  Understanding the interactions between viruses and surfaces or interfaces is
important, as they provide the principles underpinning the cleaning and
disinfection of contaminated surfaces. Yet, the physics of such interactions is
currently poorly understood. For instance, there are longstanding experimental
observations suggesting that the presence of air-water interfaces can
generically inactivate and kill viruses, yet the mechanism underlying this
phenomenon remains unknown. Here we use theory and simulations to show that
electrostatics provides one such mechanism, and that this is very general.
Thus, we predict that the free energy of an RNA virus should increase by
several thousands of $k_BT$ as the virion breaches an air-water interface. We
also show that the fate of a virus approaching a generic liquid-liquid
interface depends strongly on the detailed balance between interfacial and
electrostatic forces, which can be tuned, for instance, by choosing different
media to contact a virus-laden respiratory droplet. We propose that these
results can be used to design effective strategies for surface disinfection.
Intriguingly, tunability requires electrostatic and interfacial forces to scale
similarly with viral size, which naturally occurs when charges are arranged in
a double-shell distribution as in RNA viruses like influenza and all
coronaviruses.
