1
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Zeng B, Kumar T, Wu H, Stark S, Hamza H, Zhao H, Xu H, Zhang X. Evolution of Morphology and Distribution of Salt Crystals on a Photothermal Layer during Solar Interfacial Evaporation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:14737-14747. [PMID: 37794656 DOI: 10.1021/acs.langmuir.3c02126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/06/2023]
Abstract
Solar interfacial evaporation (SIE) by leveraging photothermal conversion could be a clean and sustainable solution to the scarcity of fresh water, decontamination of wastewater, and steam sterilization. However, the process of salt crystallization on photothermal materials used in SIE, especially from saltwater evaporation, has not been completely understood. We report the temporal and spatial evolution of salt crystals on the photothermal layer during SIE. By using a typical oil lamp evaporator, we found that salt crystallization always initiates from the edge of the evaporation surface of the photothermal layer due to the local fast flux of the vapor to the surroundings. Interestingly, the salt crystals exhibit either compact or loose morphology, depending on the location and evaporation duration. By employing a suite of complementary analytical techniques of Raman and infrared spectroscopy and temperature mapping, we followed the evolution and spatial distribution of salt crystals, interfacial water, and surface temperature during evaporation. Our results suggested that the compact crystal structure may emerge from the recrystallization of salt in an initially porous structure, driven by continuous water evaporation from the porous and loose crystals. The holistic view provided in this study may lay the foundation for effective strategies for mitigation of the negative impact of salt crystallization in solar evaporation.
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Affiliation(s)
- Binglin Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
| | - Tanay Kumar
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
| | - Hongyan Wu
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
| | - Shane Stark
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
| | | | | | - Haolan Xu
- Future Industries Institute, University of South Australia, Adelaide, South Australia 5095, Australia
| | - Xuehua Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton T6G 1H9, Canada
- Physics of Fluids Group, Faculty of Science and Technology, University of Twente, Enschede 7500 AE, The Netherlands
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2
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Billet R, Zeng B, Lockhart J, Gattrell M, Zhao H, Zhang X. Dissolution dynamics of a binary switchable hydrophilicity solvent-polymer drop into an acidic aqueous phase. SOFT MATTER 2023; 19:295-305. [PMID: 36520098 DOI: 10.1039/d2sm01275h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Switchable hydrophilicity solvents (SHSs) are solvents defined by their ability to switch from their hydrophobic form to a hydrophilic form when brought into contact with an acidic trigger such as CO2. As a consequence, SHSs qualify as promising alternatives to volatile organic compounds during industrial solvent extraction processes, as greener and inexpensive methods can be applied to separate and recover SHSs. Furthermore, because of their less volatile nature, SHSs are less flammable and so increase the safety of a larger scale extraction process. In this work, we study the dynamics and in-drop phase separation during the dissolution process of a drop composed of a SHS and a polymer, triggered by an acid in the surrounding aqueous environment. From 70 different experimental conditions, we found a scaling relationship between the drop dissolution time and the initial volume with an overall scaling coefficient of ∼0.53. We quantitatively assessed and found a shorter dissolution time related to a decrease in the pH of the aqueous phase or an increase in the initial polymer concentration in the drop. Examining the internal state of the drop during the dissolution revealed an in-drop phase separation behavior, resulting in a porous morphology of the final polymer particle. Our experimental results provide a microscopic view of the SHS dissolution process from droplets, and findings may help design SHS extraction processes for particle formation from emulsions.
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Affiliation(s)
- Romain Billet
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, T6G 1H9, Canada.
| | - Binglin Zeng
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, T6G 1H9, Canada.
| | | | | | | | - Xuehua Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, T6G 1H9, Canada.
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3
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Baumli P, Hauer L, Lorusso E, Aghili AS, Hegner KI, D'Acunzi M, Gutmann JS, Dünweg B, Vollmer D. Linear shrinkage of hydrogel coatings exposed to flow: interplay between dissolution of water and advective transport. SOFT MATTER 2022; 18:365-371. [PMID: 34889343 DOI: 10.1039/d1sm01297e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We investigate the shrinkage of a surface-grafted water-swollen hydrogel under shear flows of oils by laser scanning confocal microscopy. Interestingly, external shear flows of oil lead to linear dehydration and shrinkage of the hydrogel for all investigated flow conditions irrespective of the chemical nature of the hydrogel. The reason is that the finite solubility of water in oil removes water from the hydrogel continuously by diffusion. The flow advects the water-rich oil, as demonstrated by numerical solutions of the underlying convection-diffusion equation. In line with this hypothesis, shear does not cause gel shrinkage for water-saturated oils or non-solvents. The solubility of water in the oil will tune the dehydration dynamics.
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Affiliation(s)
- Philipp Baumli
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Lukas Hauer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Emanuela Lorusso
- Deutsches Textilforschungszentrum Nord-West ÖP GmbH, Adlerstraße 1, 47798 Krefeld, Germany
| | | | - Katharina I Hegner
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Maria D'Acunzi
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Jochen S Gutmann
- Deutsches Textilforschungszentrum Nord-West ÖP GmbH, Adlerstraße 1, 47798 Krefeld, Germany
| | - Burkhard Dünweg
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
| | - Doris Vollmer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
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Basu S, Rao DCK, Chattopadhyay A, Chakraborty J. Dissolution dynamics of a vertically confined sessile droplet. Phys Rev E 2021; 103:013101. [PMID: 33601501 DOI: 10.1103/physreve.103.013101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Accepted: 12/16/2020] [Indexed: 11/07/2022]
Abstract
We experimentally investigate the dissolution of microscale sessile alcohol droplets in water under the influence of impermeable vertical confinement. The introduction of confinement suppresses the mass transport from the droplet to bulk medium in comparison with the nonconfined counterpart. Along with a buoyant plume, flow visualization reveals that the dissolution of a confined droplet is hindered by a mechanism called levitated toroidal vortex. The morphological changes in the flow due to the vortex-induced impediment alters the dissolution rate, resulting in enhancement of droplet lifetime. Further, we have proposed a modification in the key nondimensional parameters [Rayleigh number Ra^{'} (signifying buoyancy) and Sherwood number Sh^{'} (signifying mass flux)] and droplet lifetime τ_{c}^{'}, based on the hypothesis of linearly stratified droplet surroundings (with revised concentration difference ΔC^{'}), taking into account the geometry of the confinements. We show that experimental results on droplet dissolution under vertical confinement corroborate scaling relations Sh^{'}∼Ra^{'}^{1/4} and τ_{c}^{'}∼ΔC^{'}^{-5/4}. We also draw attention to the fact that the revised scaling law incorporating the geometry of confinements proposed in the present work can be extended to other known configurations such as droplet dissolution inside a range of channel dimensions, as encountered in a gamut of applications such as microfluidic technology and biomedical engineering.
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Affiliation(s)
- Saptarshi Basu
- Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India
| | - D Chaitanya Kumar Rao
- Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Ankur Chattopadhyay
- Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Joita Chakraborty
- Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India
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Li Z, Kiyama A, Zeng H, Lohse D, Zhang X. Speeding up biphasic reactions with surface nanodroplets. LAB ON A CHIP 2020; 20:2965-2974. [PMID: 32780079 DOI: 10.1039/d0lc00571a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Biphasic chemical reactions compartmentalized in small droplets offer advantages, such as streamlined procedures for chemical analysis, enhanced chemical reaction efficiency and high specificity of conversion. In this work, we experimentally and theoretically investigate the rate for biphasic chemical reactions between acidic nanodroplets on a substrate surface and basic reactants in a surrounding bulk flow. The reaction rate is measured by droplet shrinkage as the product is removed from the droplets by the flow. In our experiments, we determine the dependence of the reaction rate on the flow rate and the solution concentration. The theoretical analysis predicts that the life time τ of the droplets scales with Peclet number Pe and the reactant concentration in the bulk flow cre,bulk as τ∝ Pe-3/2cre,bulk-1, in good agreement with our experimental results. Furthermore, we found that the product from the reaction on an upstream surface can postpone the droplet reaction on a downstream surface, possibly due to the adsorption of interface-active products on the droplets in the downstream. The time of the delay decreases with increasing Pe of the flow and also with increasing reactant concentration in the flow, following the scaling same as that of the reaction rate with these two parameters. Our findings provide insight for the ultimate aim to enhance droplet reactions under flow conditions.
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Affiliation(s)
- Zhengxin Li
- Department of Chemical and Materials Engineering, Faculty of Engineering, University of Alberta, Edmonton, Alberta T6G 1H9, Canada.
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6
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Qian J, Arends GF, Zhang X. Surface Nanodroplets: Formation, Dissolution, and Applications. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:12583-12596. [PMID: 31132276 DOI: 10.1021/acs.langmuir.9b01051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Droplets at solid-liquid interfaces play essential roles in a broad range of fields, such as compartmentalized chemical reactions and conversions, high-throughput analysis and sensing, and super-resolution near-field imaging. Our recent work has focused on understanding and controlling the nanodroplet formation on solid surfaces in ternary liquid mixtures. These surface nanodroplets resemble tiny liquid lenses with a typical height of <1 μm and a volume of subfemtoliters. The solvent exchange is based on the process of displacing a droplet liquid solution by a poor solvent to create a transient oversaturation for droplet formation. A quantitative understanding of growth dynamics of surface nanodroplets in ternary liquid mixtures not only provides insight into the liquid-liquid phase separation induced by solvent addition in general but also has made it possible to control the droplet size well. This review article will summarize our findings in the last ∼5 years from the research with our collaborators. The first part will explain the fundamental aspects that are key to the formation and stability of surface nanodroplets. In the second part, we will highlight the applications of nanodroplets in chemical analysis and functional surface fabrication and finally point out future directions in droplet-based applications.
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Affiliation(s)
- Jiasheng Qian
- Department of Chemical and Materials Engineering , University of Alberta , Alberta T6G 1H9 , Canada
| | - Gilmar F Arends
- Department of Chemical and Materials Engineering , University of Alberta , Alberta T6G 1H9 , Canada
| | - Xuehua Zhang
- Department of Chemical and Materials Engineering , University of Alberta , Alberta T6G 1H9 , Canada
- Physics of Fluids Group, Max-Planck-Center Twente for Complex Fluid Dynamics, Mesa+ Institute and J. M. Burgers Centre for Fluid Dynamics, Department of Science and Technology , University of Twente , P.O. Box 217, 7500 AE Enschede , The Netherlands
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7
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Xie Q, Harting J. The effect of the liquid layer thickness on the dissolution of immersed surface droplets. SOFT MATTER 2019; 15:6461-6468. [PMID: 31292583 DOI: 10.1039/c9sm01048c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Droplets on a liquid-immersed solid surface are key elements in many applications, such as high-throughput chemical analysis and droplet-templated porous materials. Such surface droplets dissolve when the surrounding liquid is undersaturated and the dissolution process is usually treated analogous to a sessile droplet evaporating in air. Typically, theoretical models predict the mass loss rate of dissolving droplets as a function of droplet geometrical factors (radius, constant angle), and droplet material properties (diffusion constant and densities), where the thickness of the surrounding liquid layer is neglected. Here, we investigate, both numerically and theoretically, the effect of the liquid layer thickness on the dissolution of surface droplets. We perform 3D lattice Boltzmann simulations and obtain the density distribution and time evolution of droplet height during dissolution. Moreover, we find that the dissolution slows down and the lifetime linearly increases with increasing the liquid layer thickness. We propose a theoretical model based on a quasistatic diffusion equation which agrees quantitatively with simulation results for thick liquid layers. Our results offer insight to the fundamental understanding of dissolving surface droplets and can provide valuable guidelines for the design of devices where the droplet lifetime is of importance.
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Affiliation(s)
- Qingguang Xie
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands.
| | - Jens Harting
- Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600MB Eindhoven, The Netherlands. and Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Fürther Str. 248, 90429 Nürnberg, Germany
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Bao L, Pinchasik BE, Lei L, Xu Q, Hao H, Wang X, Zhang X. Control of Femtoliter Liquid on a Microlens: A Way to Flexible Dual-Microlens Arrays. ACS APPLIED MATERIALS & INTERFACES 2019; 11:27386-27393. [PMID: 31268287 DOI: 10.1021/acsami.9b06390] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Microlens arrays are key elements for light management in optoelectronic devices. The recent advancement in the wearable intelligent electronics has driven the development of flexible microlenses. In this work, we show a controllable and scalable surface-droplet-based strategy to create unconventional flexible polymer microlens arrays. The technique is underpinned by the morphological transition of femtoliter liquid on the surface of a microlens surrounded by a planar area. We found that the droplet liquid wetted the rim of the microlens first and gradually moved upward to the microlens surface with an increase in the liquid volume. The morphology evolution of the droplet is in good agreement with the predication from our simulations based on the interfacial energy minimization under the condition of the pinned boundary. The shape of the droplet on the microlens is well controlled by the droplet volume, aspect ratio of the microlens, and the interfacial energy of the droplets on the microlens. As a result, the obtained structures of one microlens partially covered by a droplet can be produced in arrays over a large scale, serving as templates for fabricating transparent polymer double microlens arrays for improved light emission from the optoelectronic device.
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Affiliation(s)
- Lei Bao
- School of Engineering , RMIT University , Melbourne , VIC 3001 , Australia
| | - Bat-El Pinchasik
- Department of Physics at Interfaces , Max Planck Institute for Polymer Research , Ackermannweg 10 , 55128 Mainz , Germany
- School of Mechanical Engineering, Faculty of Engineering , Tel-Aviv University , Ramat Aviv , 69978 Tel-Aviv , Israel
| | - Lei Lei
- School of Engineering , RMIT University , Melbourne , VIC 3001 , Australia
- School of Civil Engineering , Xuzhou University of Technology , Xuzhou , Jiangsu Province 221000 , China
| | - Qiwei Xu
- Department of Electrical and Computer Engineering , University of Alberta , Edmonton , Alberta T6G 2V4 , Canada
| | - Hao Hao
- Department of Chemistry and Biotechnology, School of Science , Swinburne University of Technology , Hawthorn , VIC 3122 , Australia
| | - Xihua Wang
- Department of Electrical and Computer Engineering , University of Alberta , Edmonton , Alberta T6G 2V4 , Canada
| | - Xuehua Zhang
- Department of Chemical & Materials Engineering, Faculty of Engineering , University of Alberta , Edmonton , Alberta T6G 1H9 , Canada
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9
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Peng S, Spandan V, Verzicco R, Lohse D, Zhang X. Growth dynamics of microbubbles on microcavity arrays by solvent exchange: Experiments and numerical simulations. J Colloid Interface Sci 2018; 532:103-111. [DOI: 10.1016/j.jcis.2018.07.111] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/24/2018] [Accepted: 07/25/2018] [Indexed: 11/30/2022]
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10
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Li X, Wang Y, Zeng B, Li Y, Tan H, Zandvliet HJW, Zhang X, Lohse D. Entrapment and Dissolution of Microbubbles Inside Microwells. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10659-10667. [PMID: 30102544 PMCID: PMC6136092 DOI: 10.1021/acs.langmuir.8b02173] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Revised: 08/10/2018] [Indexed: 05/20/2023]
Abstract
The formation and evolution of immersed surface micro- and nanobubbles are essential in various practical applications, such as the usage of superhydrophobic materials, drug delivery, and mineral flotation. In this work, we investigate the entrapment of microbubbles on a hydrophobic surface, structured with microwells, when water flow passes along, and the subsequent microbubble dissolution. At entrapment, the microbubble is initially pinned at the edge of the microwell. At some point, the three-phase contact line detaches from one side of the edge and separates from the wall, after which it further recedes. We systematically investigate the evolution of the footprint diameter and the contact angle of the entrapped microbubbles, which reveals that the dissolution process is in the constant contact angle mode. By varying the gas undersaturation level, we quantify how a high gas undersaturation enhances the dissolution process, and compare with simplified theoretical predictions for dissolving bubbles on a plane surface. We find that geometric partial blockage effects of the diffusive flux out of the microbubble trapped in the microwell lead to reduced dissolution rates.
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Affiliation(s)
- Xiaolai Li
- School
of Mechanical Engineering and Automation and Beijing Advanced Innovation Center
for Biomedical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing 100191, China
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
| | - Yuliang Wang
- School
of Mechanical Engineering and Automation and Beijing Advanced Innovation Center
for Biomedical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing 100191, China
- E-mail: (Y.W.)
| | - Binglin Zeng
- School
of Mechanical Engineering and Automation and Beijing Advanced Innovation Center
for Biomedical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing 100191, China
| | - Yanshen Li
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
| | - Huanshu Tan
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
| | - Harold J. W. Zandvliet
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
| | - Xuehua Zhang
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
- Department
of Chemical and Materials Engineering, University
of Alberta, 12-211 Donadeo
Innovation Centre for Engineering, Edmonton, Alberta, Canada T6G1H9
- E-mail: (X.Z.)
| | - Detlef Lohse
- Physics of Fluids Group, Department of Applied Physics, J. M. Burgers
Centre for Fluid Dynamics and Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The
Netherlands
- E-mail: (D.L.)
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