Multiphysics approach for fluid flow and charge transport in paper-based mi- crofluidics

FRANCK, NICOLÁS; BERLI, CLAUDIO L. A.; URTEAGA, RAÚL; KLER, PABLO A.

Congreso; III Brazil-Argentine Microfluidics Congress - VI Congreso de Microfluídica Argentina; 2022

A multiphysic model that simultaneously describe different transport phenomena in paper sub-strates is presented. The paper is modelled as a bundle of periodically constricted tubes, whosepore radius distribution is described by a probability density function (PDF). We present the math-ematical basis and the experimental validation of such model. Two different materials frequentlyused in paper-based microfluidics were used: Whatman #1 and Muntktell 00A filter papers. Thesesubstrates were studied by: (i) hydrostatic pressure-driven flow, (ii) capillary imbibition, and, (iii)electrical resistance measurements. Three different PDFs were considered to represent the outputof these experiments, and the quality of the model-based predictions were objectively evaluatedby using a Chi-Square test. The model was able to simultaneously describe the three transportphenomena by using the log-normal PDF with two statistical parameters: mean and variance. Theformulation avoids including the tortuosity of the flow path, which is commonly employed as anadjusting parameter. The multiphysics model was also successfully used to calculate the parametersof single-physics models, such as Darcy’s permeability and Lucas-Washburn diffusion coefficient.