pursued to develop a modified shear-lag model for capturing size-scale effects on electrostatic potential generated by a zinc oxide (ZnO) nanowire (NW) in a nanocomposite electrical generator (NCEG). The size-scale effect on elastic modulus of ZnO NWs is captured using a core–surface model. Closed form of governing equations is derived considering linear elasticity for axisymmetric problem and cylindrical coordinate system. Two different configurations based on parallel and series connecting of NCEGs for application in NEMS/MEMS devices are also studied. Parametric studies are performed for sample cases to demonstrate application of the developed model. It is shown that aspect ratio and diameter of NWs are crucial controlling parameters for determining the performance of nanocomposite electrical generators. Numerical results disclose that there is an optimum aspect ratio for each NW of specific diameter. It was also shown that despite the symmetry of loading with respect to mid-plane normal to the NW's axis, the electric potential is not symmetric.

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