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Mass Customization of Respiratory Protective Equipment
There are statistically significant differences between laser sintering, and post-processing techniques on the
the Young and the Senior groups for RMSE Euclidean surface finish of the mask/face contact area, and Young’s
distance, and between the Asian and Others, Healthy Modulus, biocompatibility and sterilizability of the print
and Obese, Young and Middle-age, and Young and materials. Different filter materials with different levels
Senior for Maximum Euclidean distance. Nonetheless, of particle filtration capabilities can also be evaluated to
all differences in their absolute values (Table 2) were Filter materials, with different levels of particle filtration
<1 mm. The Maximum Euclidean distance is 1.7 mm – capabilities, can also be investigated to determine their
2.3 mm for each of these groups, which are significantly performance and impact on custom fitted masks.
smaller than the 6 mm gap reported in similar commercial
masks . With a much smaller gap to fill, users can 4. Conclusions
[78]
potentially apply less strap pressure onto the mask to This study presented a fully automated design pipeline
create a good seal, reducing chances of skin trauma. to enable MC of RPE via AM. The pipeline was
This study may be under-powered as the current validated against 205 facial scans to generate custom
sample is skewed towards male, White, and high BMI fit respirator mask CAD models. The pipeline achieved
populations, whereas the sample size for female, non- 96% processing success rate with <2 min/scan processing
White and normal BMI populations were small. Future time. When virtually fitted, the mean RMSE and
studies should look to collect a more evenly distributed Maximum Euclidean distance between the masks and
gender, BMI and ethnicity sample with a larger sample faces were 0.62 mm and 2.03 mm, respectively. It was
size to further validate the universality of this pipeline. found that there was no statistically significant difference
Nonetheless, initial results show great potential to in goodness of fit between different age, gender, ethnicity,
produce customized RPE products that can fit equally and BMI subgroups. When combined with appropriate
well across different demographic and demographic AM processes and materials, it could be a promising
subgroups. This contrasts current anthropometric sizing route towards the true MC of RPE or even other body-
methodologies which contain inherent biases due to the fitted products.
sample populations they were cased on.
The proposed pipeline was deployed as an online Acknowledgments
application which promoted decentralized manufacturing The authors would like to thank Lara Lewington and the
during the period when there was a global shortage of RPE. team from the BBC, and Kristie Lu Stout from the CNN,
However, the pipeline’s main contribution is to quickly for featuring this study - the Mensura Mask project. These
create custom-fitted RPE models that offer superior fit media exposures have greatly helped us with volunteer
to commercial masks, making it a viable tool to produce recruitment around world so that we can build a dataset
RPE products in the healthcare and construction industry with better demographic distribution. The authors would
where good fit and comfort are required. This pipeline can also like to thank Mike Westlake from the Autodesk for
be deployed quickly in the extent of future pandemics. connecting us with the CNN. Finally, the authors would
The pipeline was validated computationally to like to thank all volunteers who have participated in this
demonstrate that it is possible to rapidly produce RPE study.
design models that fit well to a user’s face. The pipeline
offers a route to lower product unit costs by automating Funding
the design phase, thus removing that barrier for mass
customizing wearables. It also shows a novel and This work was funded by Community Jameel and Imperial
promising design methodology that is not inherently College London under the award of the Community
biased towards specific demographic group as it is in the Jameel Imperial College COVID-19 Excellence Fund,
traditional anthropometric sizing approach. The mask and the Imperial College President’s PhD Scholarship
model presented in this pipeline had been shown to be Fund.
successfully fabricated through the stereolithography Conflicts of interest
(SLA) process in our previous study , taking an average
[65]
of 8 h and using 40 mL of resin to fabricate the mask The authors declare no conflict of interest.
body. A fit test study is currently being conducted to
evaluate the performance of the 3D printed custom-fitted References
masks against commercial masks. Future studies can 1. Lan J, Song Z, Miao Z, et al., 2020, Skin Damage among
build upon our previous and current work to investigate
other factors affecting the manufacturing of the mask, Health Care Workers Managing Coronavirus Disease-2019.
including the impact of different AM build processes, J Am Acad Dermatol, 82:1215-6.
such as SLA, fused deposition modeling and selective 2. Gefen A, Alves P, Ciprandi G, et al., 2020, Device-related

130 International Journal of Bioprinting (2021)–Volume 7, Issue 4