“The smart lock on a front door may not draw much power, but the Internet of Things (IoT) is expected to grow to 50 billion devices by 2020. Such devices include activity trackers, smart bulbs, every Alexa-compatible device, etc. Taken all together, that network of connected devices will pull a significant amount of electricity. Currently, they all have to be charged or left tethered to a power source. But new research out of King Abdullah University of Science and Technology (KAUST) may enable IoT devices to power themselves from energy captured from other wireless communication signals…”

Source: https://www.3ders.org/articles/20190201-harvesting-energy-from-wireless-signals-to-power-3d-printed-iot-device.html