If I understand this correctly, this is a paper about 3D printing physical objects, with no electronics, that send information over wifi.

ie, magic.

This is magic.

@ajroach42 also, I’m not sure why most of the comments on this have been pedantic hairsplitting over what qualifies as WiFi or what qualifies as electronics.

They use WiFi signals and the resulting modulated data can be read with a WiFi radio. That means they use WiFi, even though they aren’t sending packets.

The devices are unpowered, and basically just mechanical devices attached to cleverly built antenna. If you want to call an unpowered antenna electronics that’s fine. I don’t.

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Either way this has the potential to dramatically change the way low/no powered sensors are built and deployed, which has the potential to be revolutionary.

Save your pedantry and your hottakes for someone else.

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@ajroach42 from the extended video it looks like they're using ambient backscatter

So for my level of understanding, JFM, but it seems to be workable

@ajroach42 Something to do with copper impregnated filament disrupting wifi RF waves in very specific ways?

Pure magic. And I look forward to eventually printing this stuff.

@ajroach42 not really sending information over wifi (backscattering, producing radio signal that doesn't really have anything to do with wifi), but yeah, magic.
I'm curious how well it works, and what is involved on the receiver end (haven't read the paper yet)


According to the video, the goal is for the backscattered signal to interact with wifi receivers, unless I'm misunderstanding something.

@ajroach42 @Thib In the first few pages, I see no reference to "wifi receivers". They very carefully always say "RF receivers including WiFi".

@kurtm @Thib

At some point, the difference between a "wifi receiver" and "RF receivers, including wifi" is splitting hairs, yeah?

Like, I understand that wifi is a specific protocol that uses a spectrum shared by lots of other devices, and that without the ability to generate more complex signals it won't actually be "wifi" but if a standard wifi radio can receive these signals and be made to understand them, wants the point of the pedantry?

@ajroach42 @kurtm the thing is, it will only fall in the same range of frequencies as WiFi, but the modulation has nothing in common and it will completely ignore the protocol. So it's far from obvious how WiFi receivers could handle it.

@ajroach42 @Thib There is no comma. It looks like they are talking about boxes that collect signals from these things and pass that on to Wifi. Like a bridge.

If I get a box talking RS232 to a host with wifi, I can claim it talks to "signal receivers including wifi". It's not speaking wifi. The host is speaking wifi. Using that specific awkward wording was a big tell to me.

I mean, it's very cool stuff, but it's not things without electronics speaking wifi.

@kurtm @Thib

I haven't read the paper yet, so I can't speak to the specifics beyond what they included in the web page and their powerpoint.

The website says "Our goal is to 3D print wireless sensors, input widgets and objects that can communicate with smartphones and other Wi-Fi devices, without the need for batteries or electronics."

@Thib @kurtm

Now, based on my understanding of how wifi works, they would need direct control of the radio, and to write a custom driver in order for the data their devices produce to be readable by a smartphone.

It wouldn't technically happen over wifi, but to an end user the difference wouldn't matter.

@kurtm @Thib In the situation you're describing, there is a receiver other than the smartphone sitting between the device producing the signal and the wifi receiver that would receive and interpret the signal, and send the results out over wifi.

At some point, I'll actually read the paper and verify.

The neat thing here is that they are generating the signal without electronic components or electricity.

3D printing a sensor that can passively communicate is a big deal.

@Thib @kurtm
I skimmed the paper for the section that deals with the wifi receiver, and it looks like basically we were both wrong.

There's a wifi transmitter, and wifi receiver, and between them, the sensor.

The sensor modulates the wifi signal passing between the wifi devices.

The differences between the unmodulated signal and the modulated signal are decoded by a device at the receiving end.

They go in to the details in section 3.2 of the paper.

@ajroach42 @kurtm quickly went through that section of the paper, pretty much what I expected. They do use existing WiFi hardware for decoding signals, though. That's pretty impressive.

@ajroach42 The same technique can be used (probably is being used) to turn your wifi into passive radar, revealing location & activity information about everyone in the house to a snooper outside. yep. I read about that a few years back.

Also magic, but pretty scary magic.

@ajroach42 Wow !!! it looks like magic but i'm not sure I've understood how it is received on wifi side ? I think it requires a specific module on receiver side to decode the information?


@valvin @Lapineige

The details are covered in section 3.2 of the paper, which is linked from the page.

Basically, it uses a wifi transmitter and a wifi receiver. The transmitter is unmodified. The receiver is connected to a computer that is analyzing the data from the wifi receiver to look for the modulated signal from the 3d printed sensor.

Basically, they are using standard wifi hardware, with custom software on the receiving end.

@ajroach42 *squints suspiciously* OH interesting. Using: which uh... *is* electronics tyvm. Someone needs to pop them on the nose with a newspaper. All they're doing is non-commercially printed circuitry.

@bastlynn the neat parts here are 1) this was done with readily available 3D printable material. 2) the circuits they print don’t require a power source beyond ambient WiFi signals, because they’re basically antenna. 3) the receiver doesn’t require any special hardware. Just WiFi and some custom software.

These things are neat! With some refinement they could be practically revolutionary.

@ajroach42 I didn't even know these filaments were available. It really does lead to some interesting things re embedded circuits.

@bastlynn for sure, although the resolution of current 3D printers limits the practicality in a lot of situations.

I’m still waiting on 3D printers profcessors.

@ajroach42 Basically looks like they're printing RFID antennas and maybe using the internal resistance of the positions of the objects they print to convey data measurements?

@bastlynn the linked paper goes in to all the details, but it’s a little more complex than that, unless I really misunderstood how rfid works.

@ajroach42 the main issue I could see with this is longevity due to wear on the coil spring

@theoutrider yep! But the spring is made out of abs, and abs is super cheap.

When the spring wears out, you grind it up, extrude it in to new filament and print another, right?

@ajroach42 I'm all over that.

Thinking about this for my next project!

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