The use of nanoporous structures with known morphology allows studying the properties of fluids in conditions of strong spatial confinement. Alternatively, the capillary filling of nanoporous structures with simple fluids provides information on their morphology. When a liquid enters the porous structure there is an increase in the optical path of the porous layer, and measuring this optical path as a function of position and time allows evaluating the filling dynamics of the pores. In this work, we determined the capillary filling dynamics of nanostructured porous silicon (PS) by optical coherence tomography. The high spatial resolution of this technique allows one not only to follow the position of the liquid front as a function of time but also to resolve in detail the filling fraction profile of the liquid front inside the PS matrix. Moreover, these profiles contain information about the pore size distribution in the PS structure. Therefore, we show how the determination and analysis of the filling fraction profile along the advancing liquid front can be used as a method to study the pore size distribution inside PS structures.

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We report the implementation of lensless off-axis digital holographic microscopy as a non-destructive optical analyzer for nano-scale structures. The measurement capacity of the system was validated by analyzing the topography of a metallic grid with ≈ 150 n m thick opaque features. In addition, an experimental configuration of self-reference was included to study the dynamics of the capillary filling phenomena in nanostructured porous silicon. The fluid front position as a function of time was extracted from the holograms, and the typical square root of time kinematics was recovered. The results shown are in agreement with previous works on capillary imbibition in similar structures and confirm a first step towards unifying holographic methods with fluid dynamics theory to develop a spatially resolved capillary tomography system for nanoporous materials characterization.

La Fundación Gutenberg, a través del Instituto Argentino de Artes Gráficas, y el Grupo de Fotónica Aplicada de la Facultad Regional Delta, de la Universidad Tecnológica Nacional, se asociaron para trabajar en conjunto en el desarrollo de una nueva técnica óptica para ser aplicada en la caracterización de materiales impresos. En este marco, se llevó adelante un proyecto de desarrollo tecnológico y social (PDTS) que se orientó a la aplicación de la tomografía de coherencia óptica, para la caracterización de tintas y recubrimientos, sobre diferentes sustratos flexibles, principalmente polímeros tipo PET y cartulina, de productos impresos mediante flexografía. Se presentan a continuación la introducción al tema y la motivación para generar este trabajo colaborativo, como así también la descripción de la técnica utilizada y los resultados obtenidos hasta el momento. Finalmente, se presentan las conclusiones con las perspectivas del desarrollo propuesto y los trabajos a futuro.