GlowPaint glow-in-the-dark paint company, 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.
The Litrospheres™ are not affected by heat or cold, and are 5,000-pound crush resistant. They can be injection molded or added to paint. The fill rate of Litroenergy micro particles in plastic injection molding material or paint is about 20%. The constant light gives off no U.V. rays, and can be designed to emit almost any color of light desired.