Evaporation versus imbibition in a porous medium

Engeland, Charlotte Van; Haut, Benoı̂t; Spreutels, Laurent; Sobac, Benjamin

doi:10.1016/j.jcis.2020.02.105

Cited by 19 publications

(6 citation statements)

References 65 publications

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“…The sweat channel width ( w c ) is another important parameter for sweat collection, as it determines the travel rate of the sweat. Although Darcy’s law, Lucas-Washburn equation [ 38 ], Modifications to Darcy’s law and LW equation [ 39 ], Richards equation [ 40 ], and flow simulation or visualization tools [ 41 ] can approximately calculate the micro-fluid flow behavior in paper material, fluid imbibition into paper is a complex process governed by a highly coupled system of length and time-scaled parameters. Therefore, the sweat channel width in filter paper is typically determined by experiment, traditionally called a trial-and-error strategy.…”

Section: Resultsmentioning

confidence: 99%

A One-Dollar, Disposable, Paper-Based Microfluidic Chip for Real-Time Monitoring of Sweat Rate

Wang

et al. 2022

Micromachines

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Collecting sweat and monitoring its rate is important for determining body condition and further sweat analyses, as this provides vital information about physiologic status and fitness level and could become an alternative to invasive blood tests in the future. Presented here is a one-dollar, disposable, paper-based microfluidic chip for real-time monitoring of sweat rate. The chip, pasted on any part of the skin surface, consists of a skin adhesive layer, sweat-proof layer, sweat-sensing layer, and scale layer with a disk-shape from bottom to top. The sweat-sensing layer has an impressed wax micro-channel containing pre-added chromogenic agent to show displacement by sweat, and the sweat volume can be read directly by scale lines without any electronic elements. The diameter and thickness of the complete chip are 25 mm and 0.3 mm, respectively, permitting good flexibility and compactness with the skin surface. Tests of sweat flow rate monitoring on the left forearm, forehead, and nape of the neck of volunteers doing running exercise were conducted. Average sweat rate on left forearm (1156 g·m−2·h−1) was much lower than that on the forehead (1710 g·m−2·h−1) and greater than that on the nape of the neck (998 g·m−2·h−1), in good agreement with rates measured using existing common commercial sweat collectors. The chip, as a very low-cost and convenient wearable device, has wide application prospects in real-time monitoring of sweat loss by body builders, athletes, firefighters, etc., or for further sweat analyses.

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Section: Resultsmentioning

confidence: 99%

A One-Dollar, Disposable, Paper-Based Microfluidic Chip for Real-Time Monitoring of Sweat Rate

Wang

et al. 2022

Micromachines

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“…Capillary transport has been considered by many authors, both without [52][53][54] and with [55][56][57] evaporation. Its effect is to redistribute a solute deposited on a dry substrate.…”

Section: Advection-dispersion Equationsmentioning

confidence: 99%

Solvent-pumped evaporation concentration on paper in linear and radial geometries

Syms,

Wright

2023

Biomicrofluidics

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Solvent-pumped evaporation-driven concentration of an initial distribution of solutes on a porous substrate is considered in one and two dimensions. Approximate analytic solutions to the isotropic advection–dispersion equations are first found for a Gaussian kernel and an infinite domain, following the smoothed particle approximation. Analytic solutions for more general initial distributions are then found as sums of Gaussians, and comparison is made with numerical solutions. In each case, initial distributions are advected toward the stagnation point and concentrated. Two-dimensional analysis is then extended to describe anisotropy in permeability and diffusion, and hydrodynamic dispersion. Radial-flow experiments are performed using filter papers and water-soluble dyes. Diffusion coefficients, temperature and humidity profiles, and the evolution of spot distributions are measured. The results confirm minor anisotropy in permeability and diffusion, limited hydrodynamic dispersion, and largely uniform evaporation. Péclet numbers over 2500 are demonstrated. Evaporation-driven concentration provides a mechanism for solute transport over long timescales. Potential applications lie in the design of paper spray microanalytical devices operating by solvent pumping rather than capillary flow.

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“…In the analytical models, different external effects are considered separately. Van Engeland et al 35 have shown the simultaneous effects of capillary, gravity, and evaporation on liquid imbibition through porous media. However, in all practical applications, capillary action, evaporation, swelling, barrier effects, and gravitational effects all work together to cause a liquid to rise through a porous medium.…”

Section: ■ Introductionmentioning

confidence: 99%

Imbibition of Liquids through a Paper Substrate in a Controlled Environment

Mahapatra

2022

Langmuir

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Liquid spreading on open surfaces is a widely observed phenomenon. The physics of liquid spreading has become more complex when the surface is porous like paper or fabrics due to the evaporation of the liquid and swelling of the fibers. In this study, we have performed liquid imbibition experiments on paper strips in a controlled environment with and without using hydrophobic boundaries. The experimental results are compared to the existing analytical models that account for each effect separately. The existing models were found to be inaccurate in predicting the experimental results. We developed new analytical models by modifying existing models to predict the capillary rise of the liquid through the paper substrate accurately. Different effects, such as the barrier (hydrophobic boundary), evaporation, and swelling, are considered simultaneously while developing the modified models to mimic the exact practical situation for the first time. We discovered that the modified models predict the experimental results more accurately than the existing models. For cases with and without barriers, the final models considering several effects simultaneously predict the data with a maximum error range of 7 and 10%, respectively. Finally, we conducted capillary rise experiments with volatile (water) and non-volatile (silicon oil) liquids at various temperatures and under various relative humidity conditions to validate the analytical results.

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Evaporation versus imbibition in a porous medium

Cited by 19 publications

References 65 publications

A One-Dollar, Disposable, Paper-Based Microfluidic Chip for Real-Time Monitoring of Sweat Rate

A One-Dollar, Disposable, Paper-Based Microfluidic Chip for Real-Time Monitoring of Sweat Rate

Solvent-pumped evaporation concentration on paper in linear and radial geometries

Imbibition of Liquids through a Paper Substrate in a Controlled Environment

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