This tiny Bluetooth chip doesn’t need a battery because it harvests energy from the air
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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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