As consumers, we want our electronic gadgets to be durable. But as patients, we might want them to dissolve — inside our bodies. Scientists reported Thursday that they succeeded in creating tiny medical devices sealed in silk cocoons that did the work they were designed for, then dissolved in the bodies of lab mice. It's an early step in a technology that may hold promise, not only for medicine, but also for disposal of electronic waste.In the experiment, the devices were designed to generate heat, a potential strategy for fighting infection after surgery by killing germs, said John Rogers of the University of Illinois at Urbana-Champaign, an author of the study.