Yesterday it was light-emitting band-aids, and now a Japanese printing company has created light-emitting ink that can be used on clothing. As long as you're also willing to wear a battery or two.
The ink mixes silica nanoparticles, a protective electrolite to prevent evaporation, and a ruthenium compound that, when voltage is applied, lights up. Currently, the ink - which can be screenprinted onto cloth and paper - only manages to glow red, but its creators are working on adding other color choices. Dai Nippon Printing, the company that invented the gel-like ink, hopes to be able to market the process within the next five years.
Press 'print' for a light-emitting T-shirt [New Scientist]