This is a squirt nozzle that mates to most commercial quick-connect adapters for hydration packs or water filters. It is intended to be a small and light alternative to carrying a syringe for performing high pressure wound irrigation in wilderness first aid. It also lets you turn a soft-sided water bottle into a pretty passable super soaker.
(Safety note/disclaimer: aggressive wound cleaning is taught as part of Wilderness First Responder certification and above, and they're only permitted to do it when rapid transport to a hospital is unavailable. This is not intended as medical advice or any kind of substitute for real first aid training!)
The o-rings I used are 8 mm inner diameter, 11 mm outer diameter (1.5 mm thickness) and were found at a local hardware store. When I searched Amazon, a package of 100 was $9, which is more than I'll ever have the patience to print myself.
I typically carry some hose and Platypus soft water bottles so I can use a Sawyer Mini water filter as a gravity filter. Since I am already carrying those, the squirt nozzle is pretty significantly smaller volume than a syringe. The comparison picture is beside the cleaning syringe for the water filter, which is bigger than what you might put in a dedicated first aid kit, but does illustrate the relative size.
It's not uncommon advice to use a hydration bladder as an improvised source of high pressure water, but I think adding a dedicated nozzle makes it a strong competitor to a syringe. The major advantage (if you have plenty of clean water available) is that you can flush a lot of water through the wound quickly, while it takes quite a while to refill and squirt enough water using a small syringe. I think the biggest downside is that it's not as convenient to aim and squirt as a syringe is.
While this was a neat 3d printing object, it's worth noting that you could also easily make a squirt nozzle like this by cutting the tip off a squirt gun and gluing it to a hose barb, or plugging and drilling some hose barb, etc.
Thanks to the Wilderness First Responder students who very nicely played along and agreed to try the 3d printed wound irrigation nozzle hose adapter that their patient just happened to have handy before injuring himself! https://youtu.be/E1Qs5nz8k6M
Print Material, Safety, and Supports
Since I would be using it to spray water on open wounds, these prints were made using an FDA-approved food safe PETG filament. For practical purposes, the plastic is just as safe to contact the water as the water bottles and hose.
I'm pretty sure this wouldn't make them legal to sell with that claim, though. I think the entire printer apparatus would have to be food-contact safe and never used with any non-food-safe filament. I also bet there's additional rules to advertising anything as a medical device, so I wouldn't try to sell these, even though I'd be perfectly happy for it to be used on a wound if I was the patient.
The PETG filament was absolutely terrible for overhangs at any angle. Even a 15-30 degree overhang angle curled severely and created ugly artifacts for the entire print. The filament did well with bridging; that's why you see only right-angled overhangs anywhere on the design. The SCAD file has an option at the top to generate manual supports, and I included the STL both with and without them. The important dimensions are the indentations that allow it to mate with a female quick-connect adapter. Those supports come off easily with an xacto knife. The lower supports are probably beefier than they need to be and took some cutting/sanding to remove nicely.