Suk-Won Hwang of the University of Illinois at Urbana-Champaign and several colleagues made circuits out of silkworm cocoons, superthin sheets of porous silicon, and electrodes made of magnesium. All these materials are biocompatible and because they're extremely thin and soluble, they dissolve even in minute quantities of water. The silk is the main structural scaffold, and it determines the dissolution rate of the entire device. Biomedical engineer Fiorenzo Omenetto at Tufts University, a coauthor, figured out how to adjust the silk protein's properties so it degrades at a wide range of intervals. The silk is dissolved and then re-crystallized, and by controlling the crystallization, the researchers can control the rate at which it dissolves again.