INVESTIGADORES
URTEAGA Raul
congresos y reuniones científicas
Título:
Capillary filling of multilayered porous silicon measured by optical coherence tomography
Autor/es:
MARCELO SALLESE; JORGE TORGA; ENEAS MOREL; NICOLAS BUDINI; URTEAGA, RAÚL
Lugar:
Córdoba
Reunión:
Congreso; II Brazil - Argentine Microfluidics Congress V Congreso de Microfluídica Argentina; 2019
Resumen:
Capillary driven flow is important for many scientific and engineering applications, from oil recovery, geological CO2 sequestration or contaminant transport in aquifers to design of textile fabrics or the development of lateral flow assays based on paper microfluidics. The imbibition of a wetting fluid in a homogeneous porous medium follows the diffusion-like behavior described by Washburn [1]. In a two-layered porous medium (i.e. two stacked porous layers with different porosities) the imbibition of a wetting fluid due to capillary action has been previously described to consist of two fronts that depend on how both layers are interconnected at the interface [2]. The determination of capillary filling dynamics in nanoporous structures and, in particular, of the filling fraction profile along the wet front has been proposed as a possible method for characterizing the pore-size distribution of the structure [3]. In this work we propose a method to determine the capillary filling dynamics of multilayered porous silicon (PS) films by optical coherence tomography (OCT). When the liquid enters the PS structure there is an increase in the optical thickness of the layer. Using a single-arm interferometer with appropriate motorized stage with stepper motors it is possible to determine the optical thickness of the sample as a function of position and time, which allows monitoring the capillary filling dynamics in real time. The interference signal is generated by reflections at the different interfaces of the sample with a reference reflection (Fig. 1 Left). From the analysis of this signal it is possible to measure the optical path traveled by the light beam through the sample and independently determine the filling fraction of each single porous layer. Ethyl alcohol was used for capillary imbibition of PS samples, whose pores were sealed at the top with a thermoplastic film to allow capillary imbibition to take place transverse to the pores (Fig. 1 Right). The results obtained indicate that the filling dynamics follow a Washburn type behavior in both layers but with a greater diffusivity in the layer of smaller pore-size (Fig. 1 Right). These results were analyzed using an interconnected pore model that allows obtaining information on the morphology of the individual layers on the sample.