Washburn Equation Research Articles

Whipping Behavior of Rice Flour Dough

In this study, the bubbles in rice flour dough were investigated under a constant temperature. The bubble size distribution is important for the control of food texture. If bubble sizes depend mainly on the inertial force, viscous force, and surface tension, then the normalized mean bubble diameter should be a function of the Reynolds number and Weber number. We obtained experimental data using a hand mixer, and compared the properties of doughs prepared using six rice flours; each flour was prepared through a different milling process. We also added the size effect of the rice flour particles as the Bond number. Furthermore, we performed a dynamic wettability test to estimate the wettability of the rice flour surface. The results of this test were described well by the Washburn equation, and dccosθ was calculated as a wettability parameter (where, dc: effective diameter of a capillary in a powder bed, cosθ: the contact angle). The mean bubble diameter (dbm) generated by whipping was expected to be affected by the thickness (d) of the rod of the mixer, its movement speed, physical properties of the material, and gravitational acceleration. Therefore, dimensionless mean diameter (dbm/d) was expressed by a dimensionless equation. The empirical equation obtained was generally applicable to the variety of materials selected for this study.

Terahertz pulsed imaging as a new method for investigating the liquid transport kinetics of α-alumina powder compacts

Investigating the liquid transport kinetics of solid catalysts is of great importance for gaining a better understanding of the manufacturing and performance of such catalysts during reaction upon contact with the liquid. Terahertz pulsed imaging (TPI) coupled with a newly designed flow cell was used to quantify the rate of water ingress into α-alumina pellets with a range of different porosities. A wide range of compaction forces (cold compaction, 7–58kN) and sintering conditions (no firing and sintering at 1200 and 1300°C) was investigated to explore the optimal pellet microstructure, i.e. mechanically strong but sufficiently porous for fast liquid transport kinetics. The results confirm that both the microstructure characteristics, particularly porosity, as well as the surface properties, i.e. wettability, influence the liquid transport kinetics. Fitting the TPI penetration rates with a power law shows that the type of observed mass transport characteristics is consistent with Darcy flow. The Lucas–Washburn equation was used to calculate the hydraulic radius based on the transport data. In summary, the results demonstrate that TPI has great potential to study the liquid transport kinetics of porous ceramic catalysts and catalyst supports and that can comfortably quantify transport processes at rates of 250μms−1 and beyond in such substrates for better quality control and optimised design and performance of such materials.

Phenomenological analysis on whipping behavior of rice flour batter.

In this study, the bubbles in rice flour batter were investigated under a constant temperature, because the bubble size distribution is important for the control of food texture. We obtained experimental data using a hand mixer and compared the properties of doughs prepared using six rice flours; each flour was prepared through a different milling process. We also added the size effect of the rice flour particles as the Bond number. Furthermore, we performed a dynamic wettability test to estimate the wettability of the rice flour surface. The results of this test were described well by the Washburn equation, and dccosθ/dp was calculated as a wettability parameter (where, dc = effective diameter of a capillary in a powder bed, cosθ = the contact angle, dp = mean particle diameter of rice flour). If bubble sizes depend mainly on the inertial force, viscous force, surface tension, and gravity, then the normalized mean bubble diameter should be a function of the Reynolds number, Weber number, and Froude number. The mean bubble diameter (dbm) generated by whipping was expected to be affected by the thickness (d) of the rod of the mixer, its movement speed, and physical properties of the material. Therefore, dimensionless mean diameter (dbm/d) was expressed based on a dimensionless equation. In the three‐phase dispersion, different empirical equations were obtained depending on the amount of rice flour added, and the bubble diameter could be predicted using dimensionless parameters. In addition, the equations were generally applicable to the various materials selected for this study.Practical ApplicationThe powder properties of rice flour were investigated, and dimensionless parameters were analyzed to construct an appropriate process control system for rice flour‐based food products. Although the process method optimized for flour products is also used for rice flour products in practical situations, the comprehensive evaluation based on dimensionless parameters leads to optimization of the process for rice‐flour based products. Moreover, this optimization might strongly support the creation of a new texture, and thus, the potential for market expansion of rice‐flour based products is considerable.

Effect of gradient wettability on capillary imbibition in open semicircular copper channel

Open semicircular copper channels with a gradient wettability of 45°–3° or 3°–45° (contact angle of 1,2-propanediol), homogeneous wettability of 3°, and segmented wettability on their inner surfaces were constructed. The capillary imbibition of 1,2-propanediol in these channels demonstrates that, compared with the surface with homogeneous wettability, there are an additional driving force and resistance on the surfaces with a gradient wettability of 45°–3° and 3°–45°, respectively. Meanwhile, the channel with gradient wettability on the first half segment and homogeneous wettability on the second half segment could accelerate capillary imbibition better than that with gradient wettability on the whole channel. Furthermore, a smaller length ratio, i.e., length of gradient segment to that of homogeneous segment of the channel, demonstrates a better liquid acceleration effect. Based on the Lucas–Washburn equation, a theoretical model to describe capillary imbibition was established by introducing an additional force arisen from the positive gradient wettability and a retardation coefficient caused by the surface roughness. The flow front position vs flow time could be predicted by the established model in this work, and the relative error between the theoretical prediction and experimental result was less than 20.7%, indicating the rationality of the proposed model.

Demonstrating Aqueous-Phase Low-Molecular-Weight-Gel Wicking of Oil for the Remediation of Oil Spilled into Surface Water.

Oils spilled into surface water require effective and timely treatment. In this paper, we report on a low-molecular-weight gelator that can form gels in organic and aqueous phases. The aqueous gel was observed to absorb oils, which is proposed as a new class of materials for remediating oil spilled into surface water. The gels and the low-molecular-weight gelator have both fundamental and applied significance. Fundamentally, identifying the mechanisms that govern the formation of these gels and their resultant mechanical properties is of interest. Subsequently, these fundamental insights aid in the optimization of these gels for addressing spilled oil. First, we briefly compare the organic and aqueous gels qualitatively before focusing on the aqueous gel. Second, we demonstrate the ability of the aqueous gel to wick oils through experiments in a Hele-Shaw cell and compare our results to the Washburn equation for porous media. The Washburn equation is not entirely adequate in describing our results due to the change in volume of the porous media during the wicking process. Finally, we investigate mechanisms proposed to govern the formation of low-molecular-weight gels in the literature through rheological shear measurements during gel formation. Our experiments suggest that the proposed mechanisms are applicable to our aqueous gels, growing as anisotropic crystal networks with fractal dimensions between one and two dimensions from temporally sporadic nucleation sites.

Probing Ink-Powder Interactions during 3D Binder Jet Printing Using Time-Resolved X-ray Imaging.

Capillary-driven ink infiltration through a porous powder bed in three-dimensional (3D) binder jet printing (inkjet printing onto a powder bed) controls the printing resolution and as-printed “green” strength of the resulting object. However, a full understanding of the factors controlling the kinetics of the infiltration remains incomplete. Here, high-resolution in situ synchrotron radiography provides time-resolved imaging of the penetration of an aqueous solution of eythylene glycol through a porous alumina powder bed, used as a model system. A static drop-on-demand inkjet printer was used to dispense liquid droplets onto a powder surface. The subsequent migration of the liquid front and its interactions with powder particles were tracked using fast synchrotron X-radiography in the Diamond Synchrotron, with phase-contrast imaging at a frame rate of 500 Hz. Image processing and analysis reveal that both the time-dependent increment in the wetting area and the propagation of the “interface leading edge” exhibit heterogeneous behavior in both temporal and spatial domains. However, mean infiltration kinetics are shown to be consistent with existing infiltration models based on the Washburn equation modified to account for the spreading of the liquid drop on the powder surface and using a modified term for the bed porosity.

Transport characteristics of liquid-gas interface in a capillary membrane pore

Interface displacement of two phases mainly caused by replacement of one fluid with another one can occur inside the membrane pore during membrane preparation and characterization. This phenomenon is exemplified by measurement of liquid entry pressure (LEP) in membrane distillation, measurement of pore size and pore size distribution by the bubble point method, measurement of pore size and pore size distribution by porometry, wetting of dry membrane and also drying of wet membrane. In most of the theoretical studies, focus was on the transmembrane pressure required for one phase to enter into the membrane pores filled with another phase and little attention was paid to the movement of interface in the capillary. This paper attempts to discuss quantitatively the movement of interface, water/air interface in particular. Therefore, movement of interface was tracked using a well-founded model and consequently the pressure and velocity at the interface and the required time for replacement were studied. In addition, the influence of different parameters including pore radius, contact angle, and membrane thickness was assessed. It was found that the low resistance for the air flow, assumed in Washburn's equation, can be justified as an approximation. Moreover, the model proposed in this work can predict that the pressure at the water/air interface (when air replaces liquid water) may become significantly lower than the atmospheric pressure at the pore exit, causing pore shrinkage. As well, the pressure at the air/water interface (when liquid water replaces air) may become significantly higher than the feed pressure applied at the pore entrance, causing pore expansion.

Membrane gas-liquid contactor for tritium extraction from Pb-Li alloys

Abstract Gas-Liquid Contactors (GLC) have been studied for the extraction of tritium from Pb-Li blankets, typically consisting on bubble, packed or spray columns. Recent researches propose the use of Permeators-Against-Vacuum (PAV) in which dense metal membranes (V, Nb, Ta) are immersed into flowing Pb-Li: here the hydrogen isotopes pass through the membrane wall and are collected in the permeate side with help of vacuum. In this work, permeation behavior of a Membrane Gas-Liquid Contactor (MGLC) that combines both GLC and PAV concepts is presented. This device includes a porous ANSI 316 L stainless-steel membrane which is immersed into a Pb-Li alloy. Hydrogen isotopes are first absorbed into the liquid metal and then extracted through the membrane by vacuum pumping or purging with inert gas. In fact, the liquid metal penetrates the pores of the porous membrane then realizing a gas-liquid interface through which the hydrogen isotopes mass transfer takes place. The pore size of this membrane has been selected according to the Washburn equation so that the Pb-Li behaves as a “non-wetting liquid” and does not enter the vacuum/inert gas phase where leaks of liquid metal are not allowed. The study describes the preliminary design for the MGLC device working with a porous metal membrane and its experimental characterization at 340–370 °C and 270 kPa. A mass transfer model for the tritium extraction from Pb-Li is also presented, comparing both PAV and MGLC alternatives.

X-Ray computed tomography and traditional analysis of a capillary absorption test in cement pastes

Water absorption testing has the attraction of being simple, relatively quick and use water as a fluid which is the key substance in the possible concrete deterioration. However, in spite of the advantages its application has remained empirical, except for the testing of resistance to frost, through the identification of the critical degree of saturation. Rilem TC-116 studied this test, among others, for the characterization of concrete resistance against transport through the concrete pore network. Results indicated a low discriminating ability of the absorbency for qualifying concrete resistance and then, it seemed necessary to try to move forward by making the link between the absorption testing and the concrete pore microstructure. In the present work, thanks to the X-Ray computed tomography, it is described the evolution of the water front in three paste-specimen with different w/c ratios (different pore radius distributions). The observations allowed us to deduce that all the pores start to fill simultaneously, but the bigger ones fill quicker and rise less. The saturation degree is measured along the height of the sample, showing that each pore size has a different rate which becomes constant after the first hour. Washburn's equation was applied to the progressive advance of the water front, resulting in a pore radius much smaller than the one expected.

Dynamics of water imbibition through paper with swelling

We present a combined experimental and theoretical investigation of the dynamics of water imbibition through paper with swelling. The Washburn equation has been widely used to describe the dynamics of the liquid absorption in paper, but its prediction of liquid imbibition speed has been reported to be inaccurate. Our recent study (Chang et al., J. Fluid Mech., vol. 845, 2018, pp. 36–50) demonstrated that the internal cavity of cellulose fibres composing the paper is partially responsible for the limited accuracy of the Washburn equation based on oil imbibition experiments. Here we extend the investigation to water absorption through paper with swelling. We demonstrate that the swelling of the cellulose fibre network in addition to the internal voids of the cellulose fibres crucially affects the imbibition dynamics. Based on the microscopic observation that paper swelling is caused by the expansion of inter-fibre space, we suggest a mathematical model for water imbibition which considers both intra-fibre voids and swelling. By introducing parameters that characterize the swelling speed and volume of paper, our model markedly improves prediction of the water imbibition speed. The results provide not only a theoretical background for designing paper-based microfluidic systems, but also new insights into capillary flow through expandable porous media.

Enabling high rate capability, low internal resistance, and excellent cyclability for vanadium redox flow batteries utilizing ultrafast laser-structured graphite felt

The electrochemical performance of vanadium redox flow batteries (VRFBs) was enhanced via laser-patterned graphite felt (GF) electrodes. The laser-structured GF electrodes engineered via preparing a series of well-ordered microscopic channel structures with an average width of 200 μm, creating a three-dimensional carbon framework. The ultrafast laser patterning increased the porosity by 10%, as compared to pristine electrode. The analysis of the overpotential distribution using electrochemical impedance spectroscopy revealed that the electrode polarization involving charge transfer and diffusion resistance is strongly alleviated with the aid of carbon micro-perforation. The advanced design of laser-structured GF electrode also exhibits high rate capability, low internal resistance, and excellent cyclability. The improved performance was attributed to the synergistic effect involving (i) high electrochemically active surface area for rapid electrochemical reactions (i.e., V(II)/V(III) and V(IV)/V(V) redox couples) and (ii) excellent transport properties for facile electron/ion/species transport. The micro-scale channels created with the laser-ablation technique act as capillary structures and enabled homogeneous and rapid wetting of GF electrodes as formulated with the classical Washburn equation. The VRFB equipped with the laser-structured GF electrodes delivered a high discharge capacity with exceptional capacity retention upon extended cycling (>84.9%). Accordingly, the design of laser-structured electrode paves the pathway towards finely tuning the electrode internal microstructure for improved cyclability, durability, and capacity retention in various electrochemical energy storage/conversion devices (e.g. all-vanadium redox flow batteries).

Inverse modeling deduction of pore distribution in cement materials from capillary absorption features

The moisture transport performance of concrete is a vital factor that affects its durability, and this performance is closely related to the pore structures of the porous materials. In this study, water content profiles of capillary absorption were obtained using X-ray computed tomography technology. Based on the Lucas–Washburn equation, an inverse model was established to deduce the pore size distribution from the water content profiles. The feasibility of the proposed method was demonstrated using a size distribution model of the cement samples with different water-to-cement ratios. The obtained results were compared with the cumulative pore size distribution measured by mercury intrusion porosimetry, which indicated that the two methods exhibited satisfactory consistency.

A theoretical study on the capillary rise of non-Newtonian power-law fluids

The phenomena of capillary rise with the effect of displaced fluids are ubiquitous in both science and engineering, and the mathematical models and their analytical solutions of this problem have also received increasing attention. In this paper, a theoretical study on the rising dynamics of non-Newtonian power-law fluids in a capillary is performed, and the classical Lucas–Washburn equation is generalized to a nonlinear second-order differential equation in which the effects of the power-law index and displaced fluids are included. We analyze the imbibition behaviors of power-law fluids under the influence of displaced fluids in details, and also present some analytical solutions of different special cases and different time stages. The results show that for different special cases, it takes shorter time for shear thickening fluid to reach the equilibrium height. For different time stages, however, the rising phenomena of power-law fluids are more complex, and the average time for the shear-thinning fluid to reach the equilibrium height is longer compared to shear-thickening fluid, but an opposite phenomenon is observed for the case of μ1,0/μ2,0=100 (here μ1,0/μ2,0 is the viscosity ratio of two power-law fluids) in viscous time stage. In inertial time stages, the density ratio of the absorbed fluid to the displaced fluid also has a significant effect on the rising dynamics of imbibing fluid. Furthermore, the effect of dynamic contact angle is also included in the governing equation and analytical solutions. Through a comparison between the theoretical results and experimental data, a good agreement is observed. These results can be used as a priori for liquid absorption in industrial applications, including oil recovery, fuel cells and water collection of artificial silk.

Solution based freeze cast polymer derived ceramics for isothermal wicking - relationship between pore structure and imbibition

ABSTRACT Besides conventional applications for porous monoliths such as filtration, open porosity enables capillary transport. For this application, porous polymer-derived ceramic monoliths (SiOC) with different pore morphology and porosity were obtained by solution-based freeze casting. Methylpolysiloxane and (3-aminopropyl)triethoxysilane were used as a precursor and cross-linking agent, respectively. Tert-butyl alcohol and cyclohexane acted as solvents and created prismatic and dendritic pore morphology. Additionally, differences in solid loading and the addition of preceramic filler particles changed the open porosity from 62% to 79%, the mean pore window diameter from 11 µm to 21 µm and the isotropy. The lateral surface of the monoliths is mainly closed due to the use of a Si-coated film as an intermediate layer which prevents nucleation. Within the parameters characterizing the pore structure, open porosity and pore window diameter were found to be most influencing on wicking tested by the Washburn-Sorption method. The permeability was obtained by constant head experiments and from the viscous-dominated part of the wicking curve. Furthermore, predictions of wicking using the Lucas–Washburn equation with gravity effect which bases on the assumption of capillary bundles were conducted. Wicking experiments showed that describing a real porous structure by macroscopic parameters may not be sufficient for structures deviating strongly from the assumption of capillary bundles. The combination of prediction with the knowledge of main influencing factors allows for tailoring the pore structure of SiOC monoliths prepared by solution-based freeze casting for capillary transport applications.

Unidirectional solution-based freeze cast polymer-derived ceramics: influence of freezing conditions and templating solvent on capillary transport in isothermal wicking

Porous SiOC monoliths were prepared by solution-based freeze casting of polysiloxane at constant freezing temperature or constant freezing front velocity. Dendritic and prismatic pore structures were obtained by using cyclohexane and tert-butyl alcohol as solvent, respectively. Gradients in freezing velocity lead to gradients in pore window size, whereas a constant freezing velocity (3.3–6.8 µm/s) generates homogeneous pore structures. The water permeability varies from 1.12 × 10−13 to 1.03 × 10−11 m2 and correlates with the pore window diameter (10–59 µm) and the porosity (51–82%). In wicking tests, the gradient in pore window size is clearly reflected by a pronounced decrease in the wicking speed. Contrary, a homogeneous pore structure results in wicking curves which are closer to the prediction according to the Lucas–Washburn equation. However, this theoretical approach based on the three parameters, pore window size, porosity and permeability, is insufficient to describe complex three-dimensional pore structures. Besides the porosity, the pore morphology was found to be a major influencing factor on the wicking. The filling of secondary dendrites slows down the wicking into the dendritic structure. Fastest wicking was observed for a prismatic pore structure at low freezing front velocity (6.6 µm/s) and high porosity (78%), whereas slowest wicking occurred into the dendritic structure with high porosity (76%) and constant freezing temperature (− 20 °C). The knowledge of the relationship between structural properties and the resulting wicking behavior can address a variety of pivotal applications in chemical engineering for capillary transport.

Filler materials to prevent polymer intrusion into mesoporous substrates during thin film formation

Abstract The versatility and ease of synthesis of polymers have made membrane separations an attractive option for treatment of complex waters. However, most water-permeable polymers lack tolerance to corrosive environments. In our laboratory, we are developing a new class of composite membranes that incorporate water-permeable molecular sieve particles within an impermeable polymer matrix in a thin film on a porous support membrane. Together these water-selective molecular sieve particles and impermeable polymers potentially enable superior chemical resistance to harsh environments, such as extreme pH or oxidative chemicals, when compared to membranes cast using water-permeable polymers. However, using an impermeable polymer presents a unique challenge in a membrane design; if the impermeable polymer intrudes into the pores of the support material, it will block water transport through the support membrane. In this paper, we report the results of filling the pores of the support material with a liquid that is immiscible with the impermeable polymer casting solution in order to limit polymer intrusion into the support during casting. We developed a model and procedure for selecting liquid filler materials, based on a modified Washburn equation, which can be broadly applied to any solvent-polymer-support combination. Specifically, we report on the balance between the gravitational and capillary forces necessary to select a filler material that limits polymer intrusion into the support.

Influence of surface characteristics on the penetration rate of electrolytes into model cells for lithium ion batteries

Filling of cells with liquid electrolytes is the time-determining step in the production of lithium-ion batteries (LIBs). The influencing factors are not completely understood and need further research. The adhesion of the solid components, i.e. anode, cathode and separators, to the electrolyte and the respective interfaces play an important role. In this study, the penetration of liquid electrolytes is monitored by a combination of tensiometry and chronoamperometry. A setup including all battery components is proposed as model for battery cells. Diethyl carbonate is employed as model for the electrolyte. The penetration rates of the liquid into a stepwise extended model setup (separator; anode; cathode; separator/anode; separator/cathode; and anode/separator/cathode) in confined geometry between glass plates are determined with reproducible results. A modified Washburn equation combining surface tensions of liquid and solids forming the interface, and complex geometries of separators and electrodes is used to develop the penetration model. Comparative measurements in a glove box yield comparable results with the real electrolyte solution. The penetration of the model electrolyte into ceramic-coated separators is significantly faster than into polyolefin separators due to higher surface roughness and higher polarity of ceramic-coated separators. The wetting times obtained by chronoamperometric measurements correlate with the tensiometric penetration rates. The higher the tensiometric penetration rate, the lower is the chronoamperometric wetting time. The results of the study contribute to a deeper understanding of the interactions between electrolyte and solid components in LIBs and provide a new method to pre-evaluate battery components.

An alternative method to evaluate the surface free energy of mineral fillers based on the generalized Washburn equation

This paper presents a new method to measure surface free energy of the mineral fillers. This method takes the generalized Washburn equation as theoretical basis. First, the mineral fillers are conditioned to form a duplex liquid film by saturated reference liquid vapors. The resultant effective capillary radius of the mineral fillers is then measured through the column wicking test of the conditioned mineral fillers using the reference liquid as test probe. After that, three independent liquids are selected to measure their spreading pressures on the mineral fillers based on their column wicking test results along with the measured resultant effective capillary radius. Finally, an equation set based on the Good-van Oss-Chaudhury model is established to compute the surface free energy of the mineral fillers. The newly developed method has been successfully applied to measure the surface free energy for four different types of mineral fillers. Distribution of the three surface energy components and range of the total surface free energy of the selected mineral fillers have been found to be consistent with those reported in literature for the particle aggregates with similar mineralogical composition. Besides, insignificant variation has been identified in each surface energy component of the mineral fillers measured from the new method and from the two references methods. In these regards, this new method can be used as an alternative for accurately measuring the surface free energy of the mineral fillers with simple test technique and high efficiency.

A novel method for measuring surface free energy of highly wettable mineral powders

This paper develops a novel method to measure the surface free energy for the highly wettable mineral powders by means of the capillary rise measurements. In this method, a generalized modified Washburn equation is first derived to capture the spreading wetting mechanism of the probe liquid into the mineral powders with high wettability. A series of apolar liquids are then selected to conduct the capillary rise test to generate a plot of the measured test results against the square root of the liquid surface tension. Fitting such a plot with a parabolic function, the resultant effective capillary radius and the powder apolar surface energy component can be solved. Then the spreading pressure of two independent liquids is calculated from their capillary rise test results. The polar acid and polar base surface energy components of the highly wettable powders can be finally determined by substituting the calculated spreading pressure values into the Good-van Oss-Chaudhury model. The proposed method has been successfully applied to measure the surface free energy for four typical types of mineral powders. The measured surface free energies of the selected powders are found to be approximately the same as those obtained from a previous method with different principle. In this regard, the proposed method is validated to be capable of accurately measuring the surface free energy for highly wettable mineral powders.

Controlling Macroscopic Phase Separation of Aqueous Two-Phase Polymer Systems in Porous Media.

In previous work, our group discovered a phenomenon in which a mixed polymer-salt or mixed micellar aqueous two-phase system (ATPS) separates into its two constituent phases as it flows within paper. While these ATPSs worked well in their respective studies to concentrate the target biomarker and improve the sensitivity of the lateral-flow immunoassay, different ATPSs can be advantageous for new applications based on factors such as biomarker partitioning or biochemical compatibility between ATPS and sample components. However, since the mechanism of phase separation in porous media is not completely understood, introducing other ATPSs to paper is an unpredictable process that relies on trial and error experiments. This is especially true for polymer-polymer ATPSs in which the characteristics of the two phases appear quite similar. Therefore, our group aimed to develop semiquantitative guidelines for choosing ATPSs that can phase separate in paper. In this work, we evaluated the Washburn equation and its parameters as a potential mathematical framework to describe the flow behavior of polymer-salt and micellar ATPSs in fiberglass paper. We compared bulk phase fluid characteristics and identified the viscosity difference between the phases as a key determinant of the potential for phase separation in paper. We then used this parameter to predict the phase separation capabilities of polyethylene glycol (PEG)-dextran ATPSs in paper and control the composition of the leading and lagging phases. We also, for the first time, successfully demonstrated the phase separation phenomenon in hydrogels, thereby extending its application and potential benefits to an alternative porous medium.