| Physicists at the Laboratoire de Physique des Solides (CNRS / Université Paris-Saclay) have developed a method to measure the thickness of thin liquid films down to just a few nanometers. By combining multiple analysis strategies tailored to different thickness regimes with an open-source tool, this approach enables precise and reproducible monitoring of liquid film thinning. |
Measuring the thickness of thin liquid films is a central challenge in soft matter and interface physics, with applications ranging from foams and emulsions to functional coatings. These films evolve significantly over time, with their thickness continuously decreasing from several micrometers down to a few nanometers before rupture. This wide range of thicknesses makes experimental characterization particularly challenging.
Researchers at the Laboratoire de Physique des Solides (Université Paris-Saclay, CNRS), in collaboration with ESPCI Paris – PSL, have developed a white-light interferometry method capable of measuring the thickness of non-opaque films over a very broad range, down to a few nanometers. The method relies on analyzing the spectrum of light reflected by the film, which exhibits interference fringes whose number and position depend directly on the film thickness.
The researchers identified three typical experimental situations. When the film is relatively thick, the periodicity of the fringes is analyzed using a Fast Fourier Transform (FFT). For intermediate thicknesses, a detailed analysis of the positions of spectral maxima and minima provides accurate thickness measurements. Finally, when the film becomes very thin and only a few fringes remain, a renormalization method inspired by Scheludko’s work allows the correct interference order to be identified and enables measurements below the micrometer scale.
All these approaches are implemented in an open-source Python library, optifik, which automates the analysis and ensures reproducibility. Applied to foam films, this method enables real-time monitoring of thinning down to a few nanometers. More broadly, it is applicable to any non-opaque thin film and represents a powerful tool for studying interface dynamics.
Contributors:
Victor Ziapkoff, François Boulogne, Anniina Salonen, Emmanuelle Rio
Teams / Laboratories:
- Laboratoire de Physique des Solides (Université Paris-Saclay, CNRS)
- ESPCI Paris – PSL, CNRS, Sorbonne Université
Financements :
Agence Nationale de la Recherche (ANR – 22-CE06-0029)
Références :
Ziapkoff, V., Boulogne, F., Salonen, A. and Rio, E. (2026), White light interferometry analysis for measuring thin film thickness down to a few nanometers, The European Physical Journal E, 49, 4. https://doi.org/10.1140/epje/s10189-025-00545-9
Contact :
Emmanuelle Rio – emmanuelle.rio@universite-paris-saclay.fr