An apparatus includes a switch comprising microelectromechanical elements, the microelectromechanical elements including a sealed chamber containing a dielectric element, and conductors in the sealed chamber. The conductors are arranged such that application of greater than a predetermined voltage to at least one of the conductors causes ionization breakdown of the dielectric element to provide an electrically conductive path between the conductors. In another implementation, a switch includes a nanotube electron emitter or a radioactive isotope electron emitter.