RAPID: Current and Next Generation Mask Elastomer Straps: Mechanical Integrity with Sterilization and Reuse

This COVID-19 Rapid Response Research (RAPID) grant will investigate how sterilization and reuse strategies for personal protective equipment used by healthcare workers affect the properties of mask straps. Single use N95 and other masks are in short supply in the US and globally, which has stimulated interest in their sterilization and reuse. In addition to the sterilization procedure killing viruses, it is important that the mask retains a known fraction of functionality including mechanical durability over multiple sterilizations. Sterilization treatments have the possibility of degrading mask materials, in particular elastic straps, which have been identified as a weak link in initial studies. This project will contribute to this important, global need by studying the effects of various sterilization treatments on the structure and properties of strap materials to ensure safe and reliable fitting of masks that will be reused a limited number of times prior to disposal. Additionally, there will be a need for technology developed in this project in low to middle income countries that transcends the immediate crisis and will impact emergency care situations world-wide for years to come.

The goal of this work is to correlate the type and extent of sterilization treatment with the properties of the elastomeric straps. To accomplish this, materials characterization experiments will be performed that establish links between changes in material structure and properties to the combined effects of the sterilization method used and the mechanical deformation associated with donning and doffing. Specifically, chemical changes will be evaluated using thermal and spectroscopic methods that quantify the extent and the spatial distribution of the changes as a function of exposure dose and time. Complementary testing of viscoelastic and mechanical properties will evaluate changes in performance because of sterilization. Beyond characterization of the straps, the integrity of the attachment to the mask will be measured using mechanical testing. The results of this work will provide a more complete understanding of strap degradation for each sterilization method, thereby informing the design of sterilization processes and mask components to optimize the effective mask lifetime. Furthermore, should this work conclude that strap integrity is the limiting factor in the lifetime of a given N95 mask, understanding these underlying failure mechanisms will provide insight into the development of feasible material alternatives or modifications that can be made to extend overall mask lifetime.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.