Proving that batteries have a little juice left in them yet, researchers at Rice University have built a rechargeable battery inside a single nanowire that’s 150nm (0.15 micron) in diameter. The researchers haven’t built just one, either: they’ve created an entire centimeter-scale array of thousands of nanowire batteries. Each nanowire is a completely discrete battery, consisting of all the usual elements: anode, cathode, and electrolyte.The best way to understand how a nanowire battery works is to look at the image below, and then read the following words. They started with a layer of copper (the golden layer at the bottom). Using electrodeposition (electroplating) nickel/tin anodes are “grown” from the bottom copper plate, and then drop-coated with a polymer gel (polyethylene oxide) that both acts as an insulator between the nanowires and as the electrolyte. A second polymer (polyaniline) is then drop-coated to create the cathode, and a layer of aluminium is placed on top to complete the circuit. All in all the entire battery is about 50 microns tall; the width of a human hair, and almost invisible side-on.
