I built a mmWave material classification radar (2025) | Hacker News Reader

I built a mmWave material classification radar (2025)

gauthier-lechevalier.com

203 pointsGL2660 comments

> I live in Europe, where asbestos is a huge and common pain across every country here. That stuff fills walls, and requires people to come at your place to tell you if you have asbestos contaminated materials in your building. If so, you might have been breathing poison since you were a kid.

Asbestos doesn't work like that. If you don't touch it, you're fine. You can live your whole life in asbestos building and be safe. You may even be worse off if you decide to get rid of it and start tearing down walls.

So it's good that it's banned, but if there's no reason to touch it, you're just making a tinfoil hat. There's more harm from the fear of it.

It’s not that straightforward. Asbestos comes in many forms with varying friability. Mixed into linoleum floor tiles? Probably not a big deal. Mixed into wall plaster in a poorly maintained rental unit? A hell of a lot riskier. And a lot of the buildings that have asbestos-wrapped pipes, for example, have cramped utility crawl spaces and basements that can make it difficult to avoid. If you’ve got asbestos hidden behind a stable and well-maintained wall, or on utility lines that are easily avoided, then whatever. That’s frequently not the case, however.

The single largest use of asbestos here was in fibre cement cladding, which is fine if you don't decide to cut or drill into it. In fact given that it's nearly indestructible and will wear most saw blades and drills down to a stump in about 5cm of cutting, you couldn't cut/drill it even if you wanted to. Neighbour of ours wanted to put in a serving hatch outside his kitchen and after about 20 minutes of attacking it with all sorts of devices gave up and decided they'd just pass stuff out through the window instead.

Yeah that’s not friable asbestos. People only care about friable asbestos, which is a huge problem in many places.

Very cool! Six years ago I worked on a mmWave (76-81GHz) imaging radar with a Rotman lens Tx and Rx. Designed as a LiDAR replacement, but we could see pipes in walls, or detect concealed weapons at ~1km.

Do you have a writeup about the project? I'd love to read more about it.

Super cool. Didn't even know mmWave was used for radar and imaging techniques!

Isnt mmWave pretty similar (in theory) to short-ish range wireless directional antennas? What people used to call point to point "microwave" transmission?

Crazy idea but could your mmWave radar hardware also be (not simultanouslyl) used to transmit data? No idea what a Rotman Lens is but I would imagine that maybe it could be useful for transmission as well.

isn't mmWave the thing they use at the airports?

Yes it is!

I've been down the mmWave rabbit hole for the last 6 months, making sensors to put around the house to control automations for lights and so forth. They're pretty great.

For my use case the advantage over PIR is they do presence detection, so no more lights shutting off when you're sitting on the toilet.

Pretty amazing you can pick up basic mmWave sensors for a few bucks on amazon, and mate them to an esp32 board which is another couple bucks. It's so much fun as a hobby!

Believe they do use a good amount more power though (mainly only an issue for battery based devices)

Mate this is genius! How have I not thought of mmWave detection. Rabbit hole activate!

Waiting for an M413 motion detector to be commercially available.

How many tx and rx antennas did you have ? (I don’t know if it was clear, my stack was 57-64 GHz, 2TX , 3RX)

32 port Tx (vertical pancake beams) x 16 port Rx (horizontal pancake), something like 60 by 30 degrees. the entire thing used FPGA transceivers as one-bit DAC/ADC, Complementary Golay Code waveforms with one-bit correlation in the FPGAs (two VCU128s) -- digital logic was essentially the same as a binarized neural network, I squeezed a ton of popcnt performance out of those chips using both DSPs and LUTs

Err holy shit that’s quite the array and FPGA processing backend. I assume the purpose of the system is secret?

(VCU128s are relatively large, HBM equipped FPGAs for people not aware)

It was designed for automotive as a replacement for LiDAR, also useful for finding metal FOD on runways, or concealed weapons and I suppose also liquids on travelers walking in an airport...

(Linked VCU128 digital radar was cool but even cooler is using them as digital array beamformers and sending RDMA over fiber into a quad A100s nvlinked to do the whole radar DSP pipeline)

What project was that for ?! Sounds super cool

Get this guy into YC. He knows how to do it, but not how to sell it.

This needs to join the families of devices that find wooden studs, electrical wiring, and plumbing. This is a general purpose technology. It can be reprogrammed to find other things. It should be in a blister-pack at Home Depot if it can be made cheaply, and in a hard case at Tool Town if it can't.

Is there anything that reliably finds wooden studs in walls? I've tried a whole range of different stud finders and all of them are at a level of reliability roughly on par with the Psychic Friends Network: "I think there may be something there... or is it over there? No, perhaps there".

In the end the most reliable way of locating studs I found was going outside, measuring the distance between the nails in the exterior cladding, and then using those measurements on the corresponding inside wall.

Cheap thermal camera lets you literally see the studs. Does not work when ambient temperature inside is the same as outside though

Good point, I've used that to find all sorts of things inside the walls. As you say, it works best when there's serious thermal bridging going on.

Receptacle boxes are nailed to studs, once you locate one you can find the others along that wall if you know the stud spacing.

Magnets find studs pretty well in my experience

Experience and tapping with your knuckles :-)

Hi, thank you so much for your comment, the research was cool to do, but the market isn't there, and this is not something people really want (to retake YC's wording). You can have all the tech you want, but at the end of the day, the important thing is to have something that really brings value to your customer

Property managers handling municipal property in mid+ cities will want one.

Any company dealing with construction waste disposal will want one.

Both will have no problem shelling out 1000 euro per unit.

I interpreted the comment as “give this guy some money and he will figure it out”. You have some serious skill, this just wasn’t the right idea.

Needs a team with someone who works on product fit and market evaluation. A handheld device that analyzes hidden materials cheaply has a market. Microwave beam-forming and neural nets in a handheld device at a low cost is new technology. And get a patent, or there will be cheap ones from Shenzhen.

Don't listen to YC. Reach out to Bosch.

there is a dutch DIY reddit group and the most common daily post is: Is this asbestos? if there would be a 20-50 euro device to confirm this im sure plenty would buy it

So thankful the author posted this. We often learn more from failure than success. Learning from the failures of others is how we can move forward. The lessons learned at the bottom of the article are gold.

thank you so much for your feedback, it was hard to admit defeat, but at the end looking back at what I built, the parts where I learnt about RF, and just struggled, refactoring the code for the sim (thank god cc is not good enough to understand real world physics functionning for now) were the most satisfying moments

Was this AI comment necessary?

If you'd like to learn more about the module:

https://www.ti.com/tool/IWRL6432BOOST

Edit: maybe I am seeing AI everywhere! False positive. :-)

Your comment still has a lot of value, I didn't detail it in the article but this radar is usually used for autonomous vehicles, or person tracking.

> however the big question to answer was : is the radar sensitive enough to tell the difference consistently between a material, and it's same counterpart with asbestos shards and at what concentration ?

Unless I missed something, it seems the "POC" device still made no effort to address this, which is the core feature — it just demonstrated classifying some other common materials. If that's true then the conclusions make no sense to me - why would customers be lining up if you still haven't proven the actual concept?

At least in the US (and this probably is different from Europe) it matters a huge amount how the asbestos is exposed to the environment. Asbestos that's sealed up generally gets (a) labelled so noone cuts into it (b) sealed up even further - but if it's exposed, the evaluation is more about "can it get into the air" (sealing is again the preferred step, epoxy over tile, that sort of thing) - actually removing it is a last resort. So "mere detection" is a really small part of the problem.

(Of course, the place I've dealt with this the most was a former post office building from the late 1930s - we didn't really need tests, a historian would probably have just said "of course you have asbestos" :-) It does expose an interesting problem with the labeling part, though: USPS as an ancient federal agency has its own rules for things and had a distinct asbestos markers - an A in a point-down triangle - which we fortunately found documentation for, it isn't public record.)

The POC was made to classify materials, we couldn't get our hands on scientific grade materials that would allow to test our hypothesis, so we falled back to just identifying materials. We even went to identifying multilayer materials. You are totally right, this is not a true total POC, it's like the "level 1" of the POC needed to prove this was possible.

Very cool idea.

I'm sure this can be annoying when people do this, but I can't help myself lol. I wonder if you could operate in a different modality and find discontinuities in material properties rather than use it as a classifier. For some reason skin cancer detection popped into my head, but general purpose inspection/detection cases for any discontinuities might be pretty helpful. Depending on the resolution/size of the field it's inspecting a realtime camera overlay might be interesting for correlation sake.

the FMCW tech makes it impossible to have a resolution inferior to 2.5 cm, (so if two layers are appart, you can't physically tell them appart using physical classical modeling techniques with DSP). However, you can use AI to enhance the performance of the system, and make what you are saying possible. The downside of AI is that you need tons of data, which is expensive to get.

imaging spectroscopy is a potential solution--it's been studied for over 30 years.

Hugged to death but I'd love to see this!

Kinda crazy that it worked but got no commercial interest. Hopefully someone suitable here sees it and can intervene

Does it also work through other materials. i.e. through a drywall etc.

I can't say that I believe that it works.

Like if you trained a machine learning algorithm to differentiate 10 samples of asbestos containing material from 10 non-asbestos containing materials I wouldn't believe it would work with all the many kinds of materials you would find out in the field in all the configurations that are out there.

All that talk of how the electromagnetic properties of asbestos-containing materials are different are pretty handwavy and lack a theoretical explanation of where the dividing line between different materials ought to be. Overall it strikes me as the kind of half-baked idea that people suddenly feel empowered to do thanks to AI.

Yes, it is half baked, we stopped because the quantity of data needed to continue was too expensive. Concerning the materials that were in the confusion matrix that you saw, it was only non asbestos materials (plexiglas doesn't ever contain asbestos for instance). The confusion matrix that you saw was made to prove you could identify different materials from one another, we never went as far as getting two same materials and one with asbestos minerals inside it.

About AI. Two things you learn in school : for centuries, we measured the world and modelled it using differential equations, and other mathematical concepts. Humans just have a certain limit to finding patterns, and this limit is covered by AI, which when you come to think of it is just a series of calculations to model statistical phenomenons.

Physics is a statistical phenomenon, therefore AI is now being used everywhere in physics to model the world.

It's a cool technology, but for it to gain commercial interest it needs to solve a problem better than the status quo. What problem is it solving and for who? If I was to buy that mmwave radar device it would probably cost more than the $60 test, and I would want assurances that it is as accurate as existing tests.

exact, if I was carrying a PhD (which I am not). I think I would have wanted to go out further and get more data to make this device pass regulatory tests. What was the status quo we were solving for ? An asbestos analysis costs around 60€ per sample in Europe when you ask it to a professional asbestos diagnoser. One use of our radar cost litterally the cost of an API call, so we were definetly beating the status quo. The big challenge around this was actually who is the customer ? We initially wanted to sell it to the pro diagnoser, but in France there is some sort of tacit agreement between diagnosers and asbestos labs to keep prices high on purpose (because it advantages both of them), they protect their business well and put high regulatory gates around this. Building a tech startup isn't just about overcoming the tech barriers, but also regulatory barriers which are often really underestimated.

Looks like he succesfully pivoted: https://waves.black/ and he is building an OTA update framework apparently now : https://www.nanoforgeflow.com/

The guy is scrappy.

overtech for a problem that had a solution (asbestos sensing is pretty painful in Europe), but anyways the market was shrinking, and the TAM was totally not VC backable. Tested it out with : wood, copper, alumnium, paper (the book you saw), stone, PVC, plexiglas and air

My dream (actually one of them) is to one day build a wall-e that can collect trash from the environment. This is exactly what I would need for it!

you could definetly equip you wall-e with this sensor, but honestly a camera with yoloV26 + fine tuning for trash recognition would be enough

That's awesome. I built one for a capstone back in the day and know how tough it is to get onboarded. Kudos.

love the background music in combination with the flying fishes wallpaper in the first video haha

very cool project

hahaha ! oops didn't mute the video, would blast trap music when I was alone in the lab x)

Terrific project!

thanks :) !!

My netlify crashed fixing the website rn

just fixed it, hope it works

small note : the website wasn't coded to handle such a trafic, I had to inject a few netlify credits to keep the website alive. The videos are now linked on youtube (they are initially unlisted). Got actually ddosed by HN (good problem to have haha)

Not a hotdog.

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