Effects of surface characteristics on the wetting /drying of artificial saliva and antiviral performance

Abstract

The COVID-19 pandemic has heightened the global concern regarding the transmission of pathogens via respiratory droplets deposited on surfaces. It is a critical need to better understand the fate of respiratory droplets on common surfaces to facilitate better strategies against pathogen transmission. In this study, we investigated the wetting and drying behaviours of artificial saliva on polyethylene terephthalate (PET) substrates with varied surface characteristics, and their corresponding antiviral properties. Surface morphology of the PET films, acquired by Atomic Force Microscopy (AFM), shows that the increased roughness is attributed to the inclusion of inorganic particles within the polyester layer underneath the coating layer. The surface free energy is governed by the PET surface coating chemistry instead of surface geometry according to the contact angle measurement. The wetting behaviour of the artificial saliva shows that strong polarity was found to correlate with an enhanced saliva adhesion. An increased concentration of mucin could improve its wetting on hydrophobic PET surfaces. The drying behaviour of the saliva indicates that droplet phase separation appears on the low surface energy surfaces. The asperities present on the PET surfaces could disrupt the potential nucleation and crystallization processes of the saliva droplets. However, viable virus was detected on all PET surfaces for at least 16 h in the splash virucidal test. The results suggest that, as non-porous materials, PET films are unable to inhibit viral infectivity through surface modifications in surface roughness and free energy. Therefore, the incorporation of antimicrobial additives appears necessary to achieve antiviral performance.