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Wang X, Yuan Z, Chen F, Yao X, Yu F, Wang S. Forced Wetting of Shear-Thinning Fluids in Confined Capillaries. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 39320980 DOI: 10.1021/acs.langmuir.4c02728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/27/2024]
Abstract
Dynamic wetting in confined spaces is pivotal for the functional efficiency of biological organisms and offers significant potential for optimizing microdevices. The fluids encountered in such scenarios often exhibit shear-thinning behavior, which gives rise to complex interfacial phenomena. Here, we present an intriguing wetting phenomenon for shear-thinning fluids in confined capillary spaces. The employed shear-thinning fluids, carboxymethyl cellulose aqueous solutions with mass fractions of 0.5, 1.0, and 1.5 wt %, exhibit an intermediate state between ideal viscoelastic liquids, viscoelastic solids, and gel-like properties. We elucidate the geometric effect on its capillary wetting behavior, demonstrating that distortion of the moving contact line alters flow dynamics near the front corner, modifying the viscous resistance. This intricate interplay between the modified viscous resistance and the driving force results in a novel dynamic equilibrium distinct from that in Newtonian fluids. We further reveal that the viscous resistance in confined capillaries is controlled by both the morphology of the moving contact line and the shear-thinning exponent, particularly within the range of 0.7 to 1. This novel mechanism provides a pathway for manipulating the wetting dynamics of complex fluids in confined spaces.
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Affiliation(s)
- Xiong Wang
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Zhenyue Yuan
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Feipeng Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Kowloon, Hong Kong 999077, China
| | - Xiaoxue Yao
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Fanfei Yu
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
| | - Steven Wang
- Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong 999077, China
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Tokihiro JC, McManamen AM, Phana DN, Thongpang S, Blake TD, Theberge AB, Berthier J. On the dynamic contact angle of capillary-driven microflows in open channels. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.24.537941. [PMID: 37163094 PMCID: PMC10168213 DOI: 10.1101/2023.04.24.537941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The true value of the contact angle between a liquid and a solid is a thorny problem in capillary microfluidics. The Lucas-Washburn-Rideal (LWR) law assumes a constant contact angle during fluid penetration. However, recent experimental studies have shown lower liquid velocities than predicted by the LWR equation, which are attributed to a velocity-dependent dynamic contact angle that is larger than its static value. Inspection of fluid penetration in closed channels has confirmed that a dynamic angle is needed in the LWR equation. In this work, the dynamic contact angle in an open channel configuration is investigated using experimental data obtained with a range of liquids, aqueous and organic, and a PMMA substrate. We demonstrate that a dynamic contact angle must be used to explain the early stages of fluid penetration, i.e., at the start of the viscous regime, when flow velocities are sufficiently high. Moreover, the open channel configuration, with its free surface, enhances the effect of the dynamic contact angle, making its inclusion even more important. We found that for the liquids in our study, the molecular-kinetic theory (MKT) is the most accurate in predicting the effect of the dynamic contact angle on liquid penetration in open channels.
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Affiliation(s)
- Jodie C. Tokihiro
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
| | - Anika M. McManamen
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
| | - David N. Phana
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
| | - Sanitta Thongpang
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
| | | | - Ashleigh B. Theberge
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
- Department of Urology, University of Washington School of Medicine, Seattle, Washington 98105, United States
| | - Jean Berthier
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
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Si K, Liu C, Zhang D, Fang J, Yin H, Zhang C. Study of the Structural Changes and Internal Activator Transport Behavior after Activation of Aluminum-Based Flameless Ration Heaters: Experimental and Molecular Dynamics Simulations. ACS OMEGA 2023; 8:30929-30938. [PMID: 37663487 PMCID: PMC10468899 DOI: 10.1021/acsomega.3c02057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/25/2023] [Indexed: 09/05/2023]
Abstract
Aluminum-based flameless ration heaters (AFRHs) are heating elements in food packaging. Water is used to activate AFRHs. The material properties of each region of AFRHs were determined by X-ray diffraction, scanning electron microscopy, and hydrogen and heat generation. The results show that the internal cross-section shows stratification with hydrogen and heat production capacities of 105.2 ± 9.7 mL/g and 1435.0 ± 30.3 J/g for the outer layer, 27.1 ± 4.4 mL/g and 80.4 ± 3.1 J/g for the inner layer, and 1.1 ± 0.01 mL/g and 1.2 ± 0.05 J/g for the middle layer, respectively. According to the correspondence between aluminum and hydrogen in the aluminum-water reaction relationship, the reaction efficiency of the outer layer and the inner layer is as low as 64 and 80%, which is an indication of low reaction efficiency. To analyze the reasons for low reaction efficiency, a pore channel model of 3.5 nm tricalcium aluminate (C3A) was developed using molecular dynamics (MD) to reveal the adsorption behavior of the activator in the pore channel. The results show that the activator is subject to solid surface adsorption in the pore channel with a low diffusion coefficient. Oxygen atoms on the surface adsorb hydrogen atoms to form hydrogen bonds and sodium ions to form ionic bonds with calcium ions. This increases the retention time of the activator on the surface. The MD results explain the low reaction efficiency of AFRHs at the microscopic scale. Moreover, it provides ideas and a basis for the optimization of AFRHs.
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Affiliation(s)
- Kai Si
- Institute
of Food Science and Technology, Chinese
Academy of Agriculture Sciences, Key Laboratory of Agro-Products Quality
and Safety Control in Storage and Transport Process, Ministry of Agriculture
and Rural Affairs, Beijing 100193, China
| | - Chongxin Liu
- Institute
of Food Science and Technology, Chinese
Academy of Agriculture Sciences, Key Laboratory of Agro-Products Quality
and Safety Control in Storage and Transport Process, Ministry of Agriculture
and Rural Affairs, Beijing 100193, China
| | - Dequan Zhang
- Institute
of Food Science and Technology, Chinese
Academy of Agriculture Sciences, Key Laboratory of Agro-Products Quality
and Safety Control in Storage and Transport Process, Ministry of Agriculture
and Rural Affairs, Beijing 100193, China
| | - Jiajia Fang
- Institute
of Food Science and Technology, Chinese
Academy of Agriculture Sciences, Key Laboratory of Agro-Products Quality
and Safety Control in Storage and Transport Process, Ministry of Agriculture
and Rural Affairs, Beijing 100193, China
| | - Hang Yin
- College
of Water Conservancy and Civil Engineering, Shandong Agricultural University, Tai’an 271018, China
| | - Chunjiang Zhang
- Institute
of Food Science and Technology, Chinese
Academy of Agriculture Sciences, Key Laboratory of Agro-Products Quality
and Safety Control in Storage and Transport Process, Ministry of Agriculture
and Rural Affairs, Beijing 100193, China
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Advances in the Fabrication and Characterization of Superhydrophobic Surfaces Inspired by the Lotus Leaf. Biomimetics (Basel) 2022; 7:biomimetics7040196. [PMID: 36412724 PMCID: PMC9680393 DOI: 10.3390/biomimetics7040196] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 10/28/2022] [Accepted: 11/02/2022] [Indexed: 11/12/2022] Open
Abstract
Nature has proven to be a valuable resource in inspiring the development of novel technologies. The field of biomimetics emerged centuries ago as scientists sought to understand the fundamental science behind the extraordinary properties of organisms in nature and applied the new science to mimic a desired property using various materials. Through evolution, living organisms have developed specialized surface coatings and chemistries with extraordinary properties such as the superhydrophobicity, which has been exploited to maintain structural integrity and for survival in harsh environments. The Lotus leaf is one of many examples which has inspired the fabrication of superhydrophobic surfaces. In this review, the fundamental science, supported by rigorous derivations from a thermodynamic perspective, is presented to explain the origin of superhydrophobicity. Based on theory, the interplay between surface morphology and chemistry is shown to influence surface wetting properties of materials. Various fabrication techniques to create superhydrophobic surfaces are also presented along with the corresponding advantages and/or disadvantages. Recent advances in the characterization techniques used to quantify the superhydrophobicity of surfaces is presented with respect to accuracy and sensitivity of the measurements. Challenges associated with the fabrication and characterization of superhydrophobic surfaces are also discussed.
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Garcia Eijo PM, Cabaleiro JM, Artana G. Capillary Flow Dynamics in Composite Rectangular Microchannels with Rough Walls. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:13296-13304. [PMID: 36269940 DOI: 10.1021/acs.langmuir.2c02496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
In this article, we consider rectangular microchannels composed of glass and thin polymeric walls with different roughness in which opposed walls are of the same material but adjacent walls are not. We propose a model for fluid capillary transport into these rectangular microchannels when horizontally positioned and focus our research on how the microchannel aspect ratio modifies the motion during the initial viscous regimes. The model relies on an effective static contact angle and an effective friction coefficient that averages local magnitudes in the cross section. An extensive experimental investigation with different microchannels enabled us to obtain these coefficients for different aspect ratios. While for low aspect ratios, the effective contact angle presents the smallest values, the effective friction coefficient shows the larger ones. With rough surfaces, the spontaneous occurrence of pinning and depinning events associated with sharp wall defects notably reduces the effective static contact angle even when high aspect ratios are used. The obtained values of the effective friction coefficient show good agreement with previous literature investigations for rough and smooth lateral wall surfaces. Finally, we propose a nondimensional time to establish when contact angle effects dominate the dynamics. We found that for the materials and fluid properties used in this work, these effects become negligible for times larger than t ∼ 1 s.
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Affiliation(s)
- Pedro Manuel Garcia Eijo
- Laboratorio de Fluidodinámica, Facultad de Ingeniería, Universidad de Buenos Aires, C1063ACVBuenos Aires, Argentina
| | - Juan Martín Cabaleiro
- Laboratorio de Fluidodinámica, Facultad de Ingeniería, Universidad de Buenos Aires, C1063ACVBuenos Aires, Argentina
| | - Guillermo Artana
- Laboratorio de Fluidodinámica, Facultad de Ingeniería, Universidad de Buenos Aires, C1063ACVBuenos Aires, Argentina
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Extrand CW. Meniscus Formation in a Vertical Capillary Tube. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2346-2353. [PMID: 35138861 DOI: 10.1021/acs.langmuir.1c03226] [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 theoretical work, the energies associated with the formation of a meniscus in a small diameter capillary tube are analyzed. A mechanism for meniscus creation and an associated energy balance are proposed. Equations for work of wetting, surface energy, gravitational energy, and dissipation are derived. The relative magnitude of these quantities is compared, first to each other and then to energies from capillary rise. In capillary rise, the energy released as work of wetting is evenly split between gravitational energy stored in the liquid column and heat dissipated there. The analysis performed here suggests that meniscus formation is energetically distinct and more complex than capillary rise. In meniscus formation, most of the energy released as work of wetting is stored in the stretched air-liquid interface or dissipated in the bulk liquid; their relative distribution depends on the properties of the liquid and the tube.
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Ren T, Huang R, Gorte RJ, Lee D. Modulating Interactions between Molten Polystyrene and Porous Solids Using Atomic Layer Deposition. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:14520-14526. [PMID: 34865477 DOI: 10.1021/acs.langmuir.1c02604] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Understanding and modulating the interactions between molten polymers and porous solids is important for numerous processes and phenomena including catalytic conversion of polymers and fabrication of nanocomposites and nanostructured materials. Although changing the surface composition of pores would enable modulation of interactions between polymers and nanoporous solids, it is challenging to achieve such a control without inducing significant changes to the size and structure of nanopores. In this work, we demonstrate that the interactions between molten polystyrene (PS) and disordered packings of SiO2 nanoparticles (NPs) can be modulated by changing the surface composition of the NPs using atomic layer deposition (ALD). A disordered packing of silica NPs is modified with varying surface coverages of TiO2, WO3, and CaCO3, with coverages estimated by the mass gain and the refractive index change of NP packings. Based on the time required to fully infiltrate these ALD-modified NP packings via capillarity, the contact angles for PS on different surfaces prepared via ALD are determined. The contact angle gradually changes from that of pure SiO2 to that of the fully covered surfaces. The contact angles for PS on SiO2, TiO2, WO3, and CaCO3 are found to be 20, 62, 70, and 10°, respectively. Interestingly, the contact angles and interfacial energies between PS and the ALD-modified surfaces do not correlate strongly with the water contact angle of these surfaces; thus, caution must be exercised in predicting how a polymer would wet or interact with porous solids solely based on their hydrophilicity. The method presented in this work can be extended to study the interactions between a wide range of polymers and surfaces in porous media, which will have important implications for designing new catalytic materials for polymer upcycling reactions and novel NP-polymer composite films and membranes with enhanced mechanical and transport properties.
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Affiliation(s)
- Tian Ren
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Renjing Huang
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Raymond J Gorte
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Daeyeon Lee
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
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