A PhD student at Washington University in Seattle, Vamsi Talla, scavenged energy from Wi-Fi signals and used it to power a temperature sensor.
When stored in a capacitor the power was sufficient to allow a surveillance camera to take a picture every 35 minutes.
For the experiment, hot-spots and routers were modified to broadcast noise when not being used for data transmission. This is because Wi-Fi signals are broadcast in bursts across different frequencies which makes the energy too intermittent to be useful.
Powi-fi, as it’s called, is being hailed as an IoT enabler.