To print make these:
I used an Ender-3 Printer found here: https://amzn.to/39X2w25
I purchased plastic filament here. Make sure you get right size. Mine takes the 1.75mm https://amzn.to/2Xt2SuT
I used the free program to get ready for printer Cura 4.5 https://ultimaker.com/software/ultimaker-cura
Here are the files sent to me by Shweta Thapa at Maker Depot in New Jersey. The Covid-19 mask is broken down to 3 parts listed here separately. I have also doubled them up to print 2 masks at the same time. That file is called Double. I also shrank them a bit for children size. They are called Kid double. https://www.dropbox.com/sh/0hf8vne2wmn5l94/AAA2R5yY0AMJrhY3erzlEcTEa?dl=0
I bought a HEPA filter that I took apart and cut into squares slightly bigger than the mask square that holds it into place. Here is a link to HEPA filters that are similar to the N95 mask efficiency (block 95% of 3 micron sized particles.)
I bought these elastic braided strands that I tied at the ends. If they are a little thicker, it helps tighten the masks by simply pulling on the ends. https://amzn.to/39SoHqb
Finally, I added a neoprene strip that I reinforced with crazy glue to make a tighter and gentler fit. https://amzn.to/2JP14UF
I am not making any guarantee on these, but I, my family and medical worker friends are using them.
You can reuse, and clean inside and outside with soap water. I am not exactly sure how often you need to replace the filter yet. Some are saying take the filter out and microwave it, for 20 seconds, but I have not tried that yet. Others are saying to spray it with hand sanitizer, but let it completely dry and air out before using it.