High-Output Nanogenerator by Rational Unipolar Assembly of Conical Nanowires
We present a simple, cost-effective, robust, and scalable approach for fabricating a nanogenerator that gives an output power strong enough to continuously drive a commercial liquid crystal display. Utilizing the conical shape of the as-grown ZnO nanowires, a nanogenerator is fabricated by simply dispersing them onto a ﬂat polymer ﬁlm to form a rational “composite” structure. It is suggested that the geometry induced unipolar assembly of the conical nanowires in such a composite structure results in a macroscopic piezoelectric potential across its thickness by introducing a mechanical deformation, which may be responsible for driving the ﬂow of the inductive charges between the top and bottom electrodes. A compressive strain of 0.11% at a straining rate of 3.67% produces an output voltage up to 2 V (equivalent open circuit voltage of 3.3 V). This is a practical and versatile technology with the potential for powering small size personal electronics.