US Patent 7180649 Electrochromic-nanoparticle displays

A display comprises spaced first and second electrodes, and a plurality of electrochromic nanoparticles disposed between the electrodes, each of the nanoparticles having an electron-rich state and an electron-depleted state, the two states differing in at least one optical characteristic. Upon injection of charge from one of the electrodes, the nanoparticles switch between their electron-rich and electron-depleted states, thus changing an optical characteristic of the display.