We have developed a nanogenerator that is driven by mechanical forces to produce continuous direct-current output. The nanogenerator was fabricated with titanium dioxide nanoparticle arrays that were placed beneath a conducting electrode with a small gap. The force drives the electrode up and down to bend and/or vibrate the nanoparticles. A piezoelectric process converts mechanical energy into electricity. The electrode collects the output electricity from all of the nanoparticles. The approach presents an adaptable, mobile, and cost-effective technology for powering nanodevices by harvesting mechanical energy from the environment