There is a critical shortage of n95 masks. Not just for ICU staff, but others working in essential services such as emergency healthcare, food production, city transportation, and nursing homes to name but a few. Unlike most cotton masks, these masks are also designed to protect the wearer. I had looked into the possibility of putting my 3d printer to work building protective masks for essential workers.  But the main problem with these types of rigid 3d printed masks is that they do not fit tightly enough to the face.

Normally, a flexible filter material is molded on a special machine and it is this flexibility that allows the mask, when worn tightly, to seal to the face. Regardless of the filter material used a mask is only as good as its seal and the wearer will always be breathing and exhaling through leaks around the edges of the mask and not just the filter. This is a particular problem with generic rigid 3d printed masks.

I came up with one solution to solve this problem using a face scan from a selfie video and began a personal project creating these masks for essential works, friends, and family members. The video above was my first pitch, however, I have since improved the design. I abandoned the box filter in favor of a larger and more reliable pressure fit screw cap. I increased the size by about 50% which was required for more surface area after switching to an improved filter material cut from nanofiber. This new material, branded as Filti, has been lab-tested for use as a facemask material and has a MERV 16 rating, 95% efficiency, and 0.3 microns.

It is really the accuracy of the face scan that allows these masks to fit comfortably and seal so the filter can do its job. Since I was not able to personally visit people to scan their faces, I developed a system where they could capture a quick selfie video of their still face using a penny taped to their forehead. The idea of the penny is to clearly register scale using a common and know reference that everyone has readily available.

From these videos, I could quickly generate a very accurate 3d mesh of a person’s face and use that to model the mask for a perfect fit. I was able to test the effectiveness personally by 3d printing a mask for myself with no filter opening and observing how I was unable to breathe at all when wearing the mask. I experimented with various designs and filter sizes noticing how important surface area became as the micron rating of the filter material decreased. I also found that I could further improve the seal and long term comfort by dipping the hard edges of the mask in Plasti Dip. When wearing the mask I can feel all air inhaled and exhaled moving through the filter. The only time I feel any leaks – usually around the bridge of the nose, is if I distort my face drastically as if yawning or screaming.

I do believe, especially with the new filter material, a custom 3d printed mask could be the next best option for some people when a proper n95 mask is not available. It takes my printer about 12 hours to print each mask so it’s not going to save the world, but It is easily disinfected and is indefinitely reusable so each mask can have an impact. I have been in contact with a few PPE specialists to discuss this design and am willing to produce a mask for anyone who is able to conduct a proper fit test on it.

I originally produced this video to share my idea in hopes that it could be vetted and improved upon and that I might have the opportunity to create one for someone in a position to actually measure and judge it’s effectiveness. I thought it might be most useful for the city bus driver or the person at the meat processing plant, but I was shocked at the number of responses I received right away from front line medical personnel. Many of them were wearing ill-fitting n95 masks or were nervously eyeing their diminishing supply. Some were COVID nurses, ER dentists, and many were family members of people in risky professions. I did make a few of these for people I trusted with a lengthy disclaimer and a plea to make the best decision using the PPE available to them at the time.

I am a software developer, not a PPE specialist and I don’t know for sure how safe this mask is. Because the masks are custom made, it’s likely no single fit test could ever validate this design. Inevitably the effectiveness of such a mask will vary across faces and use cases and it will always be up the wearer to make their own best decision. It has also occurred to me that it could be creating a false sense of security which in itself could make it more dangerous than even a cotton mask. So in the meantime, I have been very selective of who I make these masks for.  I still believe through my own observations that it is effective and I wear one myself occasionally.  But I’m not treating any COVID patients in an enclosed space – I’m just standing in line at the supermarket or sanding the bottom of my boat. But those who are on the frontlines deserve the best equipment available – and hopefully, none of them ever need to rely on prototype 3d printed masks like mine.

exactfitmask@gmail.com