  We propose a theoretical model to elucidate intermolecular electrostatic
interactions between a virus and a substrate. Our model treats the virus as a
homogeneous particle having surface charge and the polymer fiber of the
respirator as a charged plane. Electric potentials surrounding the virus and
fiber are influenced by the surface charge distribution of the virus. We use
Poisson-Boltzmann equations to calculate electric potentials. Then, Derjaguin's
approximation and a linear superposition of the potential function are extended
to determine the electrostatic force. In this work, we apply this model for
coronavirus or SARS-CoV-2 case and numerical results quantitatively agree with
prior simulation. We find that the influence of fiber's potential on the
surface charge of the virus is important and is considered in interaction
calculations to obtain better accuracy. The electrostatic interaction
significantly decays with increasing separation distance, and this curve
becomes steeper when adding more salt. Although the interaction force increases
with heating, one can observe the repulsive-attractive transition when the
environment is acidic.
