That’s what being a parent does to your sleep schedule…
Hence why I never got married or had kids… I’m a bit of an insomniac already…
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You need to consider that the scalpel is harder than the titanium and will scratch it easily.
As I sent you in the DMs, it is just aluminum oxide sandblasted. You see me in the video scratching the blank, polished titanium, and I’m also getting flakes of it on the scalpel.
We got data from the manufacturer, which says it is only aluminum oxide sandblasted.
I think what we are seeing is just sandblasted titanium, and you are scratching it with the scalpel, which is harder. That surely makes material come off, and since the surface is so coarse from the sandblasting, more material comes off than on the polished side.
In my video, you see me scratching just the shiny side, and the scratched off stuff looks similar.
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What about one of those laser rust remover gun things? Looks like they would be pretty simple to setup and get repeatable results
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If I remember correctly aluminum oxide dissolves in (low concentration) sulfuric acid much more readily than titanium, though I believe titanium will form an oxide layer from it. Not sure how that will react with flesh but I think its out of the question.
Anything else we could use to chemically make sure no aluminum oxide remains while leaving the titanium intact?
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Is loose aluminum oxide toxic or hazardous?
What would happen if you just left it on there anyways?
Definitely seems like it’d be nice to have it gone, just curious worst case scenario
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From my understanding, depends on the person. This is not one-to-one applicable, but you get the idea. Allergic reactions, along with some risk of short term itchiness etc (assuming a low amount of elemental aluminum, which I think is safe to assume).
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Maybe let’s all take a step back and consider that removing it might not be useful in the first place?
What is the exact reason we don’t want the rough side?
Toxicity? No, the materials involved are not an issue. If they were we wouldn’t be trying to “scrub off the loose bits”.
Roughness? No, most of the solutions proposed will leave behind a rough surface and that doesn’t seem to bother anyone. In fact it might be interesting for sensing as mentioned above.
The fact that it flakes with a scalpel? I’m not convinced this is relevant at all. Scrape any coating with a scalpel and it will take bits off 
@mrln demonstrated this happens no matter if shiny or textured.
Just just to contextualize, scraping with a harder, sharper blade is nowhere comparable to the behavior in vivo.
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I would be more concerned with the loose bits coming off. Scraping aside.
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That is simply not a thing on any relevant scale when in contact with flesh.
It’s a result of scraping a softer, rougher metal with a harder, sharp scalper blade.
That’s exactly my point.
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I think it’s pretty clear that we’re all operating in the realm of opinion at the moment, not scientifically rigorously tested fact… and I state as much here;
We can look at papers and point to snippets, but this is not scientific rigor. In lieu of the necessary rigor to definitively answer questions like “will particles of ALO3 or TiO2 come loose from the treated surface while in the body” or “are loose particles of ALO3 or TiO2 safe to float around in soft tissue”, I am simply going to focus on deriving a process that makes me feel better about putting one in my body and in turn, selling these to people… that’s all. It’s a personal preference thing for me and for DT.
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That’s fair. Have you found other manufacturers? Sounds like the most cost efficient thing would be to find a source that doesn’t have the extra processing. There are definitely a couple around
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Finally had the time to look at the videos properly, and I don’t like that small balls of material are left behind. However, I suspect that most of what the blade is scraping is the small bumps of titanium that the sandblasting process creates.
I wonder if the corrugated surface could encourage biofouling even if all of the aluminum oxide is removed?
I’m making a lot of assumptions here as I don’t have one of those magnets to mess with so take this with a pound of salt.
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This is not strictly a proposed solution, more of a loose idea here. I wonder how well an ultrasonic cleaner would remove any loose titanium and (possibly) aluminum oxide remnants.
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I was thinking about another solution; back in the day when I etched my own PCBs, I used to clean the raw boards with steel wool. While etching the boards, the ferric chloride quickly removed all the scratches and turned the surface into a matt and smooth finish.
I was doing this until all of the unwanted copper was gone so things were a bit different from what’s needed here.
What about lightly etching the titanium until the sandblasted surface is eliminated? Are the magnets accurate enough out of the factory to allow measuring them after etching to make sure that there’s enough titanium left?
This process will probably take a few jigs to get right. But most importantly, a separator so that the magnets don’t stick to each other during the etching bath. Hopefully these can be 3D printed.
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well, maybe i’ve watched too much youtube but I think there’s an easy way to check if it’s titanium or aluminum oxide. find something with a hardness that’s higher than titanium but lower than aluminum oxide, and try to scratch it with whatever is coming off the scalpel.
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The reason they use this material is because it is harder than Titanium. Otherwise it wouldn’t be a good abrasive for sandblasting : )
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Sorry, might have written that in a slightly unclear way, but that’s exactly what I meant we could use to determine if what’s being scraped off is just the titanium or the aluminum oxide. Remove the scraped off material from the scalpel, place it on a piece of some other material with known hardness that’s between the other two, slide it across and see if it leaves a groove.
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With fines? I think the margin for error on something softer than Titanium is high–brass, btw. We already ran through this : )
Regardless, as @amal pointed out we are steaming along with what is felt is the safest course of action rather than dumping more resources into finding out that we’ll probably have to do it anyway : )
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