Fluctuation-induced free energy of thin peptide films

Abstract

We apply the Lifshitz theory of dispersion forces to find a contribution to the free energy of peptide films which is caused by the zero-point and thermal fluctuations of the electromagnetic field. For this purpose, using available information about the imaginary parts of dielectric permittivity of peptides, the analytic representation for permittivity of typical peptide along the imaginary frequency axis is devised. Numerical computations of the fluctuation-induced free energy are performed at room temperature for the freestanding peptide films, containing different fractions of water, and for similar films deposited on dielectric (SiO${}_2$) and metal (Au) substrates. It is shown that the free energy of a freestanding peptide film is negative and, thus, contributes to its stability. The magnitude of the free energy increases with increasing fraction of water and decreases with increasing thickness of a film. For peptide films deposited on a dielectric substrate the free energy is nonmonotonous. It is negative for thicker than 100 nm films, reaches the maximum value at some film thickness, but vanishes and changes its sign for thinner than 100 nm films. The fluctuation-induced free energy of peptide films deposited on metallic substrate is found to be positive which makes films less stable. In all three cases, simple analytic expressions for the free energy of sufficiently thick films are found. The obtained results may be useful to attain film stability in the next generation of organic microdevices with further shrinked dimensions.

arXiv comment20 pages, 7 figures, 1 table; accepted for publication in Phys. Rev. E

References in corpus (16)

• The Casimir force between real materials: experiment and theory
• Isoelectronic determination of the thermal Casimir force
• Demonstration of the Casimir force between ferromagnetic surfaces of a Ni-coated sphere and a Ni-coated plate
• Investigation of the Casimir interaction between two magnetic metals in comparison with nonmagnetic test bodies
• Measurement of the gradient of the Casimir force between a nonmagnetic sphere and a magnetic plate
• Reduction of the Casimir force from indium tin oxide film by UV treatment
• Comment on "On the temperature dependence of the Casimir effect"
• Modifying the Casimir force between indium tin oxide film and Au sphere
• Observability of thermal effects in the Casimir interaction from graphene-coated substrates
• Low-temperature behavior of the Casimir free energy and entropy of metallic films
• Casimir free energy of dielectric films: Classical limit, low-temperature behavior and control
• Casimir free energy of metallic films: Discriminating between Drude and plasma model approaches
• Casimir free energy and pressure for magnetic metal films
• Effective interactions between fluid membranes
• The van der Waals and Casimir energy of anisotropic atomically thin metallic films
• Characteristic properties of the Casimir free energy for metal films deposited on metallic plates

Cited by in corpus (5)

• Effect of increased stability of peptide-based coatings in the Casimir regime via nanoparticle doping
• Casimir pressure in peptide films on metallic substrates: Change of sign via graphene coating
• Fluctuation-induced dispersion forces on thin DNA films
• Attractive and repulsive fluctuation-induced pressure in peptide films deposited on semiconductor substrates
• The Casimir free energy of peptide films on a silicon substrate: Impact of dielectric-to-metal transition in silicon and nanoparticles in peptide