A smartphone microscopic method for rapid screening of cloth facemask fabrics during pandemics

Abstract

Background In pandemics, because of increased demand and subsequent shortage of commercial facemasks, people need to use cloth facemasks, although such masks are reported to provide reduced protection. These masks can be prepared in local levels from different fabric materials. In developing countries, cloth masks are preferable because of low cost and added advantages of reusability. The filtering performance of a cloth facemask depends on the facial fit and on the material properties of fabrics such as porosity, yarn spacing or packing, and pore size. In resource limited settings, an affordable and easy to implement method that can assess the surface properties of cloth facemask fabrics would be important. Methods In this work, we developed a smartphone microscopic method for rapid screening of fabric quality. We measured the field of view of the microscope and as a proof of concept, we implemented the method to examine surfaces of sixteen locally available cloth mask fabrics. Results Out of the 16 masks examined, we found very diverse yarn packing and pore morphology (pore size and shape) in the fabrics. The pore size ranged from ~80 to 720 μm; much larger than respiratory droplet and bio-aerosol. This observation partly explains why such cloth facemasks provide reduced protection to the user during pandemics. The performance of a cloth facemask partly depends on the material properties of fabric such as yarn packing, pore size, porosity. Therefore, the surface properties of fabrics obtained from the smartphone method can be used to get preliminary idea on the facemask quality. We believe that the method can be an affordable and rapid method for selection of better fabrics for cloth facemask during pandemics.

Face masks against COVID-19: Standards, efficacy, testing and decontamination methods

“…Neupane et al have developed an optical microscopy setup, using a $20 sapphire ball lens, a smartphone camera, a machine shop aluminum plate, and a white LED. [ 76 , 77 ] This device was capable of rapidly screening face mask fabrics to determine the pore size of cloth masks, where a smaller pore size implied a higher PFE. Thus, it is implicitly assumed that the masks tested do not use electrostatic filtration and are not suitable for electret masks.…”

“…[ 49 ] After repeated wash-dry cycles, cloth masks should be disposed since their PFE decreases due to surface stretching, which enlarges pore sizes. [ 76 , 77 ]…”

Cellulose‐based micro‐fibrous materials imaged with a home‐built smartphone microscope

“…B. Neupane, Chaudhary, & Sharma, 2020) with some modification. The optical setup of the microscope is shown in Figure 1.…”

Advances in Facemasks during the COVID-19 Pandemic Era

“…Bright patches and dark regions are the pores and the yarns, respectively. Reproduced with permission from ref ( 123 ). Copyright 2020 PeerJ.…”

“…Although filtration was not investigated, the authors postulate that there may be a correlation with particle penetration ( Figure 5 c). 123 …”