So it sounds like a single-component process, no powder bed or vat of hardener liquid. "Silicate solution" presumably means waterglass rather than something like tetraethyl orthosilicate, and if it hardens rather than foaming up at 250°, it's either because they're doing the process under pressure or, more likely, the other inorganics they mention are donating polyvalent cations such as Ca⁺⁺, Mg⁺⁺, Al³⁺, or Fe³⁺ to crosslink the silicate residues.
Probably the polyvalent cations are bound up in a salt that has negligible solubility at room temperature, so the ink doesn't harden in the reservoir, but which can react with the silicate at 250°, maybe a hydroxide or carbonate. Calcium sulfate is probably too soluble.
Presumably the silica filler is amorphous and serves to strengthen the glass and reduce the TCE, though it probably raises the cost. Maybe it also makes the paste thixotropic without needing to include organics like carboxymethylcellulose which would be hard to remove later. And I guess maybe it could react directly with the waterglass to solidify it, in effect raising the waterglass's modulus out of the water-soluble region, without requiring any polyvalent cations. Silica fume is the most likely form of silica here.
If anyone digs up more details, I'd love to see them.
The patent says, "curing the material to evolve gaseous water," which makes it sound like thick sections would foam up. (You have to heat it over a length of time quadratic in section thickness to permit water to diffuse through the nascent solid.) And supposedly that is the purpose of the heating, rather than provoking the other reactions I speculated about above.
There are some interesting notes in the patent about promising functional fillers, such as carbon fiber for strength or silver flakes or conductivity. It suggests using these inert fillers at loadings of 45% to 90%.
It confirms that the silica is fumed silica, and suggests as alternatives fumed alumina (sapphire) or fumed titania (rutile or anatase), which are not products I had heard of, though titania nanoparticles are common as a white pigment in paint and in food. Waterglass can definitely crosslink with aluminate sources such as metakaolin, as used in "geopolymer cement". Titanate is news to me, if true.
It also confirms my inference that the fumed silica makes the ink thixotropic, at 15 wt%, though it uses the phrasing, "introduces a yield stress into the material" and "shear-thinning behavior".
I'm definitely going to use that phrase the next time I'm making mayonnaise.
"Why are you stirring that bowl of egg yolks and oil with a fork?"
"I'm introducing a yield stress into the material!"
The patent also confirms my inference that the silicate solution is waterglass; it specifically says sodium silicate (or ammonium silicate, which is probably not a practical possibility: http://www.sciencemadness.org/talk/viewthread.php?tid=10297)
The patent doesn't suggest using ionotropic gelation in the way I suggested at all. It doesn't mention the mineral oil either.
Interesting. I wonder if this could be used to print telescope mirrors if you could get an "ink" that has high thermal stability, or if that would be in conflict with the low temperature printing.
That seems like it would be very difficult. For a telescope mirror you want a very good surface finish, and that's one thing that 3D printing does very poorly.
The polishing process could be done differently. If you could print the specific parabolic shape, that could save a lot of time hogging out. Although slumping might work better if surface ends up smoother. Im not sure of the annealing process might go.
The parabola of a telescope mirror generally deviates from a sphere by tens of micrometers at best. Figuring happens after grinding and after polishing. Slumping is neat, but I've heard from the grognards that they can shatter if the temperature changes too quickly.
There's a few combined-process setups coming out these days that use 3D printing as a first pass and then machine the print in-place before sintering etc. which saves a ton of setup and fixturing time.
Yes! This is exactly what I had in mind. Sintering (thanks for the term) combined with this 3D printing technique could still make the process faster and lead to more consistent results.
Now that’s I think about it, one could in theory use the exact same process for plastic-polymer lenses too, albeit at lower temperatures (better).
Maybe with further augmentation to the process. The 3D printing seems to leave pretty big grooves on the glass - which can distort the passage of light. For any real optical application, that will have to be removed somehow. Such as baking the glass structure in a high heat oven with a centrifuge/fast spinning base and some kind of mould to put the initial piece on.
The high heat and spin action could, in theory, fuse the individual grooves for a more uniform dispersion of light, and the mould shape would further press on the glass to maintain or alter its shape to be closer to a lens.
Finish that off with fine “sanding” and/or polish, and that might do the trick?
Honestly, experimentation might be the only way to find out.
but if you want to plqy with some, it is readily avail8ble as a "cement" used for attaching seals to wood stove doors, and countless other low teck applications
the comon name of "water glass" refers to it's solubility, so.....
That's not what this is. Sodium silicate is part of the process but so are lots of other things. The patent is posted here in the comments that would be a good place to start if one wanted to experiment with it.
Probably the polyvalent cations are bound up in a salt that has negligible solubility at room temperature, so the ink doesn't harden in the reservoir, but which can react with the silicate at 250°, maybe a hydroxide or carbonate. Calcium sulfate is probably too soluble.
Presumably the silica filler is amorphous and serves to strengthen the glass and reduce the TCE, though it probably raises the cost. Maybe it also makes the paste thixotropic without needing to include organics like carboxymethylcellulose which would be hard to remove later. And I guess maybe it could react directly with the waterglass to solidify it, in effect raising the waterglass's modulus out of the water-soluble region, without requiring any polyvalent cations. Silica fume is the most likely form of silica here.
If anyone digs up more details, I'd love to see them.
Hmm, I see gsf_emergency_2 found this patent from 02020: https://patents.google.com/patent/US11499234B2/en which is later than Dercuano but earlier than Derctuo and Dernocua. But its priority date is from a provisional patent application from 02019, so even Dercuano doesn't count as prior art, even if it anticipates some of the claims. Also, though, I don't see anything that anticipates this process in notes like https://dercuano.github.io/notes/flux-deposition.html and https://dercuano.github.io/notes/powder-bed-3d-printing.html, which suggests that it wasn't as obvious as it sounds.
The patent says, "curing the material to evolve gaseous water," which makes it sound like thick sections would foam up. (You have to heat it over a length of time quadratic in section thickness to permit water to diffuse through the nascent solid.) And supposedly that is the purpose of the heating, rather than provoking the other reactions I speculated about above.
There are some interesting notes in the patent about promising functional fillers, such as carbon fiber for strength or silver flakes or conductivity. It suggests using these inert fillers at loadings of 45% to 90%.
It confirms that the silica is fumed silica, and suggests as alternatives fumed alumina (sapphire) or fumed titania (rutile or anatase), which are not products I had heard of, though titania nanoparticles are common as a white pigment in paint and in food. Waterglass can definitely crosslink with aluminate sources such as metakaolin, as used in "geopolymer cement". Titanate is news to me, if true.
It also confirms my inference that the fumed silica makes the ink thixotropic, at 15 wt%, though it uses the phrasing, "introduces a yield stress into the material" and "shear-thinning behavior".
I'm definitely going to use that phrase the next time I'm making mayonnaise.
"Why are you stirring that bowl of egg yolks and oil with a fork?"
"I'm introducing a yield stress into the material!"
The patent also confirms my inference that the silicate solution is waterglass; it specifically says sodium silicate (or ammonium silicate, which is probably not a practical possibility: http://www.sciencemadness.org/talk/viewthread.php?tid=10297)
The patent doesn't suggest using ionotropic gelation in the way I suggested at all. It doesn't mention the mineral oil either.
Is the year in octal (/s), or do you truly believe we're due to survive eight more millennia with the same year numbering system?
It seems very optimistic and 90s to me now
I wonder what the other inorganics ("functional additive, embodied in some cases by Silver flakes") are, exactly. In their flagship product.
And the size of the nozzle, why not the easier to remember 400 micrometers?
> The ink can be extruded through a nozzle 604 (e.g., a 200 μm, luer-lock tapered nozzle)
Now that’s I think about it, one could in theory use the exact same process for plastic-polymer lenses too, albeit at lower temperatures (better).
The high heat and spin action could, in theory, fuse the individual grooves for a more uniform dispersion of light, and the mould shape would further press on the glass to maintain or alter its shape to be closer to a lens.
Finish that off with fine “sanding” and/or polish, and that might do the trick?
Honestly, experimentation might be the only way to find out.
https://en.wikipedia.org/wiki/Water_glass
but if you want to plqy with some, it is readily avail8ble as a "cement" used for attaching seals to wood stove doors, and countless other low teck applications the comon name of "water glass" refers to it's solubility, so.....