Drug delivery by means of micro robots, also called microbots, which are no bigger than a human cell may one day allow drugs to be delivered exactly where needed in the body. The nickel-coated cage-like device, 100 microns long and 40 wide, is small enough to be injected into the body and guided wirelessly with an electromagnetic field. To enable wireless control, parts of the microbot are coated with a thin layer of nickel which is ferro-magnetic.