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X-ray fluorescence and photoelectron spectroscopies help test face mask materials

29 October 2021 | News
by Ian Michael

In a study that used inorganic, physical and analytical chemistry to mimic respiratory droplets that can carry viruses, researchers demonstrated a mechanism that enables multiple mask materials to be protective. Led by Professor Amy Marschilok of Stony Brook University, the study findings suggest that adsorptivity of mask materials is an important feature in providing protection from viruses such as SARS-CoV-2.

Studies evaluating dry measurements of particles to test mask breakthrough have been conducted during the 2020/21 pandemic. In contrast, researchers in this investigation used a novel method that involved creating a virus nanoparticle mimic, using functionalised nanoparticles suspended in artificial saliva, then spraying the suspension and providing scientists with a unique wet characterisation approach to compare the effectiveness of potential mask materials. Thus, rather than viewing the mask as a simple screen, the study tests the adsorptive properties of the mask materials for trapping virus in saliva droplets.

“We recognised the precious nature of the N95 respirators, and therefore decided to compare mask materials that are broadly available and represented a range of technology and manufacturing readiness using the evaluation methodology that we developed”, said Marschilok.

The masks ranged from a commercialised N95 product, to a commercially available mask material and a potential future mask material prepared by Oak Ridge National Laboratory’s Carbon Fiber Technology Facility. Each material was characterised using a variety of methods including scanning electron microscopy and X-ray photoelectron spectroscopy at BNL’s Center for Functional Nanomaterials (CFN).

Wetting properties of the mask materials were quantified by measurements of the contact angle with an artificial saliva. The surface functionalised metal oxide nanoparticle suspension in artificial saliva was sprayed with an airbrush device through the mask material onto a target. The amount of suspension reaching the target was measured using X-ray fluorescence spectroscopy at BNL’s National Synchrotron Light Source-II (NSLS-II).

“Our goal was to develop new approaches to characterise mask materials, investigate the adsorptive properties of the mask and consider dispersion of droplets containing the virus. The mechanism investigated adsorbing or trapping the suspended virus mimic rather than blocking it”, summarised Marschilok.

Marschilok and colleagues found that multiple types of mask materials functioned effectively under the test conditions. When the researchers conducted the same experiments to a target without the use of mask protection even at longer distances, much less protection occurred from the viral particles than in the presence of mask materials—a result that further points toward the protective value of masks against virus exposure.

The authors say further investigation is necessary to determine the stability of mask materials over time and extended use as a protection against viral particles.

Read the original journal paper in Applied Materials & Interfaces

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