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N95


Masks.. an essential tool in the 2020s

One has seen the importance of masks to fight against diseases and the spread of viruses. Have you ever wondered how masks work, specifically the N95 masks? You might be thinking, all masks are like a mesh of fibers with gaps too small for dusts and other airborne particles to get through. But what’s so special about the N95 masks?

Now a regular masks do filter out large particles, but a small enough particles are allowed to sneak through. N95 is much clever than that, it filters out tiny particles even though the particles are much smaller than the gaps between the fibers in the mask. First of all, the fibers in the N95 masks trap the airborne particles once the particles touch the fibers, so think of the fibers in N95 masks as a sticky spider web.

To make sure that the fibers catch as much particles as possible, many layers of sticky fibers means more chances for particles to get stuck. How likely is the particles to get stuck depends on their size: large particles (often travel in straight line) will get trapped easily in their straight line path; tiny particles (travel in random zig-zag pattern known as Brownian Motion) also very likely can bump into a fiber. What’s difficult are the medium-size particles (carried by the air and flow around fibers), which can bypass and sneak through many fibers.

N95 masks have another trick: the fibers are charged with static electricity, like a magnet (but for electricity). In the presence of electric field, even neutral particle can develop electrical imbalance which attracts them to the source of the field (attracts 10 times more particles than regular fibers). N95 does a really good job at capturing large and tiny particles (100%), as for medium-sized particles (95%), hence the name N95!


Keywords

  • Brownian Motion: A random motion of a particle as a result of collisions with surrounding gaseous molecules. Diffusiophoresis is the movement of a group of particles induced by a concentration gradient. This movement always flows from areas of high concentration to areas of low concentration.

  • Electric Field: An electric field is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them.


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References

https://www.youtube.com/watch?v=eAdanPfQdCA
https://www.sciencedirect.com/topics/chemistry/brownian-motion
https://en.wikipedia.org/wiki/Electric_field