Validity of Capillary Imbibition Models in Paper-Based Microfluidic Applications

Gerlero, Gabriel S.; Valdez, Andrés; Urteaga, Raúl; Kler, Pablo A.

doi:10.1007/s11242-021-01724-w

Cited by 6 publications

(10 citation statements)

References 54 publications

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“…The BCM, which was developed initially to account for the imbibition of water in reservoir rocks and soil, , has largely remained unexplored in the context of paper-based microfluidic transport. However, recent studies have applied and verified BCM for paper-based liquid transport systems. , The Brooks–Corey framework approaches the transport modeling by considering a two-phase transport model, where the liquid (water) is driven through a porous network of paper containing either air or water. Additionally, the model also considers a range of pore sizes in the paper substrate by considering a pore size distribution index (λ p )an intrinsic property of the porous media .…”

Section: Methodsmentioning

confidence: 99%

“…The Brooks and Corey’s model (BCM) is one such model that can be applied with two-phase Darcy’s law to capture imbibition dynamics and has been successfully applied to capture fluid flow dynamics in partially saturated soil systems . Other models like the Van Genuchten (VG) model , and the LET family of models , can also be used to calculate the capillary pressure. The major difference between these models and the BCM is that the BCM considers a distinct entry capillary pressure head of the non-wetting fluid (air) as one of the model parameters resulting in expressing the saturation pressure with the entry capillary pressure head.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Relative Humidity and Paper Geometry on the Imbibition Dynamics and Reactions in Lateral Flow Assays

et al. 2022

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Lateral flow assays and paper microfluidics have the potential to replace benchtop instrumented medical diagnostic systems with instrument-free systems that rely on passive transport of liquid through micro-porous paper substrates. Predicting the imbibition dynamics of liquid through dry paper substrates is mostly modeled through the Lucas−Washburn (LW) equations. However, the LW framework assumes that the fluid front exhibits a sharp boundary between the dry and wet phases across the liquid imbibition interface. Additionally, the relative humidity in the environment results in moisture trapped within the pores of the paper substrates as the paper attains an equilibrium with the ambient air. Here, we apply a two-phase transport framework based on Brooks and Corey's model to capture imbibition dynamics on partially saturated paper substrates. The model is experimentally validated and is then used to predict the liquid−paper imbibition dynamics in simulated environments with 1−70% relative humidity. The model was also used to determine the saturation gradient of liquid along the imbibition interface of the paper substrate. Insights from these studies enabled us to determine the mechanism of the liquid transport in partially saturated porous paper substrates. The model also enabled us to evaluate the optimal paper shapes and relative humidity of the environment that maximize imbibition rates and minimize imbibition front broadening. Finally, we evaluate the effect of moisture content of paper on the rate of paper-based biochemical reaction by amplifying a sequence of the SARS-CoV-2 RNA target via reverse transcriptase loop-mediated isothermal amplification. Taken together, this study provides some important guidelines to academic and applied researchers working in point-of-care diagnostics to develop paper-based testing platforms that are capable of functioning in a robust manner across multiple environmental conditions.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Relative Humidity and Paper Geometry on the Imbibition Dynamics and Reactions in Lateral Flow Assays

et al. 2022

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“…Widely adopted constitutive relations for capillary flow are those by Brooks and Corey (1964) and Van Genuchten (1980)-implementations of which are already included in the packages-along with more recently developed models such as the LET correlations (Lomeland, 2018). Also included as part of the packages is the implementation of the novel LETd model for capillary flow, which is a LET-based simplification specially targeted for paper-based microfluidic applications (Gerlero et al, 2022b). The mathematical expressions of these models are covered in the Supplementary Material.…”

Section: Governing Equation and Boltzmann Transformationmentioning

confidence: 99%

“…In many applications, knowing the diffusive flux is also of interest. In a problem of capillary flow, the diffusive flux measures the Darcy velocity of the fluid; as such, the diffusive flux q can be used as input for solving transport problems (Gerlero et al, 2022b). This quantity can be recovered as:…”

Section: Reconstructing the Solutionmentioning

confidence: 99%

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Open-source high-performance software packages for direct and inverse solving of horizontal capillary flow

Gerlero

Kler

2023

Capillarity

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This work introduces Fronts, a set of open-source numerical software packages for nonlinear horizontal capillary-driven flow problems in unsaturated porous media governed by the Richards equation. The software uses the Boltzmann transformation to solve such problems in semi-infinite domains. The scheme adopted by Fronts allows it to be faster and easier to use than other tools, and provide continuous functions for all involved fields. The software is capable of solving problems that appear in hydrology, but also in other particular domains of interest such as paper-based microfluidics. As the first known open-source implementation to adopt this approach, Fronts has been validated against analytical solutions as well as existing software achieving remarkable results in terms of computational costs and numerical precision, and is meant to aid the study and modeling of capillary flow. Fronts can be freely downloaded and installed, and offers a friendly environment for new users with its complete documentation and tutorial cases.

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A simple method for the assessment of electrophoretic mobility in porous media

Franck,

Vera Candioti,

Gerlero

et al. 2023

Electrophoresis

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Developing paper‐based electrophoretic methods involve dealing with significant uncertainty levels when compared to their capillary counterparts. Critical information for developing these kinds of methods are the electrophoretic mobility of background electrolytes and samples. This work presents the design and characterization of a device for measuring the electrophoretic mobilities of dyes in porous media. The device was developed with the aim of validating a previously presented model and also proposing a protocol for the straightforward determination of electrophoretic mobilities in porous media when open‐channel values are already known. Whatman #1 paper was used as a model substrate as far as it is the most common porous medium substrate for paper‐based electrophoresis. The device was designed using a numerical simulation–assisted approach, utilizing OpenFOAM® and specific solvers for capillary transport and electromigration, namely porousMicroTransport and electroMicroTransport, respectively. The electrophoretic mobilities of five dyes were analyzed experimentally with the proposed device. To establish appropriate comparative values at different pHs, experiments in fused silica capillaries were also performed. An effective parameter model for describing the electrophoretic behavior of dyes in porous media, that is, the constriction factor, was found consistent with previous reports for the Whatman #1 paper. This consistency was found after considering (via direct measurements) the chromatographic effect of the medium over each dye. Consequently, the recorded values hold significant worth due to their potential for direct application in designing new experiments or devices in Whatman #1 paper. With the validation of the model through the experiments with the proposed device, those researchers interested on developing electrophoretic methods in porous substrates can make use of the open‐channel electrophoretic mobilities reported in the literature, or in the well‐known software databases, and correct them for the media of interest just by performing two simple characterization steps.

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Validity of Capillary Imbibition Models in Paper-Based Microfluidic Applications

Cited by 6 publications

References 54 publications

Effects of Relative Humidity and Paper Geometry on the Imbibition Dynamics and Reactions in Lateral Flow Assays

Effects of Relative Humidity and Paper Geometry on the Imbibition Dynamics and Reactions in Lateral Flow Assays

Open-source high-performance software packages for direct and inverse solving of horizontal capillary flow

A simple method for the assessment of electrophoretic mobility in porous media

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