Guideline for Coronavirus Innovation: Face masks
Co-Created with the help of Patricia Sosa
Welcome dear innovator, this is a time where all inventions are welcome, appreciated and all media of change and help is going to make a difference in the world. I want to use some gathered data to provide you with a brief summary and general guidelines that you can consider when developing a device or solution from a biomedical point of view. In this small article, we will start with a brief description of the “coronavirus” virus and why considering the size of your inventions its important, particularly for facial masks.
What is a “Coronavirus”
There are a lot of coronaviruses out there, they can be transmitted to and by animals or how they are scientifically called, zoonotic [1]. What is important at the time is the name of the type of coronavirus that is triggering the pandemic. It is the SARS-CoV-2 and it causes the COVID-19 sickness. As we all appreciate a good summary, a “Data sheet” for non-experts will be provided.
SARS-CoV-2 Data Sheet*
Ways of transmission: Corporal fluid droplets and fecal shedding (basically all that comes out of someone’s body) [5]
Size: 60 to 140 nm [2] but its usually associated with 5 µm aerosols (super tiny droplets of basically all that comes out of someone’s body ) [6]
Lives on plastics: 72 hours or more [3]
Lives on stainless steel: 36–72 hours [3]
Lives on cardboard: 24 hours [3]
Lives on cooper: 4 hours [3]
Lives on cotton cloths: 12–24 hours [4]
Lives on wood: 12–24 hours [4]
Lives on the air: 3 hours [4]
Ways of destruction (inactivation):
Acetone (after 5 minutes in solution) [4]
10% Formaldehyde and Paraformaldehyde (after 5 minutes in solution) [4]
10% Clorox (after 5 minutes in solution) [4]
75% ethanol (after 5 minutes in solution) [4]
2% phenol (after 5 minutes in solution) [4]
*We will be adding more info on our datasheet in the next few days.
Size matters
As viewed on the COVID data sheet the virus size is nanometric. When designing, consider your material porosity, your machine’s minimum layer resolution, or the need of special filters. Remember this particularly when designing or creating and using Personal Protective Equipment (PPE). For you to have a small idea, we gathered typical minimum layer resolutions for some 3D printers as it is important for you to consider.
Face Masks
If you were wondering why n95 masks were so important (for people exposed to high risk zones) now you know that the SARS-CoV-2 has a nanometric size. N95 respirators can protect against particles as small as 0.3 microns according to FDA [7] and according to Lam, Tu-Ngoc & Wu (cool scientists) and quoting “The fiber diameter and porosity strongly affect filtration performance” [8].
Regarding other fabric masks, as you saw in the provided data sheet, The virus can live on cotton for no longer than one day and sterilization is simple and won’t harm the material. It is important to know that the penetration of nanoparticles in different fabric masks goes from 40–90% [9]. According to the study called: “Testing the Efficacy of Homemade Masks: Protect in an Influenza Pandemic?” Using a fabric homemade mask will not protect a healthcare professional exposed to the virus, but it reduces the amount of aerosol particles expelled by sick patients [10].
In conclusion, if you printed or are considering making 3D printed masks, make sure that the porosity of the material fulfills the requirements of protection and use the minimal resolution in your printer. Remember that the virus can live in plastic for 3 days or more, therefore you have to consider a material that can be sterilized.
The best use of 3D printed masks is as a barrier for you and people that might be infected (for them not to spared small particles on saliva or mucus) but it is not recommended for healthcare personnel attending sick patients unless the penetrability of the printed mask is proven to be effective for the size of aerosols.
If you are considering on creating a cloth mask, remember that the usage of these masks it is not recommended for healthcare personnel attending sick patients, But it will help reduce the spreading of the virus. When creating a mask, make sure to either use a pattern provided by healthcare officials. Or make sure that your pattern completely covers nose and mouth and that the accommodation of the mask has no open spaces between the mask and the skin.
PD: if you find a material that can repel the virus, be printed or electrospun that will be cool, and novel and it might just save us all since porosity might be reconsidered.
PD2: Avoid using n95 masks if you are not at super high risk and exposure. Let them be used by healthcare professionals.
References
[1] Ou, X., Liu, Y., Lei, X. et al. Characterization of spike glycoprotein of SARS-CoV-2 on virus entry and its immune cross-reactivity with SARS-CoV. Nat Commun 11, 1620 (2020). https://doi.org/10.1038/s41467-020-15562-9
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[3] Doremalen N, Bushmaker T, Morris D, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. DOI: 10.1056/NEJMc2004973
[4] First Data on Stability and Resistance Of Sars Coronavirus Compiled By Members Of Who Laboratory Network https://www.who.int/csr/sars/survival_2003_05_04/en/
[5] Ong SWX, Tan YK, Chia PY, et al. Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient. JAMA. Published online March 04, 2020. doi:10.1001/jama.2020.3227
[6] Judson, S. D., & Munster, V. J. (2019). Nosocomial Transmission of Emerging Viruses via Aerosol-Generating Medical Procedures. Viruses, 11(10), 940. https://doi.org/10.3390/v11100940
[7] N95 Respirators and Surgical Masks (face Masks) Center for Devices and Radiological Health — https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/n95-respirators-and-surgical-masks-face-masks
[8] Lam, Tu-Ngoc & Wu, Chen-Hsien & Huang, Sheng-Hsiu & Ko, Wen-Ching & Huang, Yu-Lih & Ma, Chia-Yin & Wang, Chun-Chieh & Huang, E-Wen. (2019). Multi-Scale Microstructure Investigation for a PM2.5 Air-Filter Efficiency Study of Non-Woven Polypropylene. Quantum Beam Science. 3. 20. 10.3390/qubs3040020.
[9] Samy Rengasamy, Benjamin Eimer, Ronald E. Shaffer, Simple Respiratory Protection — Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles, The Annals of Occupational Hygiene, Volume 54, Issue 7, October 2010, Pages 789–798, https://doi.org/10.1093/annhyg/meq044
[10] Davies, Anna & Thompson, Katy-Anne & Giri, Karthika & Kafatos, George & Walker, James & Bennett, Allan. (2013). Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?. Disaster medicine and public health preparedness. 7. 413–418. 10.1017/dmp.2013.43.
