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Le Dizès Castell R, Mirzahossein E, Grzelka M, Jabbari-Farouji S, Bonn D, Shahidzadeh N. Visualization of the Sol-Gel Transition in Porous Networks Using Fluorescent Viscosity-Sensitive Probes. J Phys Chem Lett 2024; 15:628-635. [PMID: 38205957 PMCID: PMC10801688 DOI: 10.1021/acs.jpclett.3c02634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 11/21/2023] [Accepted: 12/01/2023] [Indexed: 01/12/2024]
Abstract
The sol-gel transition involves the transformation of a colloidal suspension into a system-spanning, interconnected gel. This process is widely used to reinforce mechanically weakened porous artifacts, such as sculptures but the impact of the restricted geometry (porous network) on the gelation dynamics of the solution remains unclear. Here, using fluorescent viscosity-sensitive molecular rotors, confocal microscopy, and model pores, we visualize the local viscosity changes at the microscale that accompany the sol-gel transition of a methyltriethoxysilane solution into a gel network. We show that, with evaporation of the solvent, a viscosity gradient develops near the free surface, triggering the sol-gel transition inside small pores near the surface. In homogeneous porous media, this leads to skin formation, which reduces the evaporation rate. In heterogeneous porous media, a gradient in gel density develops toward the heart of the porous material, where the gel formation mainly occurs as capillary bridges within smaller pores.
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Affiliation(s)
| | - Elham Mirzahossein
- Institute
of Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
| | - Marion Grzelka
- Laboratoire
Léon Brillouin, Université Paris-Saclay, CEA-Saclay, 91191 Gif-sur-Yvette
Cedex, France
| | - Sara Jabbari-Farouji
- Institute
of Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
| | - Daniel Bonn
- Institute
of Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
| | - Noushine Shahidzadeh
- Institute
of Physics, University of Amsterdam, Amsterdam 1098XH, The Netherlands
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Le Dizès Castell R, Prat M, Jabbari Farouji S, Shahidzadeh N. Is Unidirectional Drying in a Round Capillary Always Diffusive? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5462-5468. [PMID: 37024431 PMCID: PMC10116593 DOI: 10.1021/acs.langmuir.3c00169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/29/2023] [Indexed: 06/19/2023]
Abstract
The unidirectional drying of water in cylindrical capillaries has been described since the discovery of Stefan's solution as a vapor diffusion-controlled process with a square root of time kinetics. Here we show that this well-known process actually depends on the way the capillary is closed. Experiments are performed on the evaporation of water in capillaries closed at one end with a solid material or connected to a fluid reservoir. While we recover Stefan's solution in the first case, we show that in the second situation the water plug evaporates at a constant rate with the water-air meniscus remaining pinned at the exit where evaporation proceeds. The presence of the liquid reservoir closing the capillary combined with a capillary pumping effect induces a flow of the water plug toward the evaporation front leading to a constant-rate drying, substantially faster than the prediction of Stefan's equation. Our results show that a transition from a constant-rate evaporation regime at short times to a diffusion-driven evaporation regime at long times can be observed by increasing the viscosity of the fluid in the reservoir blocking the other end of the capillary. Such transition can also be observed by connecting the capillary end to a solidifying fluid like epoxy glue.
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Affiliation(s)
| | - Marc Prat
- Institut
de Mécanique des Fluides de Toulouse (IMFT), Université
de Toulouse, 31400 Toulouse, France
| | - Sara Jabbari Farouji
- Institute
of Physics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Noushine Shahidzadeh
- Institute
of Physics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
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Fischer R, Schoeller J, Rossi RM, Derome D, Carmeliet J. Wicking fingering in electrospun membranes. SOFT MATTER 2022; 18:5662-5675. [PMID: 35861313 DOI: 10.1039/d2sm00472k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Pronounced fingering of the waterfront is observed for in-plane wicking in thin, aligned electrospun fibrous membranes. We hypothesize that a perturbation in capillary pressure triggers the onset of fingering, which grows in a non-local manner based on the waterfront gradient. Vertical and horizontal wicking in thin electrospun membranes of poly(ethylene-co-vinyl alcohol) (EVOH) fibers with varying fiber alignment and degree of orientation is studied with backlight photography. A non-local transport model considering the gradient of the waterfront is developed, where fiber orientation is modeled with a correlated random field. The model shows that a transition from straight to highly fingered waterfront occurs during water uptake as observed in the experiment. The size and shape of the fingers depend on fiber orientation. Based on good model agreement, we show that, during wicking in thin electrospun membranes, fingering is initially triggered by a perturbation in capillary pressure caused by the underlying anisotropic and heterogeneous membrane structure which grows in a non-local manner depending on the waterfront gradient.
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Affiliation(s)
- Robert Fischer
- Laboratory of Multiscale Studies in Building Physics, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland.
- Laboratory for Biomimetic Membranes and Textiles, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
- Chair of Building Physics, Swiss Federal Institute of Technology Zürich (ETHZ), Stefano-Franscini-Platz 5, 8093 Zürich, Switzerland
| | - Jean Schoeller
- Laboratory for Biomimetic Membranes and Textiles, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
- Department of Health Science and Technology, Swiss Federal Institute of Technology Zürich (ETHZ), Universitätsstrasse 2, 8092 Zürich, Switzerland
| | - René M Rossi
- Laboratory for Biomimetic Membranes and Textiles, Empa, Swiss Federal Laboratories for Materials Science and Technology, Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland
- Department of Health Science and Technology, Swiss Federal Institute of Technology Zürich (ETHZ), Universitätsstrasse 2, 8092 Zürich, Switzerland
| | - Dominique Derome
- Department of Civil and Building Engineering, Université de Sherbrooke, J1K 2R1 Sherbrooke, Canada
| | - Jan Carmeliet
- Chair of Building Physics, Swiss Federal Institute of Technology Zürich (ETHZ), Stefano-Franscini-Platz 5, 8093 Zürich, Switzerland
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Fei L, Qin F, Zhao J, Derome D, Carmeliet J. Pore-Scale Study on Convective Drying of Porous Media. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6023-6035. [PMID: 35512019 DOI: 10.1021/acs.langmuir.2c00267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In this work, a numerical model for isothermal liquid-vapor phase change (evaporation) of the two-component air-water system is proposed based on the pseudopotential lattice Boltzmann method. Through the Chapman-Enskog multiscale analysis, we show that the model can correctly recover the macroscopic governing equations of the multicomponent multiphase system with a built-in binary diffusion mechanism. The model is verified based on the two-component Stefan problem where the measured binary diffusivity is consistent with theoretical analysis. The model is then applied to convective drying of a dual-porosity porous medium at the pore scale. The simulation captures a classical transition in the drying process of porous media, from the constant rate period (CRP, first phase) showing significant capillary pumping from large to small pores, to the falling rate period (FRP, second phase) with the liquid front receding in small pores. It is found that, in the CRP, the evaporation rate increases with the inflow Reynolds number (Re), while in the FRP, the evaporation curves almost collapse at different Res. The underlying mechanism is elucidated by introducing an effective Péclet number (Pe). It is shown that convection is dominant in the CRP and diffusion in the FRP, as evidenced by Pe > 1 and Pe < 1, respectively. We also find a log-law dependence of the average evaporation rate on the inflow Re in the CRP regime. The present work provides new insights into the drying physics of porous media and its direct modeling at the pore scale.
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Affiliation(s)
- Linlin Fei
- Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland
| | - Feifei Qin
- Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland
| | - Jianlin Zhao
- Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland
| | - Dominique Derome
- Department of Civil and Building Engineering, Université de Sherbrooke, Sherbrooke, Quebec J1K 2R1, Canada
| | - Jan Carmeliet
- Chair of Building Physics, Department of Mechanical and Process Engineering, ETH Zürich (Swiss Federal Institute of Technology in Zürich), Zürich 8092, Switzerland
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Zahid F, Cunningham JA. Effect of Grain-Size Distribution on Temporal Evolution of Interfacial Area during Two-phase Flow in Porous Media. Transp Porous Media 2022. [DOI: 10.1007/s11242-022-01767-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Cai Z, Song Y. Implementing Contact Angle Hysteresis in Moving Mesh-Based Two-Phase Flow Numerical Simulations. ACS OMEGA 2021; 6:35711-35717. [PMID: 34984301 PMCID: PMC8717560 DOI: 10.1021/acsomega.1c05613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
Contact angle hysteresis is a common phenomenon in nature, which also plays an important role in industrial applications. A numerical model based on the moving mesh two-phase flow method is presented for modeling contact angle hysteresis. The implementation includes a displacement-based penalty method and a state variable method. The pinning, moving, and repinning of the contact lines can be simulated. This method is robust considering both two-dimensional and three-dimensional geometries. To further demonstrate the performance of this method, a fluid-solid interaction model with a cylinder fluctuating on a water surface considering contact angle hysteresis is demonstrated.
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Affiliation(s)
- Zheren Cai
- Key
Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street 2, 100190 Beijing, P. R. China
- University
of Chinese Academy of Sciences, Yuquan Road No. 19A, 100049 Beijing, P. R. China
| | - Yanlin Song
- Key
Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street 2, 100190 Beijing, P. R. China
- University
of Chinese Academy of Sciences, Yuquan Road No. 19A, 100049 Beijing, P. R. China
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Talbi M, Prat M. Coupling between internal and external mass transfer during stage-1 evaporation in capillary porous media: Interfacial resistance approach. Phys Rev E 2021; 104:055102. [PMID: 34942821 DOI: 10.1103/physreve.104.055102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 10/12/2021] [Indexed: 11/07/2022]
Abstract
The coupling boundary condition to be imposed at the evaporative surface of a porous medium is studied from pore network simulations considering the capillary regime. This paper highlights the formation of a thin edge effect region of smaller saturation along the evaporative surface. It is shown that this thin region forms in the breakthrough period at the very beginning of the drying process. The size of this region is studied and shown to be not network size dependent. This region is shown to be the locus of a nonlocal equilibrium effect. The features lead to the consideration of a coupling boundary condition involving an interfacial mass transfer resistance and an external mass transfer resistance. Contrary to previous considerations, it is shown that both resistances depend on the variation of the saturation, i.e., the fluid topology, and the size of the external mass transfer layer, i.e., the mass transfer rate. This is explained by the evolution of the vapor partial pressure distribution at the surface which becomes increasingly heterogeneous during evaporation and depends on both the evolving fluid distribution in the interfacial region and the mass transfer rate. However, the geometric effects due to the configuration of the fluids can be separated from rate effects that arise due to the nonequilibrium mass transport.
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Affiliation(s)
- Marouane Talbi
- Institut de Mécanique des Fluides de Toulouse,Université de Toulouse, Centre National de la Recherche Scientifique, Toulouse, France
| | - Marc Prat
- Institut de Mécanique des Fluides de Toulouse,Université de Toulouse, Centre National de la Recherche Scientifique, Toulouse, France
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