“MPK Co., has come up with self-luminous micro particles called Litrospheres™ which they say are inexpensive, non-toxic, and will stay on for 12+ years (half-life point) continuously – without having to be plugged into any power source. It is a betavoltaic technology, using a radioactive gas, whose “soft” emission of electrons from the beta emitting gas cannot penetrate the glass or polymer wall of the microspheres.”