“In this age of smartphones and tablet computers, touch-sensitive surfaces are everywhere. They’re also brittle, as people with cracked phone screens everywhere can attest. Covering a robot — or an airplane or a bridge — with sensors will require a technology that is both flexible and cost-effective to manufacture in bulk. A team of researchers at MIT’s Computer Science and Artificial Intelligence Laboratory thinks that 3-D printing could be the answer. In an attempt to demonstrate the feasibility of flexible, printable electronics that combine sensors and processing circuitry and can act on their environments, the researchers have designed and built a device that responds to mechanical stresses by changing the color of a spot on its surface. The device was inspired by the golden tortoise beetle, or “goldbug,” an insect whose exterior usually appears golden but turns reddish orange if the insect is poked or prodded — that is, mechanically stressed.”