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\subsection{Piezoelectric Nanogenerators}  Piezoelectric generators have become a hot topic in recent years due to their ability to capture electric energy through movement. Irregular human movement, such as walking, expels energy that otherwise would be lost. GaN nanowires demonstrate piezoelectric effects when they are mechanically strained by an outside force, generating a charge across the nanowire. At the same time, they are both flexible and strong, with Young's modulus ranging from 60 - 120 GPa observed in diameters from 90 - 180 nm. This charge can be captured and utilized for powering various devices. \cite{Dai_2015}  In 2014, Wang’s group managed to characterize the piezoelectric properties of a single nanowire device by bending it under a transmission electron microscope and observing the potential differences between two leads connected to either ends of the wire. They concluded that an optimized single nanowire device had better piezoelectric properties as its carrier concentration decreased. \cite{Wang_2014} The creation of piezoelectric device that consists of a first electrode with GaN nanowires separated by an organic piezoelectric material connected to a second electrode. The nanowires are a n-type semiconductor compared to the p-type semiconductor of the organic layer. The entire device is mechanically flexible, which allows for electricity to be generator when pressure is applied. The device sometimes has a built-in DC converter to store the captured energy. \cite{choi2014}