This stretchy, wearable device lights up an LED using only the warmth of your skin

UW researchers have developed a flexible, durable electronic prototype that can harvest energy from body heat and turn it into electricity that can be used to power small electronics, such as batteries, sensors or LEDs. One of the drawbacks of fitness trackers and other wearable devices is that their batteries eventually run out of juice, but in the future, wearable technology could use body heat to power itself. This device is also resilient - it still functions even after being pierced several times and then stretched 2,000 times.
Mohammad Malakooti, a University of Washington assistant professor of mechanical engineering, was a senior author of the project.