Efficient Reduction of Casimir Forces by Self-Assembled Bio-Molecular Thin Films

Casimir forces arise if the spectrum of electromagnetic fluctuations are restricted by boundaries. There is great interest both in fundamental science and technical applications to better understand and technically control these forces. In this work, the influence of five different self-assembled bio and organic monolayer thin films on the Casimir force between a plate and a sphere is experimentally investigated. It is found that the films, despite being a mere few nanometers thick, reduce the Casimir force by up to 14%. Spectroscopic data indicate a broad absorption band whose presence can be attributed to the mixing of electronic states of the underlying gold layer and those of the molecular film due to charge rearrangement. Using Lifshitz theory, it is calculated that the observed change in the Casimir force is consistent with the measured change in the effective dielectric properties. The nanometer-sized molecules can penetrate small cavities, and cover any surface with high efficiency. This process seems compatible with current methods in the production of micro-electromechanical systems (MEMS), which cannot be miniaturized beyond a certain size due to ‘stiction’ caused by the Casimir effect. This approach can therefore offer a practical solution for this problem.