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ek slash special offer. This is Scientific American 60 second science I'm

Christopher Intagiata One of the biggest drawbacks to wearing a smart

watch is how often you have to take it off to charge it. But here's an idea. How about charging it

with a power source that's pretty ubiquitous nowadays.

Wi-Fi signals are all around us and most of them are just wasted.

Shujong, an electrical engineer at MIT.

Writing in the journal Nature, he and his colleagues

describe a device called a rectenna,

designed to capture energy from Wi-Fi signals

and turn them into direct current electricity.

The rectenna consists of a small gold antenna, about the size of an

SD card, which converts a variety of wireless signals like Wi-Fi,

Bluetooth, and cellular LTE into an AC signal.

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