Georgia Tech inventors have developed a transparent and flexible NG (TFNG) using a ZnO nanowire (NW) array on a polydimethylsiloxane (PDMS) substrate. The fully packaged NG has  transparency, flexibility, and robustness. It is able to harvest energy under a rolling vehicle tire with stable output. Thus, it can be used as a self-powered dynamic sensor to detect vehicle speed and weight, which can be used to monitor transportation flow.

First, the transparent and flexible PDMS substrate is prepared in the ideal thickness. Closely packed ZnO NWs are uniformly grown on the PDMS to form the core component of the 1.5 cm ´ 1 cm TFNG. The NWs are then coated with a polymer for insulation. Finally, transparent electrodes are deposited on the top and bottom surfaces. The transmittance of the PDMS film is over 80%, and that of the fully packaged device is 50–60% (with potential for significant improvement) in the visible range. An output power density of ~5.3 mW cm^-3 can be achieved, which is sufficient to power small electronic devices. No significant decay in output voltage was observed during continuous use (1 hr, ~500 cycles).