MIT researchers have developed a battery-free, self-powered sensor that can harvest energy from its environment. Because it requires no battery that must be recharged or replaced, and because it requires no special wiring, such a sensor could be embedded in a hard-to-reach place, like inside the inner workings of a ship’s engine. There, it could automatically gather data on the machine’s power consumption and operations for long periods of time. The researchers built a temperature-sensing device...