This tiny Bluetooth chip doesn’t need a battery because it harvests energy from the air
The Internet of Things promises to connect billions of otherwise ordinary devices to the internet, but when each one needs to have its own battery, there’s a limit to how small or cheap they can become.
from https://www.theverge.com/2019/1/15/18183456/wiliot-bluetooth-chip-paper-thin-battery-free-low-cost
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