Change of sign in the Casimir interaction of peptide films deposited on a dielectric substrate

Abstract

The Casimir free energy and pressure of thin peptide films deposited on a dielectric substrate are investigated in the region of parameters where they change their sign. Numerical computations are performed for a modelled peptide film on a silica glass plate. The Casimir free energy is computed at room temperature as a function of the film thickness and the fraction of water contained in the film. It is shown that the values of the Casimir pressure change from negative to positive when the film thickness decreases to below some value in the region from 115 to 133 nm depending on the fraction of water in the film. Possible applications of the obtained results to the problem of stability of peptide coatings are discussed.