The Astounding Physics of N95 Masks

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This video was written in collaboration with Aatish Bhatia – https://aatishb.com
To learn more about using & decontaminating N95 masks: https://www.n95decon.org

Thanks to Manu Prakash for useful discussion and feedback (Manu is involved with the N95 decontamination project)

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The physics & engineering of N95 mask design is pretty incredible.


10X efficiency of electrically charged fibers

“The electrostatic charge of N95 masks is a major contributor to their filtration efficiency, improving it at least 10-fold over uncharged fabric” (Tsai et al., Journal of Electrostatics 2002; Peter Tsai, personal communication).

Prakash Lab COVID-19 Response Group Working Draft Document on N95 masks: https://docs.google.com/document/d/1aACcbkyZjR7nZy_wWeGQ9U2iGy0y4QajBeOL8RqAZIQ/edit

“Electrostatic charge contributes as much as 95% of the filtration efficiency”
Molina, A., Vyas, P., Khlystov, N., Kumar, S., Kothari, A., Deriso, D., … & Prakash, M. (2020). Project 1000 x 1000: Centrifugal melt spinning for distributed manufacturing of N95 filtering facepiece respirators. arXiv preprint arXiv:2004.13494. https://arxiv.org/pdf/2004.13494.pdf

Tsai, P. P., Schreuder-Gibson, H., & Gibson, P. (2002). Different electrostatic methods for making electret filters. Journal of electrostatics, 54(3-4), 333-341. https://www.researchgate.net/profile/Phillip_Gibson/publication/222659741_Different_electrostatic_methods_for_making_electret_filters/links/5a5912cba6fdcc3bfb5ab21e/Different-electrostatic-methods-for-making-electret-filters.pdf

History of Electrets

Jefimenko, O. D., & Walker, D. K. (1980). Electrets. The Physics Teacher, 18(9), 651-659. https://aapt.scitation.org/doi/abs/10.1119/1.2340651

Physics of Air Filtration

Hinds, W. C. (1999). Aerosol technology: properties, behavior, and measurement of airborne particles. John Wiley & Sons. https://www.wiley.com/en-us/Aerosol+Technology%3A+Properties%2C+Behavior%2C+and+Measurement+of+Airborne+Particles%2C+2nd+Edition-p-9780471194101

Scientific consortium for data-driven study of N95: https://www.n95decon.org/

N95 & virus particle sizes

Bałazy, A., Toivola, M., Adhikari, A., Sivasubramani, S. K., Reponen, T., & Grinshpun, S. A. (2006). Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks?. American journal of infection control, 34(2), 51-57. http://citeseerx.ist.psu.edu/viewdoc/download?doi=

Harnish, D. A., Heimbuch, B. K., Husband, M., Lumley, A. E., Kinney, K., Shaffer, R. E., & Wander, J. D. (2013). Challenge of N95 filtering facepiece respirators with viable H1N1 influenza aerosols. Infection Control & Hospital Epidemiology, 34(5), 494-499. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4646082/

Liao, L., Xiao, W., Zhao, M., Yu, X., Wang, H., Wang, Q., … & Cui, Y. (2020). “Can N95 respirators be reused after disinfection? How many times?. ACS nano. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7202248/

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