Browsing by Author "Franck, Nicolás"

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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;
    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.
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    Precise electroosmotic flow measurements on paper substrates
    (2021-01-12) Franck, Nicolás; Schaumburg, Federico; Urteaga, Raúl; Kler, Pablo A.
    A novel method for electroosmotic flow (EOF) measurement on paper substrates is presented; it is based on dynamic mass measurements by simply using an analytical balance. This technique provides a more reliable alternative to other EOF measurement methods on porous media. The proposed method is used to increase the amount and quality of the available information about physical parameters that characterize fluid flow on microfluidic paper–based analytical devices (µPADs). Measurements were performed on some of the most frequently used materials for µPADs, i.e. Whatman #1 , S&S and Muntktell 00A filter paper. Obtained experimental results are consistent with the few previously reported data, either experimental or numerical, characterizing EOF in paper substrates. Moreover, a thorough analysis is presented for the quantification of the different effects that affect the measurements such as Joule effect and evaporation. Experimental results enabled, for the first time, to establish well defined electroosmotic characteristics for the three substrates in terms of the magnitude of EOF as funtion of pH, enabling researchers to make a rational choice of the substrate depending on the electrophoretic technique to be implemented. The measurement method can be described as robust, reliable, and affordable enough for being adopted by researchers and companies devoted to electrophoretic µPADs and related technologies.