1
|
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.
Collapse
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
| | | |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Dynamic wetting of various liquids: Theoretical models, experiments, simulations and applications. Adv Colloid Interface Sci 2023; 313:102861. [PMID: 36842344 DOI: 10.1016/j.cis.2023.102861] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 02/12/2023] [Accepted: 02/13/2023] [Indexed: 02/23/2023]
Abstract
Dynamic wetting is a ubiquitous phenomenon and frequently observed in our daily life, as exemplified by the famous lotus effect. It is also an interfacial process of upmost importance involving many cutting-edge applications and has hence received significantly increasing academic and industrial attention for several decades. However, we are still far away to completely understand and predict wetting dynamics for a given system due to the complexity of this dynamic process. The physics of moving contact lines is mainly ascribed to the full coupling with the solid surface on which the liquids contact, the atmosphere surrounding the liquids, and the physico-chemical characteristics of the liquids involved (small-molecule liquids, metal liquids, polymer liquids, and simulated liquids). Therefore, to deepen the understanding and efficiently harness wetting dynamics, we propose to review the major advances in the available literature. After an introduction providing a concise and general background on dynamic wetting, the main theories are presented and critically compared. Next, the dynamic wetting of various liquids ranging from small-molecule liquids to simulated liquids are systematically summarized, in which the new physical concepts (such as surface segregation, contact line fluctuations, etc.) are particularly highlighted. Subsequently, the related emerging applications are briefly presented in this review. Finally, some tentative suggestions and challenges are proposed with the aim to guide future developments.
Collapse
|
4
|
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.
Collapse
|
5
|
|
6
|
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]
|
7
|
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]
|
8
|
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.
Collapse
|
9
|
Iasella SV, Sun N, Zhang X, Corcoran TE, Garoff S, Przybycien TM, Tilton RD. Flow regime transitions and effects on solute transport in surfactant-driven Marangoni flows. J Colloid Interface Sci 2019; 553:136-147. [PMID: 31202050 DOI: 10.1016/j.jcis.2019.06.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/04/2019] [Accepted: 06/05/2019] [Indexed: 11/29/2022]
Abstract
HYPOTHESIS Surfactant-driven Marangoni flow on liquid films is predicted to depend on subphase depth and initial surface tension difference between the subphase and deposited surfactant solution drop. Changes in flow behavior will impact transport of soluble species entrained in the Marangoni flow along the surface. In extreme cases, the subphase film may rupture, limiting transport. Understanding this behavior is important for applications in drug delivery, coatings, and oil spill remediation. EXPERIMENTS A trans-illumination optical technique measured the subphase height profiles and drop content transport after drop deposition when varying initial subphase depth, surfactant concentration, and subphase viscosity. FINDINGS Three distinct flow regimes were identified depending on the subphase depth and surfactant concentration and mapped onto an operating diagram. These are characterized as a "central depression" bounded by an outwardly traveling ridge, an "annular depression" bounded by a central dome and the traveling ridge, and an "annular dewetting" when the subphase ruptures. Well above the critical micelle concentration, transitions between regimes occur at characteristic ratios of gravitational and initial surface tension gradient stresses; transitions shift when surfactant dilution during spreading weakens the stress before the completion of the spreading event. Drop contents travel with the ridge, but dewetting hinders transport.
Collapse
Affiliation(s)
- Steven V Iasella
- Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2).
| | - Ningguan Sun
- Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2)
| | - Xin Zhang
- Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2)
| | - Timothy E Corcoran
- Pulmonary, Allergy, and Critical Care Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, United States(3).
| | - Stephen Garoff
- Department of Physics, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2).
| | - Todd M Przybycien
- Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2); Department of Βiomedical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2).
| | - Robert D Tilton
- Department of Chemical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2); Department of Βiomedical Engineering, Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, United States(2).
| |
Collapse
|
10
|
Stammitti-Scarpone A, Acosta EJ. Solid-Liquid-Liquid Wettability of Surfactant-Oil-Water Systems and Its Prediction around the Phase Inversion Point. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:4305-4318. [PMID: 30821467 DOI: 10.1021/acs.langmuir.8b03907] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Surfactant-oil-water (SOW) systems are important for numerous applications, including hard surface cleaning, detergency, and enhanced oil-recovery applications. There is limited literature on the wettability of solid-liquid-liquid (SLL) systems around the surfactant phase inversion point (PIP), and the few references that exist point to wettability inversion accompanying the microemulsion (μE) phase inversion. Despite the significance of this phenomenon and the extreme changes in contact angles, there are no models to predict SLL wettability as a function of proximity to the PIP. Recent works on SLL wettability in surfactant-free systems suggest that SLL contact angles can be predicted with an extension of Neumann's equation of state (e-EQS) if the interfacial tension (IFT or γo-w) is known and if there is a good estimate for the interfacial energy between the wetting phase and the surface (γS-wetting liquid). In this work, IFT predictions for SOW systems around the PIP were obtained via the combined hydrophilic-lipophilic difference (HLD) and net-average-curvature (NAC) framework. To test the hypothesis that the combined HLD-NAC + e-EQS can predict wettability inversion around the PIP, with a given γS-μE, the contact angles (measured through the light oil phase, θO) for the μE of sodium dihexyl sulfosuccinate-toluene-saline water system were measured on high surface free energy (SFE) materials (glass, stainless steel, and mica) and on polytetrafluoroethylene (low SFE) around the PIP. Considering that at the PIP, most systems have a contact angle of 90°, an estimated γS-μE = 1/4γo-w@PIP was found to be suitable for the systems considered in this work and for systems presented in the literature. The largest deviations between the predictions and the experimental values were found in the positive HLD range (surfactant in the light oil phase). Although there is room for improvement, this framework can estimate the wetting behavior of SOW systems starting solely from formulation parameters.
Collapse
Affiliation(s)
- Aurelio Stammitti-Scarpone
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario , M5S3E5 , Canada
| | - Edgar J Acosta
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario , M5S3E5 , Canada
| |
Collapse
|
11
|
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.
Collapse
|
12
|
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.
Collapse
|
13
|
Truszkowska D, Henrich F, Schultze J, Koynov K, Räder H, Butt HJ, Auernhammer G. Forced dewetting dynamics of high molecular weight surfactant solutions. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2016.07.073] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
|
14
|
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.
Collapse
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.
| |
Collapse
|
15
|
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.
Collapse
Affiliation(s)
- Rolf E Isele-Holder
- Aachener Verfahrenstechnik, Molecular Simulations and Transformations, RWTH Aachen University, Schinkelstraße 2, 52062 Aachen, Germany.
| | | | | |
Collapse
|
16
|
Lobanova O, Avendaño C, Lafitte T, Müller EA, Jackson G. SAFT-γ force field for the simulation of molecular fluids: 4. A single-site coarse-grained model of water applicable over a wide temperature range. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1004804] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
17
|
Theodorakis PE, Müller EA, Craster RV, Matar OK. Superspreading: mechanisms and molecular design. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:2304-2309. [PMID: 25658859 DOI: 10.1021/la5044798] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The intriguing ability of certain surfactant molecules to drive the superspreading of liquids to complete wetting on hydrophobic substrates is central to numerous applications that range from coating flow technology to enhanced oil recovery. Despite significant experimental efforts, the precise mechanisms underlying superspreading remain unknown to date. Here, we isolate these mechanisms by analyzing coarse-grained molecular dynamics simulations of surfactant molecules of varying molecular architecture and substrate affinity. We observe that for superspreading to occur, two key conditions must be simultaneously satisfied: the adsorption of surfactants from the liquid-vapor surface onto the three-phase contact line augmented by local bilayer formation. Crucially, this must be coordinated with the rapid replenishment of liquid-vapor and solid-liquid interfaces with surfactants from the interior of the droplet. This article also highlights and explores the differences between superspreading and conventional surfactants, paving the way for the design of molecular architectures tailored specifically for applications that rely on the control of wetting.
Collapse
Affiliation(s)
- Panagiotis E Theodorakis
- Department of Chemical Engineering and ‡Department of Mathematics, Imperial College London , South Kensington Campus, SW7 2AZ London, United Kingdom
| | | | | | | |
Collapse
|