Ambient Backscatter
Why Hacker News recommends it
Linked as the original demonstration whenever battery-free or energy-harvesting wireless communication comes up.
What it is
A short University of Washington demo of ambient backscatter, where battery-free devices communicate by reflecting existing wireless signals. It shows devices powered and linked by ambient RF.
Recommended by 0 HN commenters across 0 different months, 2016 to 2023.
What Hacker News said
Cites lucaspiller · 2016-02 · on “Researchers create super-efficient Wi-Fi”
The same researchers released a video demonstrating the basics of this (though not with WiFi) a few years ago: [this video] [LINK]
Cites baldfat · 2017-12 · on “3-D printed plastic objects that can communicate with WiFi devices”
No I quoting a fact not an opinion. Please read my comment and sources before claiming I am factually wrong. "In this backscatter system, an antenna embedded in a 3-D printed object (middle) reflects radio signals emitted by a WiFi router (left) to encode information that is “read” by the WiFi receiver in a phone, computer or other device (right).University of Washington" Screenshot: [LINK] > They're not magically encoding new Wi-Fi packets Yes, these are NEW signals powered by the radio signals that specifically in this article is wifi since it is so widely used. "The chip uses a technique called long-range backscatter to communicate with other devices. Instead of creating signals from scra
Cites tzs · 2021-05 · on “Spin-torque oscillators for WiFi band transmission and energy harvesting”
If you don't need much range (a couple feet, say), you can use ambient backscatter which doesn't need to store up energy for bursts. Here's a video about it from 2013 [1] showing some test devices. Here's an article about it [2]. A bit later they extended this to make it work with off-the-shelf WiFi devices, so you could have a battery-free device that can communicate to ordinary WiFi devices [3]. Still short range, but now you could make it so the reader is a commodity WiFi device like a smartphone, instead of a specialty device. Here are some other researchers who demonstrated a backscatter tag that diddled with Bluetooth Low Energy (BLE) instead of WiFi, and was correctly received by an i
Cites tzs · 2023-09 · on “Sony develops energy harvesting module from electromagnetic wave noise”
It is not just ambient electrical noise that contains usable energy. Others have demonstrated practical sensor energy harvesting from ambient WiFi and ambient broadcast TV signals. I'd expect that the Sony device can probably use those too, so if you've got WiFi in your building you should be fine. If there is ambient radio, you can also use that for extremely low power data transmission from your sensors. The trick there is to not actually transmit any of your own energy. You instead either absorb or reflect the ambient radio. This is called backscatter communications. Here is a video showing a demonstration of both energy harvesting from ambient radio and backscatter data transmission [1].