Browsing by Author "Berli, Claudio L. A."

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    Comprehensive model of electromigrative transport in microfluidic paper based analytical devices
    (2020-01-06) Schaumburg, Federico; Kler, Pablo A.; Berli, Claudio L. A.
    A complete mathematical model for electromigration in paper-based analytical devices is derived, based on differential equations describing the motion of fluids by pressure sources and EOF, the transport of charged chemical species and the electric potential distribution. The porous medium created by the cellulose fibers is considered like a network of tortuous capillaries and represented by macroscopic parameters following an effective medium approach. The equations are obtained starting from their open-channel counterparts, applying scaling laws and, where necessary, including additional terms. With this approach, effective parameters are derived, describing diffusion, mobility and conductivity for porous media. While the foundations of these phenomena can be found in previous reports, here, all the contributions are analyzed systematically and provided in a comprehensive way. Moreover, a novel electrophoretically driven dispersive transport mechanism in porous materials is proposed. Results of the numerical implementation of the mathematical model are compared with experimental data, showing good agreement and supporting the validity of the proposed model. Finally, the model succeeds in simulating a challenging case of free-flow electrophoresis in paper, involving capillary flow and electrophoretic transport developed in a 2D geometry.
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    Multiphysics approach for fluid and charge transport in paper-based microfluidics
    (2022-10-08) Franck, Nicolás; Berli, Claudio L. A.; Kler, Pablo A.; Urteaga, Raúl; Franck, N. et al. Multiphysics approach for fluid and charge transport in paper-based microfluidics. Microfluidics and Nanofluidics, Vol. 26: article number 87 (2022).
    A multiphysic model that simultaneously describe different transport phenomena in porous media is presented. The porous matrix is regarded as a bundle of periodically constricted tubes, whose pore radius distribution is described by a probability density function (PDF). The mathematical basis and the experimental validation of the model are reported. Two different materials frequently used in paper-based microfluidics were used: Whatman #1 and Muntktell 00A filter papers. These substrates were studied by capillary imbibition, hydrostatic pressure-driven flow, and electrical resistance measurements. Different PDFs were evaluated to represent the output of these experiments, and their predictions were quantified by using a Chi-Square test. The model was able to simultaneously describe the three transport phenomena by using the log-normal PDF with two statistical parameters: mean and variance. The formulation avoids including the tortuosity of the flow path, which is commonly employed as an adjusting parameter. The multiphysics model was also successfully used to calculate the parameters of single-physics models, such as Darcy’s permeability and Lucas-Washburn diffusion coefficient. Furthermore, after obtaining a suitable PDF, the proposed model can be applied to different porous materials, as well as to the design of complex paper-based microfluidic devices that combine several types of papers.