All research gathered by JenniferMaker, the designer of the pattern I use.

Cambridge University Study in Smart Air article: What Are the Best Materials for Making DIY Masks?

CDC: Improve the Fit and Filtration of Your Mask to Reduce the Spread of COVID-19

Wake Forest Baptist Medical Center: Testing Shows Type of Cloth Used in Homemade Masks Makes a Difference, Doctors Say

Face Masks Against COVID-19: An Evidence Review

DIY Face Mask Filter Materials: What to Use & What to Avoid