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Smith ER, Theodorakis PE. Multiscale simulation of fluids: coupling molecular and continuum. Phys Chem Chem Phys 2024; 26:724-744. [PMID: 38113114 DOI: 10.1039/d3cp03579d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
Computer simulation is an important tool for scientific progress, especially when lab experiments are either extremely costly and difficult or lack the required resolution. However, all of the simulation methods come with limitations. In molecular dynamics (MD) simulation, the length and time scales that can be captured are limited, while computational fluid dynamics (CFD) methods are built on a range of assumptions, from the continuum hypothesis itself, to a variety of closure assumptions. To address these issues, the coupling of different methodologies provides a way to retain the best of both methods. Here, we provide a perspective on multiscale simulation based on the coupling of MD and CFD with each a distinct part of the same simulation domain. This style of coupling allows molecular detail to be present only where it is needed, so CFD can model larger scales than possible with MD alone. We present a unified perspective of the literature, showing the links between the two main types of coupling, state and flux, and discuss the varying assumptions in their use. A unique challenge in such coupled simulation is obtaining averages and constraining local parts of a molecular simulation. We highlight that incorrect localisation has resulted in an error in the literature. We then finish with some applications, focused on the simulation of fluids. Thus, we hope to motivate further research in this exciting area with applications across the spectrum of scientific disciplines.
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Affiliation(s)
- Edward R Smith
- Department of Mechanical and Aerospace Engineering, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
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2
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Arbabi S, Deuar P, Denys M, Bennacer R, Che Z, Theodorakis PE. Molecular dynamics simulation of the coalescence of surfactant-laden droplets. SOFT MATTER 2023; 19:8070-8080. [PMID: 37801284 DOI: 10.1039/d3sm01046e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
We investigate the coalescence of surfactant-laden water droplets by using several different surfactant types and a wide range of concentrations by means of a coarse-grained model obtained by the statistical associating fluid theory. Our results demonstrate in detail a universal mass transport mechanism of surfactant across many concentrations and several surfactant types during the process. Coalescence initiation is seen to occur via a single pinch due to aggregation of surface surfactant, and its remnants tend to become engulfed in part inside the forming bridge. Across the board we confirm the existence of an initial thermal regime with constant bridge width followed by a later inertial regime with bridge width scaling roughly as the square root of time, but see no evidence of an intermediate viscous regime. Coalescence becomes slower as surfactant concentration grows, and we see evidence of the appearance of a further slowdown of a different nature for several times the critical concentration. We anticipate that our results provide further insights in the mechanisms of coalescence of surfactant-laden droplets.
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Affiliation(s)
- Soheil Arbabi
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
| | - Piotr Deuar
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
| | - Mateusz Denys
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
| | - Rachid Bennacer
- Université Paris-Saclay, CentraleSupélec, ENS Paris-Saclay, CNRS, LMPS - Laboratoire de Mécanique Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Zhizhao Che
- State Key Laboratory of Engines, Tianjin University, 300350 Tianjin, China
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3
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Fan Y, Wang Y. Deposition and Spread of Aqueous Pesticide Droplets on Hydrophobic/Superhydrophobic Surfaces by Fast Aggregation of Surfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5631-5640. [PMID: 37053578 DOI: 10.1021/acs.langmuir.3c00282] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Deposition and spread of aqueous droplets on hydrophobic/superhydrophobic surfaces are of great significance in many practical applications, such as spraying, coating, and printing, and particularly in improving pesticide utilization efficiency because the intrinsic hydrophobicity/superhydrophobicity of most plant leaves results in serious loss of water-based pesticides during spraying. It has been found that proper surfactants can promote the droplet spread on such surfaces. However, most reports involved the effects of surfactants on the spread of the gently released droplets over hydrophobic or highly hydrophobic substrates, while the situation on superhydrophobic substrates has rarely been explored. Moreover, high-speed impact makes it extremely difficult to deposit and spread the aqueous droplets on superhydrophobic surfaces; thus, the deposition and spread have just been achieved by surfactants in recent years. Here, we give an overview concerning the influence factors on the deposition and spreading performance of gently released and high-speed impacted droplets on hydrophobic/superhydrophobic substrates and emphasize the effects of fast aggregation of surfactants at the interface and in solution. We also outline perspectives on the future development of surfactant-assisted deposition and spreading after high-speed impact.
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Affiliation(s)
- Yaxun Fan
- CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Yilin Wang
- CAS Key Laboratory of Colloid, Interface and Chemical Thermodynamics, CAS Research/Education Center for Excellence in Molecular Sciences and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of Chinese Academy of Sciences, Beijing 100049, P. R. China
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4
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Vittal LVM, Rookes J, Boyd B, Cahill D. Analysis of plant cuticles and their interactions with agrochemical surfactants using a 3D printed diffusion chamber. PLANT METHODS 2023; 19:37. [PMID: 37005584 PMCID: PMC10067233 DOI: 10.1186/s13007-023-00999-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 02/20/2023] [Indexed: 06/19/2023]
Abstract
BACKGROUND Decades of research is available on their effects of single component surfactant on active ingredient diffusion across plant cuticular membranes, but ingredient diffusion is rarely analysed in the presence of commercial surfactants. Also, diffusion studies require expensive or specialized apparatus the fabrication of which often requires skilled labour and specialized facilities. In this research we have addressed both problems where the effects of four commercially available surfactants on a known tracer molecule were investigated using a 3D printed customized diffusion chamber. RESULTS As a proof-of-concept a customized 3D printed diffusion chamber was devised using two different thermoplastics and was successfully used in a range of diffusion tests . The effect of various solvents and surfactants on S. lycopersicum cuticular membrane indicated an increased rate of flux of tracer molecules across the membranes. This research has validated the application of 3D printing in diffusion sciences and demonstrated the flexibility and potential of this technique. CONCLUSIONS Using a 3D printed diffusion apparatus, the effect of commercial surfactants on molecular diffusion through isolated plant membranes was studied. Further, we have included here the steps involved in material selection, design, fabrication, and post processing procedures for successful recreation of the chamber. The customizability and rapid production process of the 3D printing demonstrates the power of additive manufacturing in the design and use of customizable labware.
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Affiliation(s)
- Lakshmi Venkatesha Manyu Vittal
- Faculty of Science Engineering and Built Environment, School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Geelong, VIC 3216 Australia
| | - James Rookes
- Faculty of Science Engineering and Built Environment, School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Geelong, VIC 3216 Australia
| | - Ben Boyd
- Department of Pharmacy, University of Copenhagen and Monash Institute of Pharmaceutical Sciences, Monash University, Parkville Campus, 381 Royal Parade, Parkville, VIC 3052 Australia
| | - David Cahill
- Faculty of Science Engineering and Built Environment, School of Life and Environmental Sciences, Deakin University, Geelong Waurn Ponds Campus, Geelong, VIC 3216 Australia
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5
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Nuthalapati K, Sheng YJ, Tsao HK. Abnormal wetting dynamics of Silwet-laden droplets on partially wetting substrates. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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6
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Nuthalapati K, Sheng YJ, Tsao HK. Anomalous interfacial dynamics of pendant droplets of N,N-dimethylformamide containing Silwet. J Taiwan Inst Chem Eng 2022. [DOI: 10.1016/j.jtice.2022.104282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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7
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Egorov SA. Bulk phase behavior and interfacial properties of binary mixtures of Lennard-Jones chains and solvent: a density functional theory study. SOFT MATTER 2022; 18:1034-1043. [PMID: 35019927 DOI: 10.1039/d1sm01722e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
A Density Functional Theory study is performed to analyze both bulk and interfacial properties of solvent-polymer binary mixtures. The effects of increasing polymer chain length on the bulk phase diagram morphology and interfacial tension are presented and compared to the prior simulation results. Good agreement between simulation and Density Functional Theory is found, including its ability to reproduce the density inversion phenomenon for highly asymmetric solvent-polymer binary mixtures. The data on the interfacial tensions is used to compute contact angles of the mixture at a planar wall, with particular focus on the wetting transition. The dependence of the wetting temperature on the polymer chain length and the mixture composition is analyzed in detail.
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Affiliation(s)
- Sergei A Egorov
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901, USA.
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8
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Theodorakis PE, Wang Y, Chen A, Liu B. Off-Lattice Monte-Carlo Approach for Studying Nucleation and Evaporation Phenomena at the Molecular Scale. MATERIALS (BASEL, SWITZERLAND) 2021; 14:2092. [PMID: 33919063 PMCID: PMC8122685 DOI: 10.3390/ma14092092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/19/2021] [Accepted: 04/19/2021] [Indexed: 11/16/2022]
Abstract
Droplet nucleation and evaporation are ubiquitous in nature and many technological applications, such as phase-change cooling and boiling heat transfer. So far, the description of these phenomena at the molecular scale has posed challenges for modelling with most of the models being implemented on a lattice. Here, we propose an off-lattice Monte-Carlo approach combined with a grid that can be used for the investigation of droplet formation and evaporation. We provide the details of the model, its implementation as Python code, and results illustrating its dependence on various parameters. The method can be easily extended for any force-field (e.g., coarse-grained, all-atom models, and external fields, such as gravity and electric field). Thus, we anticipate that the proposed model will offer opportunities for a wide range of studies in various research areas involving droplet formation and evaporation and will also form the basis for further method developments for the molecular modelling of such phenomena.
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Affiliation(s)
| | - Yongjie Wang
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland;
| | - Aiqiang Chen
- Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin 300134, China;
| | - Bin Liu
- Tianjin Key Laboratory of Refrigeration Technology, Tianjin University of Commerce, Tianjin 300134, China;
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9
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Hu SW, Chen KY, Sheng YJ, Tsao HK. Directed self-propulsion of droplets on surfaces absent of gradients for cargo transport. J Colloid Interface Sci 2021; 586:469-478. [PMID: 33183760 DOI: 10.1016/j.jcis.2020.10.110] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/25/2020] [Accepted: 10/26/2020] [Indexed: 11/30/2022]
Abstract
HYPOTHESIS Manipulating droplet transportation without inputting work is desired and important in microfluidic systems. Although the creation of wettability gradient on surfaces has been employed to achieve this goal, the transport distance is very limited, hindering its applications in long-term operations. EXPERIMENTS Here, we show that programming long-ranged transport of droplets on surfaces can be achieved by the addition of trisiloxane surfactants and the creation of deep grooves. The former provides Marangoni stress to actuate the droplet motion and also reduces the inherent contact line pinning. The latter acts as a railing to guide the motion of surfactant-laden droplets to follow various layouts with geometric features of roads. FINDINGS It is found that the droplets with microliters can move over 20 cm. This work-free method is applicable to a variety of substrate materials and liquids. By using self-running shuttles, a convenient platform for liquid cargos transport is developed and demonstrated. Moreover, the coalescence of cargos carried by different shuttles is accomplished in a three-branch layout, revealing new droplet microreactors.
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Affiliation(s)
- Ssu-Wei Hu
- Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan, ROC
| | - Kuan-Yu Chen
- Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan, ROC
| | - Yu-Jane Sheng
- Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan, ROC.
| | - Heng-Kwong Tsao
- Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan, ROC; Department of Physics, National Central University, Jhongli 320, Taiwan, ROC.
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10
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Venzmer J. Superspreading - Has the mystery been unraveled? Adv Colloid Interface Sci 2021; 288:102343. [PMID: 33359962 DOI: 10.1016/j.cis.2020.102343] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 12/08/2020] [Accepted: 12/09/2020] [Indexed: 10/22/2022]
Abstract
Superspreading is a fascinating phenomenon first observed about 30 years ago with dilute solutions of trisiloxane surfactants on hydrophobic substrates. Although many groups all over the world have contributed considerably to solve the scientific challenges involved, the reasons why only some trisiloxane surfactants promote superspreading, whereas others of similar chemical structure behave more like ordinary surfactants, has remained a mystery up to now. A number of original papers and reviews on superspreading have been published in recent years. The driving force still proposed today is most often Marangoni flow. This is, however, in contradiction with recent results showing that superspreading only starts after a surface tension gradient between apex and leading edge has been eliminated. From foam film experiments unrelated to wetting, there is evidence for "dangling" bilayers attached to the air/water interface only in case of the superspreading trisiloxane surfactants. By combining this and other published experimental findings, a new hypothesis of the mode of action is put forward: Advancing by "rolling action" at the leading edge, and the supply of surfactant by "unzippering" of the dangling bilayers all over the surface of the drop; this hypothesis even fulfills basic thermodynamic requirements.
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11
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12
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Superspreading performance of branched ionic trimethylsilyl surfactant Mg(AOTSiC)2. Colloids Surf A Physicochem Eng Asp 2020. [DOI: 10.1016/j.colsurfa.2020.125277] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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13
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Walker CC, Genzer J, Santiso EE. Effect of Poly(vinyl butyral) Comonomer Sequence on Adhesion to Amorphous Silica: A Coarse-Grained Molecular Dynamics Study. ACS APPLIED MATERIALS & INTERFACES 2020; 12:47879-47890. [PMID: 32921047 DOI: 10.1021/acsami.0c10747] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Modulating a comonomer sequence, in addition to the overall chemical composition, is the key to unlocking the true potential of many existing commercial copolymers. We employ coarse-grained molecular dynamics (MD) simulations to study the behavior of random-blocky poly(vinyl butyral-co-vinyl alcohol) (PVB) melts in contact with an amorphous silica surface, representing the interface found in laminated safety glass. Our two-pronged coarse-graining approach utilizes both macroscopic thermophysical data and all-atom MD simulation data. Polymer-polymer nonbonded interactions are described by the fused-sphere SAFT-γ Mie equation of state, while bonded interactions are derived using Boltzmann inversion to match the bond and angle distributions from all-atom PVB chains. Spatially dependent polymer-surface interactions are mapped from a hydroxylated all-atom amorphous silica slab model and all-atom monomers to an external potential acting on the coarse-grained sites. We discovered an unexpected complex relationship between the blockiness parameter and the adhesion energy. The adhesion strength between PVB copolymers with intermediate VA content and silica was found to be maximal for random-blocky copolymers with a moderately high degree of blockiness rather than for diblock copolymers. We attribute this to two main factors: (1) changes in morphology, which dramatically alter the number of VA beads interacting with the surface and (2) a non-negligible contribution of vinyl butyral (VB) monomers to adhesion energy because of their preference to adsorb to zones with low hydroxyl density on the silica surface.
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Affiliation(s)
- Christopher C Walker
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Jan Genzer
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Erik E Santiso
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
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14
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Surrogate Models for Studying the Wettability of Nanoscale Natural Rough Surfaces Using Molecular Dynamics. ENERGIES 2020. [DOI: 10.3390/en13112770] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A molecular modeling methodology is presented to analyze the wetting behavior of natural surfaces exhibiting roughness at the nanoscale. Using atomic force microscopy, the surface topology of a Ketton carbonate is measured with a nanometer resolution, and a mapped model is constructed with the aid of coarse-grained beads. A surrogate model is presented in which surfaces are represented by two-dimensional sinusoidal functions defined by both an amplitude and a wavelength. The wetting of the reconstructed surface by a fluid, obtained through equilibrium molecular dynamics simulations, is compared to that observed by the different realizations of the surrogate model. A least-squares fitting method is implemented to identify the apparent static contact angle, and the droplet curvature, relative to the effective plane of the solid surface. The apparent contact angle and curvature of the droplet are then used as wetting metrics. The nanoscale contact angle is seen to vary significantly with the surface roughness. In the particular case studied, a variation of over 65° is observed between the contact angle on a flat surface and on a highly spiked (Cassie–Baxter) limit. This work proposes a strategy for systematically studying the influence of nanoscale topography and, eventually, chemical heterogeneity on the wettability of surfaces.
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15
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Walker CC, Genzer J, Santiso EE. Extending the fused-sphere SAFT-γ Mie force field parameterization approach to poly(vinyl butyral) copolymers. J Chem Phys 2020; 152:044903. [DOI: 10.1063/1.5126213] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Affiliation(s)
- Christopher C. Walker
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Jan Genzer
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
| | - Erik E. Santiso
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA
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16
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Nam G, Yoon SH. Predicting the temporal wetting of porous, surfactant-added polydimethylsiloxane (PDMS). J Colloid Interface Sci 2019; 556:503-513. [PMID: 31473540 DOI: 10.1016/j.jcis.2019.08.081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/22/2019] [Accepted: 08/22/2019] [Indexed: 10/26/2022]
Abstract
Diverse surface/bulk treatments have been introduced to overcome the interfacial limitations of pristine (or untreated) PDMS, thus extending the possible applications of PDMS in micro/nano device development. Despite of extensive efforts, the temporal wetting change of PDMS induced by surface/bulk treatments still remains incompletely understood. We prepared 3 kinds of physicochemically treated PDMS blocks using widely used surface/bulk treatments-3D interconnected pore network formation, biocompatible surfactant (i.e., Silwet L-77) addition, and combination of both. Their wetting nature was characterized by measuring the time profile of water contact angle. A 3D interconnected pore network formation produced a time-invariant decrease in PDMS wettability; a surfactant addition increased the PDMS wettability in a time-variant way; a combination of pore network formation and surfactant addition had a combined effect. The measurement led to the successful development of a model for predicting the temporal wetting change in PDMS caused by variances in pore size and surfactant concentration. The accuracy of our model was verified by comparing experimental results with model predictions. This model will result in better understanding of polymer interface.
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Affiliation(s)
- Gyungmok Nam
- Department of Mechanical Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Sang-Hee Yoon
- Department of Mechanical Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea.
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17
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Theodorakis PE, Smith ER, Müller EA. Spreading of aqueous droplets with common and superspreading surfactants. A molecular dynamics study. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.123810] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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18
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Molecular Dynamics Simulation of the Superspreading of Surfactant-Laden Droplets. A Review. FLUIDS 2019. [DOI: 10.3390/fluids4040176] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Superspreading is the rapid and complete spreading of surfactant-laden droplets on hydrophobic substrates. This phenomenon has been studied for many decades by experiment, theory, and simulation, but it has been only recently that molecular-level simulation has provided significant insights into the underlying mechanisms of superspreading thanks to the development of accurate force-fields and the increase of computational capabilities. Here, we review the main advances in this area that have surfaced from Molecular Dynamics simulation of all-atom and coarse-grained models highlighting and contrasting the main results and discussing various elements of the proposed mechanisms for superspreading. We anticipate that this review will stimulate further research on the interpretation of experimental results and the design of surfactants for applications requiring efficient spreading, such as coating technology.
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19
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Pervaje AK, Walker CC, Santiso EE. Molecular simulation of polymers with a SAFT-γ Mie approach. MOLECULAR SIMULATION 2019. [DOI: 10.1080/08927022.2019.1645331] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Amulya K. Pervaje
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher C. Walker
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Erik E. Santiso
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
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20
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Superspreading on Hydrophobic Substrates: Effect of Glycerol Additive. COLLOIDS AND INTERFACES 2019. [DOI: 10.3390/colloids3020051] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The spreading of solutions of three trisiloxane surfactants on two hydrophobic substrates, polyethylene and polyvinylidenefluoride, was studied with the addition of 0–40 mass % of glycerol. It was found that all the surfactant solutions spread faster than silicone oil of the same viscosity, confirming the existence of a mechanism which accelerates the spreading of the surfactant solutions. For the non-superspreading surfactant, BT-233, addition of glycerol improved the spreading performance on polyvinylidenefluoride and resulted in a transition from partial to complete wetting on polyethylene. The fastest spreading was observed for BT-233 at a concentration of 2.5 g/L, independent of glycerol content. For the superspreading surfactants, BT-240 and BT-278, the concentration at which the fastest spreading occurs systematically increased with concentration of glycerol on both substrates from 1.25 g/L for solutions in water to 10 g/L for solutions in 40% glycerol/water mixture. Thus, the surfactant equilibration rate (and therefore formation of surface tension gradients) and Marangoni flow are important components of a superspreading mechanism. De-wetting of the solutions containing glycerol, once spread on the substrates, resulted in the formation of circular drop patterns. This is in contrast to the solely aqueous solutions where the spread film shrank due to evaporation, without any visible traces being left behind.
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21
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Shahruddin S, Jiménez-Serratos G, Britovsek GJP, Matar OK, Müller EA. Fluid-solid phase transition of n-alkane mixtures: Coarse-grained molecular dynamics simulations and diffusion-ordered spectroscopy nuclear magnetic resonance. Sci Rep 2019; 9:1002. [PMID: 30700804 PMCID: PMC6353884 DOI: 10.1038/s41598-018-37799-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Accepted: 12/12/2018] [Indexed: 11/10/2022] Open
Abstract
Wax appearance temperature (WAT), defined as the temperature at which the first solid paraffin crystal appears in a crude oil, is one of the key flow assurance indicators in the oil industry. Although there are several commonly-used experimental techniques to determine WAT, none provides unambiguous molecular-level information to characterize the phase transition between the homogeneous fluid and the underlying solid phase. Molecular Dynamics (MD) simulations employing the statistical associating fluid theory (SAFT) force field are used to interrogate the incipient solidification states of models for long-chain alkanes cooled from a melt to an arrested state. We monitor the phase change of pure long chain n-alkanes: tetracosane (C24H50) and triacontane (C30H62), and an 8-component surrogate n-alkane mixture (C12-C33) built upon the compositional information of a waxy crude. Comparison to Diffusion Ordered Spectroscopy Nuclear Magnetic Resonance (DOSY NMR) results allows the assessment of the limitations of the coarse-grained models proposed. We show that upon approach to freezing, the heavier components restrict their motion first while the lighter ones retain their mobility and help fluidize the mixture. We further demonstrate that upon sub-cooling of long n-alkane fluids and mixtures, a discontinuity arises in the slope of the self-diffusion coefficient with decreasing temperature, which can be employed as a marker for the appearance of an arrested state commensurate with conventional WAT measurements.
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Affiliation(s)
- S Shahruddin
- PETRONAS Research Sdn. Bhd, Lot 3288 & 3289 Off Jalan Ayer Itam, Kawasan Institusi Bangi, 43000, Kajang, Malaysia.,Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - G Jiménez-Serratos
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - G J P Britovsek
- Department of Chemistry, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - O K Matar
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - E A Müller
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
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22
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Sankaran A, Karakashev SI, Sett S, Grozev N, Yarin AL. On the nature of the superspreaders. Adv Colloid Interface Sci 2019; 263:1-18. [PMID: 30471569 DOI: 10.1016/j.cis.2018.10.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Revised: 10/17/2018] [Accepted: 10/22/2018] [Indexed: 10/27/2022]
Abstract
This is a review article on the basic and the latest achievements on superspreading. The complete and fast spreading of droplets on many surfaces in the nature is a special phenomenon discovered in 1960-ies Intensive studies on this phenomenon have been conducted since that time, but the mechanism of superspreading remained in completely unveiled till nowadays. Here we scrutinized the basic literature on superspreading from the last 25 years and also present results related to superspreaders acquired in the present work. The literature in superspreading can be divided to the following groups: (i) works on the properties of the trisiloxane surfactants; (ii) works on the mechanisms of superspreading; (iii) MD simulations; (iv) works on the effect of the trisiloxane surfactants on thin liquid films. There is a number of review articles published in the last decade related to mainly works from groups (i) and (ii). The works on MD simulations (iii) and the effects on trisiloxane surfactants on thin liquid films (iv) are still few despite they are important from the scientific view point. We conducted our own study on the effect of the superspreaders on foam films in rectangular frame and confirmed that the superspreaders cause powerful Marangoni effect within the foam films. Such a strong Marangoni effect has been never observed with the ordinary surfactants. We scrutinized and discussed the basic works from the groups (i)-(iv) on the superspreading and added our own investigation on the distinguishable effects of superspreaders and non-superspreaders on thin foam films. The work could be useful to both beginners and specialists in the field of wetting/de-wetting and superspreading.
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Smith ER, Theodorakis PE, Craster RV, Matar OK. Moving Contact Lines: Linking Molecular Dynamics and Continuum-Scale Modeling. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:12501-12518. [PMID: 29727189 DOI: 10.1021/acs.langmuir.8b00466] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Despite decades of research, the modeling of moving contact lines has remained a formidable challenge in fluid dynamics whose resolution will impact numerous industrial, biological, and daily life applications. On the one hand, molecular dynamics (MD) simulation has the ability to provide unique insight into the microscopic details that determine the dynamic behavior of the contact line, which is not possible with either continuum-scale simulations or experiments. On the other hand, continuum-based models provide a link to the macroscopic description of the system. In this Feature Article, we explore the complex range of physical factors, including the presence of surfactants, which governs the contact line motion through MD simulations. We also discuss links between continuum- and molecular-scale modeling and highlight the opportunities for future developments in this area.
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Rahman S, Lobanova O, Jiménez-Serratos G, Braga C, Raptis V, Müller EA, Jackson G, Avendaño C, Galindo A. SAFT-γ Force Field for the Simulation of Molecular Fluids. 5. Hetero-Group Coarse-Grained Models of Linear Alkanes and the Importance of Intramolecular Interactions. J Phys Chem B 2018; 122:9161-9177. [DOI: 10.1021/acs.jpcb.8b04095] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Sadia Rahman
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Olga Lobanova
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Guadalupe Jiménez-Serratos
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Carlos Braga
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Vasilios Raptis
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Erich A. Müller
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - George Jackson
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Carlos Avendaño
- School of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Amparo Galindo
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom
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25
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Chen CP, Lu F, Tong QX. Three tetrasiloxane-tailed cationic gemini surfactants: The effect of different spacer rigidity on surface properties and aggregation behaviors. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.06.112] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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26
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Badra AT, Zahaf H, Alla H, Roques-Carmes T. A numerical model of superspreading surfactants on hydrophobic surface. PHYSICS OF FLUIDS 2018; 30. [DOI: 10.1063/1.5041804] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Many contributions significantly on experimental and mathematical studies are made to understand the mechanism of superspreading. Only few numerical methods have been proposed which solve the system of equations with soluble and insoluble surfactants. Among them, we propose a computational fluid dynamics model, based on the volume of fluid technique, with the piecewise linear interface calculation method. Interface reconstruction is applied to simulate the time evolution of the dynamics of drop spreading of surfactants on a thin water layer. We have allowed the occurrence of both the regimes relating to a series of trisiloxane (M(D′EnOH)M), sodium dodecyl sulphate, and Tergitol NP10 surfactants drop on a thin water layer with the influence of Marangoni stress. The numerical data seem consistent with those experimental for both regimes. It validates predictions for the spreading exponent in which the law of the radius of the circular area covered by the surfactant grows as tα, where 0 < α < 1. The comparison of the numerical and experimental predictions by Lee et al. [“Spreading of trisiloxanes over thin aqueous layers,” Colloid J. 71, 365–369 (2009)] is well represented in both regimes. The numerical study confirms that the spreading rates during the first stage increase as the solubility increases. This finding suggests that the model is adequate for describing the spreading of surfactants on thin fluid layers.
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Affiliation(s)
- Ali Talha Badra
- Laboratoire de Physique des Matériaux et des Fluides, Université des Sciences et de la Technologie d’Oran 1 , BP 1505 El M’Naouar Bir el Djir, 31000 Oran, Algeria
| | - Hanane Zahaf
- Laboratoire de Physique des Matériaux et des Fluides, Université des Sciences et de la Technologie d’Oran 1 , BP 1505 El M’Naouar Bir el Djir, 31000 Oran, Algeria
| | - Hocine Alla
- Laboratoire de Physique des Matériaux et des Fluides, Université des Sciences et de la Technologie d’Oran 1 , BP 1505 El M’Naouar Bir el Djir, 31000 Oran, Algeria
| | - Thibault Roques-Carmes
- Université de Lorraine, Laboratoire Réactions et Génie des Procédés, UMR 7274 CNRS 2 , Nancy F-54000, France
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27
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Hadjittofis E, Isbell MA, Karde V, Varghese S, Ghoroi C, Heng JYY. Influences of Crystal Anisotropy in Pharmaceutical Process Development. Pharm Res 2018; 35:100. [PMID: 29556822 PMCID: PMC5859710 DOI: 10.1007/s11095-018-2374-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/19/2018] [Indexed: 01/27/2023]
Abstract
Crystalline materials are of crucial importance to the pharmaceutical industry, as a large number of APIs are formulated in crystalline form, occasionally in the presence of crystalline excipients. Owing to their multifaceted character, crystals were found to have strongly anisotropic properties. In fact, anisotropic properties were found to be quite important for a number of processes including milling, granulation and tableting. An understanding of crystal anisotropy and an ability to control and predict crystal anisotropy are mostly subjects of interest for researchers. A number of studies dealing with the aforementioned phenomena are grounded on over-simplistic assumptions, neglecting key attributes of crystalline materials, most importantly the anisotropic nature of a number of their properties. Moreover, concepts such as the influence of interfacial phenomena in the behaviour of crystalline materials during their growth and in vivo, are still poorly understood. The review aims to address concepts from a molecular perspective, focusing on crystal growth and dissolution. It begins with a brief outline of fundamental concepts of intermolecular and interfacial phenomena. The second part discusses their relevance to the field of pharmaceutical crystal growth and dissolution. Particular emphasis is given to works dealing with mechanistic understandings of the influence of solvents and additives on crystal habit. Furthermore, comments and perspectives, highlighting future directions for the implementation of fundamental concepts of interfacial phenomena in the rational understanding of crystal growth and dissolution processes, have been provided.
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Affiliation(s)
- Eftychios Hadjittofis
- Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Mark Antonin Isbell
- Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Vikram Karde
- Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Sophia Varghese
- DryProTech Laboratory, Chemical Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, Gujarat, 382355, India
| | - Chinmay Ghoroi
- DryProTech Laboratory, Chemical Engineering, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar, Gujarat, 382355, India
| | - Jerry Y Y Heng
- Surfaces and Particle Engineering Laboratory (SPEL), Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
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28
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Coarse-grained theoretical modeling and molecular simulations of nitrogen + n -alkanes: ( n -pentane, n -hexane, n -heptane, n -octane). J Supercrit Fluids 2017. [DOI: 10.1016/j.supflu.2017.01.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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29
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Theodorakis PE, Müller EA, Craster RV, Matar OK. Physical insights into the blood-brain barrier translocation mechanisms. Phys Biol 2017; 14:041001. [PMID: 28586313 DOI: 10.1088/1478-3975/aa708a] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The number of individuals suffering from diseases of the central nervous system (CNS) is growing with an aging population. While candidate drugs for many of these diseases are available, most of these pharmaceutical agents cannot reach the brain rendering most of the drug therapies that target the CNS inefficient. The reason is the blood-brain barrier (BBB), a complex and dynamic interface that controls the influx and efflux of substances through a number of different translocation mechanisms. Here, we present these mechanisms providing, also, the necessary background related to the morphology and various characteristics of the BBB. Moreover, we discuss various numerical and simulation approaches used to study the BBB, and possible future directions based on multi-scale methods. We anticipate that this review will motivate multi-disciplinary research on the BBB aiming at the design of effective drug therapies.
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30
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Jiménez-Serratos G, Herdes C, Haslam AJ, Jackson G, Müller EA. Group Contribution Coarse-Grained Molecular Simulations of Polystyrene Melts and Polystyrene Solutions in Alkanes Using the SAFT-γ Force Field. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02072] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Carmelo Herdes
- Department
of Chemical Engineering, University of Bath, Bath BA2 7AY, U.K
| | - Andrew J. Haslam
- Department
of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K
| | - George Jackson
- Department
of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K
| | - Erich A. Müller
- Department
of Chemical Engineering, Imperial College London, London SW7 2AZ, U.K
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31
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Arjmandi-Tash O, Kovalchuk NM, Trybala A, Kuchin IV, Starov V. Kinetics of Wetting and Spreading of Droplets over Various Substrates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4367-4385. [PMID: 28190350 DOI: 10.1021/acs.langmuir.6b04094] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
There has been a substantial increase in the number of publications in the field of wetting and spreading since 2010. This increase in the rate of publications can be attributed to the broader application of wetting phenomena in new areas. It is impossible to review such a huge number of publications; that is, some topics in the field of wetting and spreading are selected to be discussed below. These topics are as follows: (i) Contact angle hysteresis on smooth homogeneous solid surfaces via disjoining/conjoining pressure. It is shown that the hysteresis contact angles can be calculated via disjoining/conjoining pressure. The theory indicates that the equilibrium contact angle is closer to a static receding contact angle than to a static advancing contact angle. (ii) The wetting of deformable substrates, which is caused by surface forces action in the vicinity of the apparent three-phase contact line, leading to a deformation on the substrate. (iii) The kinetics of wetting and spreading of non-Newtonian liquid (blood) over porous substrates. We showed that in spite of the enormous complexity of blood, the spreading over porous substrate can be described using a relatively simple model: a power low-shear-thinning non-Newtonian liquid. (iv) The kinetics of spreading of surfactant solutions. In this part, new results related to various surfactant solution mixtures (synergy and crystallization) are discussed, which shows some possible direction for the future revealing of superspreading phenomena. (v) The kinetics of spreading of surfactant solutions over hair. Fundamental problems to be solved are identified.
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Affiliation(s)
- Omid Arjmandi-Tash
- Deparment of Chemical Engineering, Loughborough University , Loughborough LE11 3TU, U.K
| | - Nina M Kovalchuk
- Deparment of Chemical Engineering, Loughborough University , Loughborough LE11 3TU, U.K
- Institute of Biocolloid Chemistry , Kiev 03142, Ukraine
| | - Anna Trybala
- Deparment of Chemical Engineering, Loughborough University , Loughborough LE11 3TU, U.K
| | - Igor V Kuchin
- Deparment of Chemical Engineering, Loughborough University , Loughborough LE11 3TU, U.K
- Institute of Physical Chemistry and Electrochemistry RAS , Moscow 119071, Russia
| | - Victor Starov
- Deparment of Chemical Engineering, Loughborough University , Loughborough LE11 3TU, U.K
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32
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Lin J, Zhu M, Wu X, Zheng C, Liu Z, Wang Q, Lu D, He Q, Chen X. Microwave-assisted synthesis of trisiloxane superspreader and its superspreading behavior on plant leaves surfaces. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2016.09.079] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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33
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Morgado P, Lobanova O, Müller EA, Jackson G, Almeida M, Filipe EJM. SAFT-γ force field for the simulation of molecular fluids: 8. Hetero-segmented coarse-grained models of perfluoroalkylalkanes assessed with new vapour–liquid interfacial tension data. Mol Phys 2016. [DOI: 10.1080/00268976.2016.1218077] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Pedro Morgado
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
| | - Olga Lobanova
- Department of Chemical Engineering, Centre for Process Systems Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Erich A. Müller
- Department of Chemical Engineering, Centre for Process Systems Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - George Jackson
- Department of Chemical Engineering, Centre for Process Systems Engineering, Imperial College London, London SW7 2AZ, United Kingdom
| | - Miguel Almeida
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
| | - Eduardo J. M. Filipe
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
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34
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Kovalchuk NM, Trybala A, Arjmandi-Tash O, Starov V. Surfactant-enhanced spreading: Experimental achievements and possible mechanisms. Adv Colloid Interface Sci 2016; 233:155-160. [PMID: 26282600 DOI: 10.1016/j.cis.2015.08.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 08/04/2015] [Accepted: 08/04/2015] [Indexed: 11/18/2022]
Abstract
Surfactants are broadly used to improve wetting properties of aqueous formulations. The improvement is achieved by essential reduction of liquid/air and solid/liquid interfacial tensions resulting in the decrease of contact angle. For moderately hydrophobic substrates, there is a range of surfactants providing complete wetting of substrate. With the decrease of substrate surface energy, this range of surfactants reduces very quickly and only trisiloxane surfactant solutions are capable to wet completely such highly hydrophobic substrates as polypropylene and parafilm. That is why these surfactants are referred to as superspreaders. The most intriguing feature of wetting surfactant solutions is their ability to spread much faster than pure liquids with spread area, S, being proportional to time, t, S~t, as compared to S~t(0.2) for pure liquids, which wet completely the solid substrate. Trisiloxane surfactant solutions spread faster than other aqueous surfactant solutions, which also provide complete wetting, being superspreaders in the sense of spreading rate as well. The mechanism of fast spreading of surfactant solutions on hydrophobic substrates and much higher spreading rates for trisiloxane solutions are to be explained. Below the available experimental data on superspreading and surfactant-enhanced spreading are analysed/summarised, and possible mechanisms governing the fast spreading are discussed.
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Affiliation(s)
- N M Kovalchuk
- Department of Chemical Engineering, Loughborough University, Loughborough, UK; Institute of Biocolloid Chemistry, Kiev, Ukraine
| | - A Trybala
- Department of Chemical Engineering, Loughborough University, Loughborough, UK
| | - O Arjmandi-Tash
- Department of Chemical Engineering, Loughborough University, Loughborough, UK
| | - V Starov
- Department of Chemical Engineering, Loughborough University, Loughborough, UK.
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35
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Kovalchuk NM, Matar OK, Craster RV, Miller R, Starov VM. The effect of adsorption kinetics on the rate of surfactant-enhanced spreading. SOFT MATTER 2016; 12:1009-1013. [PMID: 26610693 DOI: 10.1039/c5sm02493e] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A comparison of the kinetics of spreading of aqueous solutions of two different surfactants on an identical substrate and their short time adsorption kinetics at the water/air interface has shown that the surfactant which adsorbs slower provides a higher spreading rate. This observation indicates that Marangoni flow should be an important part of the spreading mechanism enabling surfactant solutions to spread much faster than pure liquids with comparable viscosities and surface tensions.
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Affiliation(s)
- N M Kovalchuk
- Imperial College London, South Kensington Campus, London SW7 2AZ, UK and Institute of Biocolloid Chemistry, Kiev 03142, Ukraine
| | - O K Matar
- Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - R V Craster
- Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - R Miller
- Max Planck Institute of Colloids and Interfaces, Golm, D-14424, Germany
| | - V M Starov
- Loughborough University, Loughborough, LE 11 3TU, UK.
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36
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Theodorakis PE, Müller EA, Craster RV, Matar OK. Modelling the superspreading of surfactant-laden droplets with computer simulation. SOFT MATTER 2015; 11:9254-9261. [PMID: 26537741 DOI: 10.1039/c5sm02090e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The surfactant-driven superspreading of droplets on hydrophobic substrates is considered. A key element of the superspreading mechanism is the adsorption of surfactant molecules from the liquid-vapour interface onto the substrate through the contact line, which must be coordinated with the replenishment of interfaces with surfactant from the interior of the droplet. We use molecular dynamics simulations with coarse-grained force fields to provide a detailed structural description of the droplet shape and surfactant dynamics during the superspreading process. We also provide a simple method for accurate estimation of the contact angle subtended by the droplets at the contact line.
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Affiliation(s)
- Panagiotis E Theodorakis
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
| | - Erich A Müller
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
| | - Richard V Craster
- Department of Mathematics, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
| | - Omar K Matar
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
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37
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Jover J, Galindo A, Jackson G, Müller EA, Haslam AJ. Fluid–fluid coexistence in an athermal colloid–polymer mixture: thermodynamic perturbation theory and continuum molecular-dynamics simulation. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1047425] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Julio Jover
- Department of Chemical Engineering, Imperial College London , South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Amparo Galindo
- Department of Chemical Engineering, Imperial College London , South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - George Jackson
- Department of Chemical Engineering, Imperial College London , South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Erich A. Müller
- Department of Chemical Engineering, Imperial College London , South Kensington Campus, London, SW7 2AZ, United Kingdom
| | - Andrew J. Haslam
- Department of Chemical Engineering, Imperial College London , South Kensington Campus, London, SW7 2AZ, United Kingdom
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38
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Isele-Holder RE, Berkels B, Ismail AE. Smoothing of contact lines in spreading droplets by trisiloxane surfactants and its relevance for superspreading. SOFT MATTER 2015; 11:4527-4539. [PMID: 25955355 DOI: 10.1039/c4sm02298j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Superspreading, the greatly enhanced spreading of aqueous solutions of trisiloxane surfactants on hydrophobic substrates, is of great interest in fundamental physics and technical applications. Despite numerous studies in the last 20 years, the superspreading mechanism is still not well understood, largely because the molecular scale cannot be resolved appropriately either experimentally or using continuum simulations. The absence of molecular-scale knowledge has led to a series of conflicting hypotheses based on different assumptions of surfactant behavior. We report a series of large-scale molecular dynamics simulations of aqueous solutions of superspreading and non-superspreading surfactants on different substrates. We find that the transition from the liquid-vapor to the solid-liquid interface is smooth for superspreading conditions, allowing direct adsorption through the contact line. This finding complements a study [Karapetsas et al., J. Fluid Mech., 2011, 670, 5-37], which predicts that superspreading can occur if this adsorption path is possible. Based on the observed mechanism, we provide plausible explanations for the influence of the substrate hydrophobicity, the surfactant chain length, and the surfactant concentration on the superspreading phenomenon. We also briefly address that the observed droplet shape is a mechanism to overcome the Huh-Scriven paradox of infinite viscous dissipation at the contact line.
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Affiliation(s)
- Rolf E Isele-Holder
- Aachener Verfahrenstechnik, Molecular Simulations and Transformations, RWTH Aachen University, Schinkelstraße 2, 52062 Aachen, Germany.
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