1. An actuator, comprising: an unfixed carbon nanotube coupled to a mechanical output; and a control conductor configured to receive an electrical current and situated so that a magnetic field produced by the current in the conductor exerts a magnet force on the unfixed carbon nanotube, wherein the unfixed carbon nanotube is situated between first and second fixed carbon nanotubes that are coupled to receive respective electrical currents, and the control conductor is situated so that the electrical current in the control conductor magnetically urges the unfixed carbon nanotube toward at least one of the first and the second fixed carbon nanotubes.