They engineered a nanoparticle that was the same size and character as COVID-19, but fluorescent, so you can see it with a special microscope. They then took two milliliters of the nanoparticle solution — the equivalent of about two dozen sneezes in water droplets — and put it into an artist’s airbrush. The air leaving the airbrush creates an aerosol that’s passed through the test material. On the other side of that is a glass slide to pick up any particles that made it through. Using a fluorescent microscope and an algorithm, you can count the nanoparticles on the glass and then compare that to the number of particles that would have gone through without any material or with N95 or other medical masks that have already met rigorous standards set by the American Society of Testing and Materials.
“We really calibrated our technique based on masks that had already been certified,” said Lustig. So far, he reports that they’ve found nine designs that are statistically equivalent to N95 masks — and two that are better.
The ideal made-at-home masks need an absorbent layer composed of something like quilted cotton, terrycloth, dense flannel, a heavy T-shirt, etc. You also need at least one layer that’s hydrophobic, meaning that it repels water, such as a polyester fabric like OLY-Fun, preferably treated with Scotchgard. The more layers you add, alternating back and forth, the better you are protected.