A Simple Model Setup Using Spray-Drying Principles and Fluorescent Silica Nanoparticles to Evaluate the Efficiency of Facemask Materials in Terms of Virus Particle Retention.

Maximilian Oppmann,Benedikt Schug,Sarah Wenderoth,Karl Mandel,Thomas Ballweg

doi:10.1002/admt.202100235

Abstract

Herein, a simple model setup is presented to spray fine liquid droplets containing nanoparticles in an air stream transporting this toward a filter material. The nanoparticles are made of silica and tagged with a fluorescent dye in order to render the trace of the particles easily visible. The silica nanoparticles, in a first approximation, mimic virus (severe acute respiratory syndrome coronavirus 2) particles. The setup is used to evaluate different tissues, nowadays, in times of the coronavirus pandemic, commonly used as facemasks, with regard to their particle retention capability. The setup enables adjusting different “breathing scenarios” by adjusting the gas flow speed and, thereby, to compare the filter performance for these scenarios. The effective penetration of particles can be monitored via fluorescence intensity measurements and is visualized via scanning electron micrographs and photographs under UV light. Ultimately, a strong increase of particle penetration in various mask materials as function of flow speed of the droplets is observed and an ultimate retention is only observed for FFP3 and FFP2 masks.

Highlights

Introduction health authoritiesBefore the SARS-CoV-2 epidemic, two types of masks were predominant and represented the standard: theThe outbreak and worldwide spread of severe acute respiratory surgical masks and the filtering facepiece respirators syndrome coronavirus 2 (SARS-CoV-2) in 2020 revealed the vul- (FFR)
The modeling of breathing into a face mask with an artificial setup, in order to guarantee defined and reproducible measurements, comes with three challenges: first, fine droplets with solid particles inside need to be generated; second, an appropriate gas stream should take up these particles and guide them toward a tissue representing the mask material; and third, the filtered and the penetrated fractions of particles have to be collected (Figure 1, scheme a)
With the help of the downstream vacuum pump, the aerosol of silicate droplets is drawn through the membrane

Summary

Our Approach in Detail

Our concern was to develop the basics for a more realistic virus model, which in particular allows statements to be made about the actual spreading of viruses to better understand and control future pandemic events. With the suspension-based system, we achieve a more accurate and more realistic picture of what is happening than with a solution-based system, in which the substance to be analyzed is present as a solution or solid, depending on the external conditions. It is possible, in contrast to the FFP2 test protocol, to study the effect of aqueous aerosols and to realistically evaluate their retention capacity at the emitter side. Once the method has been established, which is shown in this current proof of principle study, it can be upgraded by adding state of the art aerosol generators and spectrometers in order to better control and study droplet size related effects

Results and Discussion

Conclusion

Experimental Section

Data Availability Statement