SAN DIEGO - The accidental discovery of a silicon form of "gunpowder" is pointing the way toward integrating nanoscale explosives onto silicon chips, a technology that might provide microelectromechanical systems (MEMS) with a means for rocket propulsion. Chemists at the University of California, San Diego, had a chip blow up in their faces after scratching a porous silicon wafer that had been impregnated with gadolinium nitrate. The formula is now being proposed as a means to create self-destruct mechanisms, on-chip retro rockets or fingernail-size chemical analyzers. "It's about the equivalent-size explosion you would get from a couple of caps in ...