Silkworm cocoons shipped by the boxful from Japan to an optics lab at Tufts University will meet a different fate from those headed to textile factories around the world. Rather than being woven into curtains or clothing, the strong protein fibers that caterpillars once spun around themselves will be used to build optical materials that can serve as the basis for sensors and other devices. Bioengineer Fiorenzo Omenetto, who creates the devices, ultimately hopes to build implantable, biodegradable sensors that could help monitor patients' progress after surgery or track chronic diseases such as diabetes.

Omenetto realized that silk was good for more than shirts and ties, he says, when he got to talking with David Kaplan, the head of Tufts's biomedical-engineering department, with whom he shares a hallway. Kaplan turns silk proteins into cell-friendly scaffolds for engineering biological tissues, including corneal implants. The strongest natural fiber known, silk is favored by tissue engineers because it's mechanically tough but degrades harmlessly inside the body.