Nondestructive high-throughput screening of nanopore geometry in porous membranes by imbibition

CENCHA, LUISA G.; FLOUDAS, GEORGE; URTEAGA, RAÚL; HUBER, PATRICK; STEINHART, MARTIN; KAPPL, MICHAEL; BERLI, CLAUDIO L. A.

Córdoba

Congreso; II Brazil - Argentine Microfluidics Congress V Congreso de Microfluídica Argentina; 2019

Synthetic nanoporous media, in particular monolithic porous membranes, play an increasing scientific and technological role. However, their characterization in terms of pore size and pore homogeneity is still an extremely demanding experimental task, which in most cases involves the sample destruction. Here we show that a method based on capillarity-driven imbibition together with a fluid dynamic model enable a precise determination of the pore geometry as a function of the distance across the membrane. The model accounts for the imbibition into closed-end, axisymmetric pores having diameters that change as function of the pore depth. We demonstrate that taking into account for geometry- and air compression-induced deviations from classical Lucas-Washburn dynamics precisely describes the imbibition dynamics. The model was validated by laser interferometry experiments with sub-millisecond temporal resolution. Imbibition of three simple liquids (isopropanol, ethanol, and hexane) into self-ordered anodic alumina membranes containing arrays of parallel closed-end nanopores characterized by a slight conicity was studied. It is shown that the model provides an improved description of nanoscale fluid dynamics and then geometric characterization of nanoporous membranes with simple liquids becomes possible. These results are a sound base for future rheological studies of confined complex liquids, where confinement-induced effects influencing filling dynamics need to be discriminated from effects related to pore geometry and air