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Godeffroy L, Shkirskiy V, Noël JM, Lemineur JF, Kanoufi F. Fuelling electrocatalysis at a single nanoparticle by ion flow in a nanoconfined electrolyte layer. Faraday Discuss 2023; 246:441-465. [PMID: 37427498 DOI: 10.1039/d3fd00032j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
We explore the possibility of coupling the transport of ions and water in a nanochannel with the chemical transformation of a reactant at an individual catalytic nanoparticle (NP). Such configuration could be interesting for constructing artificial photosynthesis devices coupling the asymmetric production of ions at the catalytic NP, with the ion selectivity of the nanochannels acting as ion pumps. Herein we propose to observe how such ion pumping can be coupled to an electrochemical reaction operated at the level of an individual electrocatalytic Pt NP. This is achieved by confining a (reservoir) droplet of electrolyte to within a few micrometres away from an electrocatalytic Pt NP on an electrode. While the region of the electrode confined by the reservoir and the NP are cathodically polarised, operando optical microscopy reveals the growth of an electrolyte nanodroplet on top of the NP. This suggests that the electrocatalysis of the oxygen reduction reaction operates at the NP and that an electrolyte nanochannel is formed - acting as an ion pump - between the reservoir and the NP. We have described here the optically imaged phenomena and their relevance to the characterization of the electrolyte nanochannel linking the NPs to the electrolyte microreservoir. Additionally, we have addressed the capacity of the nanochannel to transport ions and solvent flow to the NP.
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Affiliation(s)
| | | | - Jean-Marc Noël
- Université Paris Cité, CNRS, ITODYS, F-75013 Paris, France.
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2
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Azimi Yancheshme A, Palmese GR, Alvarez NJ. A generalized scaling theory for spontaneous spreading of Newtonian fluids on solid substrates. J Colloid Interface Sci 2023; 636:677-688. [PMID: 36680958 DOI: 10.1016/j.jcis.2023.01.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 01/03/2023] [Accepted: 01/05/2023] [Indexed: 01/09/2023]
Abstract
HYPOTHESIS There exists a generalized solution for the spontaneous spreading dynamics of droplets taking into account the influence of interfacial tension and gravity. EXPERIMENTS This work presents a generalized scaling theory for the problem of spontaneous dynamic spreading of Newtonian fluids on a flat substrate using experimental analysis and numerical simulations. More specifically, we first validate and modify a dynamic contact angle model to accurately describe the dependency of contact angle on the contact line velocity, which is generalized by the capillary number. The dynamic contact model is implemented into a two-phase moving mesh computational fluid dynamics (CFD) model, which is validated using experimental results. FINDINGS We show that the spreading process is governed by three important parameters: the Bo number, viscous timescale τviscous, and static advancing contact angle, θs. More specifically, there exists a master spreading curve for a specific Bo and θs by scaling the spreading time with the τviscous. Moreover, we developed a correlation for prediction of the equilibrium shape of the droplets as a function of both Bo and θs. The results of this study can be used in a wide range of applications to predict both dynamic and equilibrium shape of droplets, such as in droplet-based additive manufacturing.
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Affiliation(s)
| | - Giuseppe R Palmese
- Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
| | - Nicolas J Alvarez
- Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, USA
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3
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Ivvala J, Arora HS, Grewal HS. Towards Development of Sustainable Metallic Superhydrophobic Materials. Colloids Surf A Physicochem Eng Asp 2023. [DOI: 10.1016/j.colsurfa.2023.131047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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4
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Liu J, Aday X, Wang X, Li Z, Liu J. On demand oil/water separation enabled by microporous ultra-thin aluminum foil with asymmetric wettability. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.129334] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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5
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Burhan AM, Klahan B, Cummins W, Andrés-Guerrero V, Byrne ME, O’Reilly NJ, Chauhan A, Fitzhenry L, Hughes H. Posterior Segment Ophthalmic Drug Delivery: Role of Muco-Adhesion with a Special Focus on Chitosan. Pharmaceutics 2021; 13:1685. [PMID: 34683978 PMCID: PMC8539343 DOI: 10.3390/pharmaceutics13101685] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 09/24/2021] [Accepted: 09/27/2021] [Indexed: 01/04/2023] Open
Abstract
Posterior segment eye diseases (PSEDs) including age macular degeneration (AMD) and diabetic retinopathy (DR) are amongst the major causes of irreversible blindness worldwide. Due to the numerous barriers encountered, highly invasive intravitreal (IVT) injections represent the primary route to deliver drugs to the posterior eye tissues. Thus, the potential of a more patient friendly topical route has been widely investigated. Mucoadhesive formulations can decrease precorneal clearance while prolonging precorneal residence. Thus, they are expected to enhance the chances of adherence to corneal and conjunctival surfaces and as such, enable increased delivery to the posterior eye segment. Among the mucoadhesive polymers available, chitosan is the most widely explored due to its outstanding mucoadhesive characteristics. In this review, the major PSEDs, their treatments, barriers to topical delivery, and routes of topical drug absorption to the posterior eye are presented. To enable the successful design of mucoadhesive ophthalmic drug delivery systems (DDSs), an overview of mucoadhesion, its theory, characterization, and considerations for ocular mucoadhesion is given. Furthermore, chitosan-based DDs that have been explored to promote topical drug delivery to the posterior eye segment are reviewed. Finally, challenges of successful preclinical to clinical translation of these DDSs for posterior eye drug delivery are discussed.
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Affiliation(s)
- Ayah Mohammad Burhan
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
| | - Butsabarat Klahan
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
| | - Wayne Cummins
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
| | - Vanessa Andrés-Guerrero
- Innovation, Therapy and Pharmaceutical Development in Ophthalmology (InnOftal) Research Group, Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Sanitary Research Institute of the San Carlos Clinical Hospital (IdISSC), Complutense University of Madrid, 28040 Madrid, Spain;
| | - Mark E. Byrne
- Biomimetic & Biohybrid Materials, Biomedical Devices & Drug Delivery Laboratories, Department of Biomedical Engineering, Rowan University, Glassboro, NJ 08028, USA;
| | - Niall J. O’Reilly
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
| | - Anuj Chauhan
- Chemical and Biological Engineering Department, Colorado School of Mines, Golden, CO 80401, USA;
| | - Laurence Fitzhenry
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
| | - Helen Hughes
- Ocular Therapeutics Research Group, Pharmaceutical and Molecular Biotechnology Research Centre, Waterford Institute of Technology, X91 K0EK Waterford, Ireland; (W.C.); (N.J.O.); (L.F.); (H.H.)
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6
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Kotb Y, Cagnard A, Houston KR, Khan SA, Hsiao LC, Velev OD. What makes epoxy-phenolic coatings on metals ubiquitous: Surface energetics and molecular adhesion characteristics. J Colloid Interface Sci 2021; 608:634-643. [PMID: 34628322 DOI: 10.1016/j.jcis.2021.09.091] [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: 07/31/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 11/29/2022]
Abstract
HYPOTHESIS Wetting characteristics of epoxy and phenolic resins on metals depend on the molecular interactions between resins' functional groups and metal surface. Those interactions affect the practical adhesion strength of epoxy-phenolic coatings on metals. Estimation of the theoretical adhesion energies can reveal this system's microscopic adhesion mechanisms. EXPERIMENTS Adhesion is estimated theoretically based on resins' wettability on metals, and experimentally through pull-off adhesion testing of cured coatings. The effect of various functional groups on adhesion is decoupled using epoxy and phenolic resins with different functionalities. To assess the impact of the metal passivation on adhesion, tinplated and tin-free steel substrates are used. Differences in their surface chemical composition and polarity are investigated using XPS. FINDINGS Theoretical adhesion results reveal a superior adhesion of epoxy compared to phenolic resins. Moreover, epoxy resins having a higher content of epoxide-to-hydroxyl groups show improved theoretical and practical adhesion. The importance of epoxides in driving resins' initial adhesion on metals is attributed to the formation of direct chemical bonds with active hydrogen on metal surfaces. The adhesion of coatings on tin-free steel is found to be higher than on tinplated steel. This is associated to the increased hydroxyl fraction on tin-free steel surface leading to more hydrogen bonds formation.
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Affiliation(s)
- Yosra Kotb
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | | | | | - Saad A Khan
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Lilian C Hsiao
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Orlin D Velev
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
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Liu T, Kittikunakorn N, Zhang Y, Zhang F. Mechanisms of twin screw melt granulation. J Drug Deliv Sci Technol 2021. [DOI: 10.1016/j.jddst.2020.102150] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Gao J, Low KHJ, Chen Y, Tai ES, Chung T, Drum CL. High recovery, point‐of‐collection plasma separation from blood using electrospun polyacrylonitrile membranes. AIChE J 2020. [DOI: 10.1002/aic.17088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jie Gao
- Department of Chemical and Biomolecular Engineering National University of Singapore Singapore
| | - Kwee Hiang Jackson Low
- Department of Medicine, Yong Loo Lin School of Medicine National University of Singapore Singapore
| | - Yang Chen
- School of Metallurgy and Environment Central South University Changsha China
| | - E. Shyong Tai
- Department of Medicine, Yong Loo Lin School of Medicine National University of Singapore Singapore
| | - Tai‐Shung Chung
- Department of Chemical and Biomolecular Engineering National University of Singapore Singapore
| | - Chester Lee Drum
- Department of Medicine, Yong Loo Lin School of Medicine National University of Singapore Singapore
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Novel Cleaning-in-Place Strategies for Pharmaceutical Hot Melt Extrusion. Pharmaceutics 2020; 12:pharmaceutics12060588. [PMID: 32599822 PMCID: PMC7356020 DOI: 10.3390/pharmaceutics12060588] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 06/17/2020] [Accepted: 06/20/2020] [Indexed: 02/06/2023] Open
Abstract
To avoid any type of cross-contamination, residue-free production equipment is of utmost importance in the pharmaceutical industry. The equipment cleaning for continuous processes such as hot melt extrusion (HME), which has recently gained popularity in pharmaceutical applications, necessitates extensive manual labour and costs. The present work tackles the HME cleaning issue by investigating two cleaning strategies following the extrusion of polymeric formulations of a hormonal drug and for a sustained release formulation of a poorly soluble drug. First, an in-line quantification by means of UV–Vis spectroscopy was successfully implemented to assess very low active pharmaceutical ingredient (API) concentrations in the extrudates during a cleaning procedure for the first time. Secondly, a novel in-situ solvent-based cleaning approach was developed and its usability was evaluated and compared to a polymer-based cleaning sequence. Comparing the in-line data to typical swab and rinse tests of the process equipment indicated that inaccessible parts of the equipment were still contaminated after the polymer-based cleaning procedure, although no API was detected in the extrudate. Nevertheless, the novel solvent-based cleaning approach proved to be suitable for removing API residue from the majority of problematic equipment parts and can potentially enable a full API cleaning-in-place of a pharmaceutical extruder for the first time.
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10
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Spreading of biologically relevant liquids over the laser textured surfaces. J Colloid Interface Sci 2020; 567:224-234. [PMID: 32058172 DOI: 10.1016/j.jcis.2020.02.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 02/02/2020] [Accepted: 02/03/2020] [Indexed: 12/21/2022]
Abstract
HYPOTHESIS The distribution of biological objects upon the spreading of biologically relevant dispersions over laser textured surfaces is affected by the dispersion composition and substrate chemistry and roughness. EXPERIMENTS To examine the role of the substrate texture in biologically relevant liquid spreading, the dynamic behavior of droplets of water and dispersions of bacterial cells and viruses and dynamic behavior of droplet/air surface tension were addressed. A new procedure to simultaneously distinguish three different spreading fronts was developed. FINDINGS The study of spreading of water and the biologically relevant liquids over the laser textured substrate indicate the development of three spreading fronts associated with the movement of bulk droplet base, the flow along the microchannels, and the nanotexture impregnation. The anisotropy of spreading for all types of liquid fronts was found. Despite the expected difference in the rheological behavior of water and the biologically relevant liquids, the spreading of all tested liquids was successfully described by power-law fits. The droplet base spreading for all tested liquids followed the Tanner law. The advancing of water and dispersions in the microchannels along both fast and slow axes was described by Washburn type behavior. The impregnation of the nanotexture by water and biologically relevant liquids demonstrated universality in power fit description with an exponent n = 0.23.
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11
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Rokoni A, Kim DO, Sun Y. Micropattern-controlled wicking enhancement in hierarchical micro/nanostructures. SOFT MATTER 2019; 15:6518-6529. [PMID: 31346591 DOI: 10.1039/c9sm01055f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Wicking in hierarchical micro/nanostructured surfaces has attracted significant attention due to its potential applications in thermal management, moisture capturing, drug delivery, and oil recovery. Although some studies have shown that hierarchical structures enhance wicking over micro-structured surfaces, others have found very limited wicking improvement. In this study, we demonstrate the importance of micropatterns in wicking enhancement in hierarchical surfaces using ZnO nanorods grown on silicon micropillars of varying spacings and heights. The wicking front over hierarchical surfaces is found to follow a two-stage motion, where wicking is faster around micropillars, but slower in between adjacent pillar rows and the latter stage dictates the wicking enhancement in hierarchical surfaces. The competition between the added capillary action and friction due to nanostructures in these two different wicking stages results in a strong dependence of wicking enhancement on the height and spacing of the micropillars. A scaling model for the propagation coefficient is developed for wicking in hierarchical surfaces considering nanostructures in both wicking stages and the model agrees well with the experiments. This microstructure-controlled two-stage wicking characteristic sheds light on a more effective design of hierarchical micro/nanostructured surfaces for wicking enhancement.
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Affiliation(s)
- Arif Rokoni
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104, USA.
| | - Dong-Ook Kim
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104, USA.
| | - Ying Sun
- Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA 19104, USA.
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12
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Prevention of lipid loss from hair by surface and internal modification. Sci Rep 2019; 9:9834. [PMID: 31285480 PMCID: PMC6614367 DOI: 10.1038/s41598-019-46370-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/27/2019] [Indexed: 11/08/2022] Open
Abstract
Surfactants during routine washing have a tremendous effect on lipid loss from hair. This study aims to understand the loss of lipids from hair upon contact with surfactants and develop a way to prevent the lipid loss. The change in lipid levels depends on the relative hydrophobicity of the lipid. We herein propose that the change in lipid levels can be protected by two modifications. In the case of fatty acids and cholesterol (group A), the concentration difference between virgin hair versus surface modified hair with highly charged polymer was 22 to 32% higher after washing with surfactants while the loss of squalene and wax esters (group B) in response to surfactants still occurred even after the surface modification. In the hair treated by internal modification with the carbodiimide reaction, 52.0 to 81.3% more lipids in group B were prevented than in the untreated hair. Finally, different types of lipids were successfully protected by surface and internal modifications from the surfactant treatment. This study will be the basis for understanding the mechanisms by which surfactants damage the lipid barrier of tissues including hair and for establishing strategies to defend the barrier.
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Rongqi S, Qingshun B, Xin H, Aimin Z, Feihu Z. Molecular dynamics simulation of the spreading of the nanosized droplet on a graphene-coated substrate: the effect of the contact line forces. MOLECULAR SIMULATION 2018. [DOI: 10.1080/08927022.2018.1479750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Shen Rongqi
- School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
| | - Bai Qingshun
- School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
| | - He Xin
- School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
| | - Zhang Aimin
- School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
| | - Zhang Feihu
- School of Mechanical and Electrical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
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Shiomoto S, Yamaguchi K, Kobayashi M. Time Evolution of Precursor Thin Film of Water on Polyelectrolyte Brush. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10276-10286. [PMID: 30102545 DOI: 10.1021/acs.langmuir.8b02070] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The microscopic wetting behavior of a water film on the line-patterned surface of a polyelectrolyte brush was directly visualized using an optical microscope by dyeing procedures. Surface line patterns of 5 and 5 μm width or 10 and 5 μm width for the polyelectrolyte brush and hydrophobic monolayer, respectively, were prepared by a photolithography process, chemical vapor adsorption method, and surface-initiated polymerization. A droplet of water containing dye was placed on the line-patterned surface. In front of the contact line, a water film with a nanometer-scale thickness, referred to as a precursor film, elongated along the polymer brush line with time. The elongation velocity at the first stage increased as the brush line width increased. On the other hand, at the second stage after the macroscopic contact line stopped moving, the precursor film continued to elongate in proportion to the 0.6 power of time, independent of the brush thickness, line width, and droplet volume.
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15
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Iwamatsu M. Topography- and topology-driven spreading of non-Newtonian power-law liquids on a flat and a spherical substrate. Phys Rev E 2018; 96:042803. [PMID: 29347502 DOI: 10.1103/physreve.96.042803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Indexed: 11/07/2022]
Abstract
The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids on a flat and a spherical rough and textured substrate is theoretically studied in the capillary-controlled spreading regime. A droplet whose scale is much larger than that of the roughness of substrate is considered. The equilibrium contact angle on a rough substrate is modeled by the Wenzel and the Cassie-Baxter model. Only the viscous energy dissipation within the droplet volume is considered, and that within the texture of substrate by imbibition is neglected. Then, the energy balance approach is adopted to derive the evolution equation of the contact angle. When the equilibrium contact angle vanishes, the relaxation of dynamic contact angle θ of a droplet obeys a power-law decay θ∼t^{-α} except for the Newtonian and the non-Newtonian shear-thinning liquid of the Wenzel model on a spherical substrate. The spreading exponent α of the non-Newtonian shear-thickening liquid of the Wenzel model on a spherical substrate is larger than others. The relaxation of the Newtonian liquid of the Wenzel model on a spherical substrate is even faster showing the exponential relaxation. The relaxation of the non-Newtonian shear-thinning liquid of Wenzel model on a spherical substrate is fastest and finishes within a finite time. Thus, the topography (roughness) and the topology (flat to spherical) of substrate accelerate the spreading of droplet.
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Affiliation(s)
- Masao Iwamatsu
- Department of Physics, Faculty of Liberal Arts and Sciences, Tokyo City University, Setagaya-ku, Tokyo 158-8557, Japan
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16
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Analyzing the Molecular Kinetics of Water Spreading on Hydrophobic Surfaces via Molecular Dynamics Simulation. Sci Rep 2017; 7:10880. [PMID: 28883662 PMCID: PMC5589961 DOI: 10.1038/s41598-017-11350-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Accepted: 08/23/2017] [Indexed: 11/15/2022] Open
Abstract
In this paper, we report molecular kinetic analyses of water spreading on hydrophobic surfaces via molecular dynamics simulation. The hydrophobic surfaces are composed of amorphous polytetrafluoroethylene (PTFE) with a static contact angle of ~112.4° for water. On the basis of the molecular kinetic theory (MKT), the influences of both viscous damping and solid-liquid retarding were analyzed in evaluating contact line friction, which characterizes the frictional force on the contact line. The unit displacement length on PTFE was estimated to be ~0.621 nm and is ~4 times as long as the bond length of C-C backbone. The static friction coefficient was found to be ~\documentclass[12pt]{minimal}
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\begin{document}$${10}^{-3}$$\end{document}10−3 Pa·s, which is on the same order of magnitude as the dynamic viscosity of water, and increases with the droplet size. A nondimensional number defined by the ratio of the standard deviation of wetting velocity to the characteristic wetting velocity was put forward to signify the strength of the inherent contact line fluctuation and unveil the mechanism of enhanced energy dissipation in nanoscale, whereas such effect would become insignificant in macroscale. Moreover, regarding a liquid droplet on hydrophobic or superhydrophobic surfaces, an approximate solution to the base radius development was derived by an asymptotic expansion approach.
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Zhao L, Zhao J, Liu Y, Guo Y, Zhang L, Chen Z, Zhang H, Zhang Z. Continuously Tunable Wettability by Using Surface Patterned Shape Memory Polymers with Giant Deformability. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:3327-3333. [PMID: 27167599 DOI: 10.1002/smll.201600092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Revised: 04/03/2016] [Indexed: 06/05/2023]
Abstract
Designing smart surfaces with tunable wettability has drawn much attention in recent years for academic research and practical applications. Most of the previous methods to achieve such surfaces demand some particular materials that inherently have special features or complicated structures which are usually not easy to obtain. A novel strategy to achieve such smart surfaces is proposed by using the surface patterned shape memory polymers of chemically crosslinked polycyclooctene which shows a giant deformability of up to ≈730% strain. The smart surfaces possess the ability to continuously tune the wettability by controlling the recovery temperature and/or time. Coating the modified titanium dioxide nanoparticles onto such surfaces renders the surface superhydrophobicity and expands the tunable range of contact angles (CAs). Theoretical calculations of the CAs at different strains via modified Cassie model well explain the tunable wettability behaviors of such smart surfaces.
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Affiliation(s)
- Lingyu Zhao
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
- Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
- University of Chinese Academy of Science, Beijing, 100049, China
| | - Jun Zhao
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Yayun Liu
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Yufeng Guo
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Liangpei Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Zhuo Chen
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Hui Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
| | - Zhong Zhang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, China
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