With the supply chains breaking due to the #covid-19 pandemic, some resources are becoming hard to procure. But there are cases when someone’s health or even life, depends on these limited resources. Being a 3D Printer owner, I realise that this is a valuable asset for building things that are otherwise hard to get. Take a face mask for example. With all the 3D printers out there owned by individuals, corporations or makerspaces, we can produce more masks than we could use.
Design a 3D mask that is cheap and only takes a 3D printer and some filament to make
Make it offer the best protection
Make it use air-filters that are 1) easy to procure (even with the curent crises) and 2) are easy to replace
The mask can be disinfected for continuous use
The mask is comfortable to wear
The mask is attached hermitically to the face
This is a call to all owners of #3DPrinters, to use their resources, print these masks and donate them to those in need.
The design started with a pyramid and other primitives that were further processed to match the curvature of an adult male’s face. The filter containers were designed with openings to allow air flow while keeping the filters in place:
As this design proves it is fit , a female version will be made asap. The video already covered all important details, but just to illustrate them again here they are:
- The mask is nicely designed and compact, but the most important thing I contributed with is the sponge adhesive band that seals the mask to the face and also makes it very comfortable. Each masks needs a 35cm band on the perimeter, to make it close hermetically on the face.
- the filter containers can be customised to accommodate a large number of filters, from HME to HEPA. For this demo, my choice was for an easy to procure filter: cosmetic cotton pads.
A military authority in Romania (ACTTM) will be checking the #masca3D for certification soon. Meanwhile more makers are building their own masks. Gabriel did a nice video that shows how the 3d printing process works. This entire print took about 3h30min to complete:
Another idea was to impregnate the cotton pads with anti-microbial chemicals, let them dry, then use them in the mask. When breathing, the the humidity in air would transfer to the chemicals, making them humid and active. I considered the following:
Sadly, all these are slightly toxic when inhaled, so it’s definitely not an option for a face mask filter. But then Ionut sent me this link in Nature.com.
The study shows that a saline solution can act as antimicrobial agent for a similar scenario – single use masks. The filters can be soaked in a saturated saline solution, left to dry, then inserted in the #masca3d filter container. The exhaled air will reactive the hygroscopic salt crystals and enable them to kill viruses. Other salts can be used as well and may have a better yield (Sodium bicarbonate).
There are also wet wipes that some suggested they could be used for filters (packed in several layers). How do all these compare? Here are some microscope pictures, showing the differences. All of them are taken against a powerful light source, so any openings in fabric would show right away.
For all three materials the same settings were used: same background light intensity and distance from source to probe, same microscope magnification.
The Wet Wipes have some big problems, and I don’t think they are suitable for air filtering: the fibres are rare, light protrudes straight through (so will the particles), dragging it even slightly will cause more openings. Also, unless it is washed and dried, there will also be emollients and chemicals clogging the fibres and eventually getting to your lungs. I wouldn’t use this.
The cotton pads have thin and dense fibres. Most important they are long so it is unlikely they will easily detach and fly to your lungs. Light doesn’t get through, meaning the filter has no openings, and the absorbed light going through the opaque disk indicated a good thickness.
The FFP2 Mask comes with long plastic fibres. These will surely work great for trapping incoming particles since an electrostatic effect will easily develop on plastic (also on cotton). They are not so dense as the cotton pads so small particles can find a way easier then through the cotton pads. Also more light propagates through the opaque material as in the case of the cotton disk.
How’s the winner here? Check the photos and decide for yourself. It is obvious the cotton disks are a nice alternative, easy to procure and easy to replace. The mask’s containers allow for two stacked disks, doubling all this and exceeding the FFP2 by far.
But there are many other options here. The containers can be customised for any filter combination, depending only on what it can be sourced on the local market and stock availability. For sensitive applications, instead of the existing containers, you can use HME filters , here’s an example made by Teo, who used two Draeger HME filters. Their datasheet indicates stopping 99.99% of viruses and bacteria. And they fit right away, with no other modifications:
I did a few tests to determine how comfortable the mask is when wearing it for a longer time. After 2hours there were no marks on my face, breathing was ok (yet, I could feel the air being limited due to filtration), there was a little condensation inside but the filters were still usable (not even a little moist). The rubber is important for comfort and so is the sponge band used to seal the mask to the face. Video in Romanian:
Lots of makers started building their own. You can go for plain white or add some colour, here are some ideas:
Here’s a video (in Romanian) about how 3D printing is done, how well are welded together the layers that make up the mask, a water test, images under the microscope and finally, a test with a thermal imaging camera that shows where the air comes in and where the air goes out to illustrate the face sealing performance.