key: cord-1041283-odfne1fq
authors: Papavasiliou, Theodora; Chatzimichail, Stelios
title: A Customized 3D printed N95 Respirator Analogue To Face Crisis Capacity Scenarios in Pandemics such as the COVID-19 and to Support Surgical Personnel During PPE Shortages.
date: 2020-09-20
journal: J Plast Reconstr Aesthet Surg
DOI: 10.1016/j.bjps.2020.08.111
sha: 1a143201e7f0afe1e2e9d4f15f1fa7b548a64d80
doc_id: 1041283
cord_uid: odfne1fq

nan

The expansion of the global economy in the last century has been a wide enabler for rapid economic growth and technological development. It can however be said that this interwoven economic fabric has rendered most modern-day societies closely interdependent to one another, rendering them able to function normally only under a very delicate set of conditions. The ongoing COVID-19 pandemic has shown how extraordinary surges in patient morbidity and mortality can result in healthcare crises which manifest to severe economic, social and political disruptions. 1 During the ongoing pandemic, the shortage of Personal Protective Equipment (PPE) has been of alarming concern with medical professionals expressing concern with regards to shortage of surgical masks and N95 respirators. 2 For a respirator mask to work efficiently, the operator's respiration system has to be physically separated from the surrounding environment via a semi-permeable barrier. As such, air-tight sealing needs to be achieved in the application of this type of mask for it to work effectively. The current recommendation for PPE equipment for health care professionals is to use N95 class masks, defined as being able to retain particles of average size 300 nm at 95% or above retention rate. 3 In the last two month, the authors have noted the emergence of over 30 respiratory designs in various three dimensional (3D) printing repositories all of which fail to fulfill this requirement. 4 Currently adopted reusable respirators that fulfill the requirements are bulky and Plastic Surgeons are frequently faced with inability to use their loupes or other personal equipment with those, causing serious implications on the fluency of the surgical performance.

In our work, we employed 3D printing via Fusion Deposition Modelling (FDM) in order to create a rigid mask body and a filter protective cap (Figure1). We built upon the design by designing a 3D printed mold which would serve to imprint the contact points of the mask to the face of the operator. A silicone layer would be cast upon set mold and fitted to the mask serving as a sealing gasket. In order to achieve good contact of the mask to the silicone, the mold bears a 4.5 mm mid-plane indentation in order to fit tightly to the rigid mask body. The respirator design was performed using Computer Aided Design (CAD) and can be available in customized dimensions. Typical prints of the recommended respirator with the settings provided in Table 1 are obtained within three hours.

We chose to use segments from a 3M tie-on surgical mask for the semi-permeable filter. Previous studies have shown that such masks are able to block up to 96.4% of aerosolized Bacillus atrophaeus (diameter distribution: 925-1250 nm) and up to 89.5% of aerosolized MS2 Bacteriophage (mean diameter: 23 nm). 3 Despite the virus particle size being smaller than the pore size of the N95 or surgical mask filters, both are capable of blocking aerosols and performing at the prescribed rate. This is because filtering is achieved by several mechanisms in semi-permeable membranes. For instance, in HEPA filters which employ pore diameters of 300 nm, a NASA study on the 'Submicron and nanoparticulate matter removal by HEPA-rated media filters and packed beds of granular material' suggests that 99,5% of particles of 100 nm in size are filtered. 3 Based on the quantities of source material used we estimate the cost of mask production to be 2.267 GBP per mask. Provided the mold for the silicone parts is reusable however, PLA filament costs can be reduced for subsequent mask productions to 1.4 GBP per mask (Table 1) . We do however caution that if third parties are to use masks created by adopters that the necessary contamination control measures are taken, masks are sealed in sterile packaging and allowed to sit for the prescribed timeframe for the virus to be rendered inactive.

In summary, the recommended respirator is customized, ergonomic, reusable, has been validated by fit testing and is especially applicable for surgeons that require the use of loupes for their surgical technique, making it especially useful for Plastic Surgeons and microsurgeons. 5 Recognizing that inter-societal dependency is a oneway street, having a system in place able to rapidly respond and adapt to such spikes of high demand seems necessary. Recent technological advancements such as the advent of 3D printing, printed circuit boards as well as modular mechanical and biological parts have all been enablers to the rise of the 'citizen-led science' movement whereby individuals can make notable contributions to technology from the leisure of their own homes, no longer necessitating access to centralized facilities. In times of global crisis such as pandemics, this movement of individuals could potentially adapt and rise to the challenge in a manner resembling industry 4.0, whereby smart manufacturing of high demand goods can be spearheaded in a joint effort to aid to the cause. 

Disease Control Priorities: Improving Health and Reducing Poverty. Pandemic Impacts and Mitigation

Rational use of face masks in the COVID-19 pandemic

Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials

Copper 3D solution

Guidance on respiratory protective equipment (RPE) fit testing. Health and safety executive

Competing interests: None declared Funding: None Ethical approval: Not required, the corresponding author is shown in figure 1 therefore consent is not required.