Three-dimensional characterization of nanoporous membranes by capillary filling using high speed interferometry

A high-speed interferometric system was developed to analyze nanostructured porous silicon (PS) membranes by measuring reflectance variations during capillary filling from both sides. A high-speed camera was employed to capture the reflectance evolution of the entire sample area with the necessary temporal resolution, providing quantitative information on filling dynamics. By integrating these data with a simple fluid dynamic model, it is possible to examine the internal structure of the membranes and determine the effective pore radii profiles along their thickness. The system is capable of accurately measuring radii within the range of 10-20 nm, with a spatial resolution of ∼20 μm and an in-depth resolution of ≈1μm. This three-dimensional characterization provides valuable insights into the complex morphology of PS membranes and can be applied to other nanostructured porous materials.