Effects of the buffer layer on the Casimir pressure of peptide films deposited on a substrate

The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales. In this work, the Casimir pressure of peptide films deposited on a layered substrate is investigated. Three types of semi-infinite substrates, i.e., silica, silicon and gold, are considered. The buffer layer between the peptide film and substrate consists of silicon or silica. The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm, depending on the thickness of the buffer layer and the substrate. The results suggest that the critical thickness of peptide films for Casimir equilibrium increases (or decreases) by increasing the thickness of the silicon (or silica) buffer film. The influences of wetting and electrolyte screening on the Casimir pressure are also investigated. Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics.