[Jack]’s design for a 3D-printable foaming nozzle works by mixing air with a fluid like liquid soap or hand sanitizer. This mixture gets forced through what looks like layers of fine-mesh sieve and eventually out the end by squeezing the bottle. The nozzle has no moving parts but does have an interesting structure to make this possible.
Creating a foam with liquid soap requires roughly one part soap to nine parts air. The idea is that the resulting foam makes more efficient use of the liquid soap compared to dispensing an un-lathered goop directly onto one’s hands.
The really neat part is that the fine mesh structure inside the nozzle is created by having the printer stretch multiple layers of filament across the open span on the inside of the model. This is a technique similar to that used for creating bristles on 3D-printed brushes.
While this sort of thing may require a bit of expert tweaking to get the best results, it really showcases the way the fundamentals of how filament printers work. Once one knows the process, it can be exploited to get results that would be impossible elsewhere. Here are a few more examples of that: printing only a wall’s infill to allow airflow, manipulating “vase mode” to create volumes with structural ribs, and embedding a fine fabric mesh (like tulle) as either a fan filter or wearable and flexible armor. Everything’s got edge cases, and clever people can do some pretty neat things with them (when access isn’t restricted, that is.)
Big Clive also has a teardown of such a foaming nozzle soap dispenser thingie.
https://www.youtube.com/watch?v=Y8RCrJ5w5Qk
Interesting!
Thanks for adding it!
Don;t the people who manufacture these things call them aerators?
Thinking about trying this without a 3D printer: https://en.wikipedia.org/wiki/Faucet_aerator
This is an excellent article with great links! Thanks, Donald!
In the article above, you wrote, “Creating a foam with liquid soap requires roughly one part soap to nine parts air.”
However, [Jack] said to mix one part soap with nine parts *water*. Is this some other (unreferenced) fact or have you misread what [Jack] said?
[Jack] was saying that using undiluted soap was too thick to work properly.
He wasn’t talking about the soap/disinfectant to air ratio.
Since I refill my foam soap containers, I find the best mix is about one part liquid soap to three parts water.
Soap manufacturers can sell you mostly water instead of all soap. I think this fact explains why they do it, not that it is necessariy better.