Replacing a Battery by a Nanogenerator with 20 V Output

Replacing batteries by nanogenerators (NGs) in small consumer electronics is one of the goals in the emerging fi eld of self-powered nanotechnology. It is shown that the maximum measured output voltage of an NG optimized with pretreatments on the as-grown ZnO nanowire fi lms reaches 20 V and the output current exceeds 6 mu A, which corresponds to a power density of 0.2 W cm(-3). The NG is also demonstrated to replace a battery for driving a electronic watch.