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Fardin MA, Hautefeuille M, Sharma V. Dynamic duos: the building blocks of dimensional mechanics. SOFT MATTER 2024. [PMID: 38920374 DOI: 10.1039/d4sm00263f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Mechanics studies the relationships between space, time, and matter. These relationships can be expressed in terms of the dimensions of length , time , and mass . Each dimension broadens the scope of mechanics. Historically, mechanics emerged from geometry, which considers quantities like lengths or areas, with dimensions of the form . With the Renaissance, quantities combining space and time were considered, like speed, acceleration and later diffusivity, all of the form . Eventually, mechanics reached its full potential by including "mass-carrying" quantities such as mass, force, momentum, energy, action, power, viscosity, etc. These standard mechanical quantities have dimensions of the form where x and y are integers. In this contribution, we show that, thanks to this dimensional structure, these mass-carrying quantities can be readily arranged into a table such that x and y increase along the row and column, respectively. Ratios of quantities in the same rows provide characteristic lengths, while those in the same columns yield characteristic times, encompassing a great variety of physical phenomena from atomic to astronomical scales. Most generally, we show that selecting duos of mechanical quantities that are neither on the same row nor column of the table yields dynamics, where one mechanical quantity is understood as impelling motion, while the other impedes it. The force and the mass are the prototypes of impelling and impeding factors, but many other duos are possible. We present examples from the physical and biological realms, including planetary motion, sedimentation, explosions, fluid flows, turbulence, diffusion, cell mechanics, capillary and gravity waves, and spreading, pinching, and coalescence of drops and bubbles. This review provides a novel synthesis revealing the power of scaling or dimensional analysis, to understand processes governed by the interplay of two mechanical quantities. This elementary decomposition of space, time and motion into pairs of mechanical factors is the foundation of "dimensional mechanics", a method that this review wishes to promote and advance. Pairs are the fundamental building blocks, but they are only a starting point. Beyond this simple world of mechanical duos, we envision a richer universe that beckons with an interplay of three, four, or more quantities, yielding multiple characteristic lengths, times, and kinematics. This review is complemented by online video lectures, which initiate a discussion on the elaborate interplay of two or more mechanical quantities.
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Affiliation(s)
- Marc A Fardin
- CNRS, Institut Jacques Monod, Université de Paris, F-75013 Paris, France.
- The Academy of Bradylogists, France
| | - Mathieu Hautefeuille
- Institut de Biologie Paris Seine, UMR 7622, Sorbonne Université, 7 quai Saint Bernard, 75005 Paris, France
| | - Vivek Sharma
- The Academy of Bradylogists, France
- Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinois 60608, USA
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Tiwari A, Lee SJ, Garg DK, Shin S, Thokchom AK. Characterizing the Microparticles Deposition Structure and its Photonic Nature in Surfactant-Laden Evaporating Colloidal Sessile Droplets. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:8711-8720. [PMID: 38608175 DOI: 10.1021/acs.langmuir.4c00596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2024]
Abstract
This work presents a simple method to create photonic microstructures via the natural evaporation of surfactant-laden colloidal sessile droplets on a flat substrate. In the absence of dissolved surfactant, the evaporating colloidal droplet forms a well-known coffee ring deposition. In contrast, the presence of surfactant leads to the formation of multiple ring structures due to the repetitive pinning-depinning behavior of the droplet contact line (CL). It is found that the multiring structure shows vibrant iridescent structural colors while the coffee ring lacks a photonic nature. This difference in the structural color for the presence and absence of the surfactant is found to be dependent on the arrangement of the particles in the deposition structure. The particle arrangement in the multirings is monolayered and well-ordered. The ordering of the particles is strongly influenced by the particle dynamics, contact angle (CA), and CL dynamics of the evaporating colloidal solution droplet. Furthermore, the iridescent nature of the multiring deposition is demonstrated and explained. The dependence of the multiring deposition structure on the concentration of the dissolved surfactant and the suspended particles is also studied. The findings demonstrate that an intermediate surfactant concentration is desirable for the formation of a multiring structure. Further, the pinning-depinning CL dynamics that causes the formation of the multiring deposition structure is discussed. Finally, we demonstrate the applicability of the approach to smaller droplet volumes.
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Affiliation(s)
- Appurva Tiwari
- Soft Matter Lab, Department of Chemical Engineering, Shiv Nadar Institution of Eminence Deemed to be University, Greater Noida 201314, India
| | - Seong Jae Lee
- Department of Polymer Engineering, The University of Suwon, Hwaseong, Gyeonggi 18323, South Korea
| | - Dhiraj Kumar Garg
- Intencity Lab, Department of Chemical Engineering, Shiv Nadar Institution of Eminence Deemed to be University, Greater Noida 201314, India
| | - Sehyun Shin
- Department of Mechanical Engineering, Korea University, Anam Dong, Seoul 02841, South Korea
| | - Ashish Kumar Thokchom
- Soft Matter Lab, Department of Chemical Engineering, Shiv Nadar Institution of Eminence Deemed to be University, Greater Noida 201314, India
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Sun Z, Zhao R, Yu M, Liu Y, Ma Y, Guo X, Gu YC, Formstone C, Xu Y, Wu X. Enhanced dosage delivery of pesticide under unmanned aerial vehicle condition for peanut plant protection: tank-mix adjuvants and formulation improvement. PEST MANAGEMENT SCIENCE 2024; 80:1632-1644. [PMID: 37987532 DOI: 10.1002/ps.7895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 11/16/2023] [Accepted: 11/21/2023] [Indexed: 11/22/2023]
Abstract
BACKGROUND Suspension concentrate (SC) is one of the most widely used formulations for agricultural plant protection. With the rapid development of unmanned aerial vehicle (UAV) plant protection, the problems of spray drift, droplet rebound and poor wettability in the application of SC from UAVs have attracted wide attention. Although some tank-mix adjuvants have been used to enhance dosage delivery for UAV, their effects and mechanisms are not fully clear, and few formulations are specifically designed for UAV. RESULTS The type and concentration of tank-mix adjuvant affect the dosage delivery of SC. MO501 can significantly reduce DV<100μm , and inhibit droplet rebound on peanut leaves at concentrations ≥0.5%. Silwet 408 can achieve complete wetting and superspreading after adding ≥0.2% concentrations, but only ≥0.5% can inhibit rebound. XL-70 shows excellent regulation ability even at low concentration, and 0.2% concentration can simultaneously suppress impact and promote spreading. Besides, the formulation oil dispersion (OD) can significantly reduce the driftable fine fraction and inhibit rebound at dilution ratios of ≤250-fold, thus enhancing dosage delivery. CONCLUSION SC is prone to rebound on hydrophobic leaf surfaces and shows poor wetting and spreading properties. Appropriate types and concentrations of tank-mix adjuvants and formulation improvement are two effective strategies for improving the dosage delivery of pesticides, whereas the addition of inappropriate adjuvants may cause potential risks instead. These findings provide guidance for the rational selection of tank-mix adjuvants and potential applications of OD for UAV plant protection. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Zhe Sun
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Rui Zhao
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Meng Yu
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Yabo Liu
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Yingjian Ma
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Xinyu Guo
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Yu-Cheng Gu
- Syngenta Jealott's Hill International Research Centre, Bracknell, UK
| | - Carl Formstone
- Syngenta Jealott's Hill International Research Centre, Bracknell, UK
| | - Yong Xu
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
| | - Xuemin Wu
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing, China
- Key Laboratory of National Forestry and Grassland Administration on Pest Chemical Control, China Agricultural University, Beijing, China
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Li Y, Chen Y, Li Y, Stone HA, Pahlavan AA, Granick S. Volatile Droplets on Water are Sculpted by Vigorous Marangoni-Driven Subphase Flow. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:16272-16283. [PMID: 37948043 DOI: 10.1021/acs.langmuir.3c01678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
The shapes of highly volatile oil-on-water droplets become strongly asymmetric when they are out of equilibrium. The unsaturated organic vapor atmosphere causes evaporation and leads to a strong Marangoni flow in the bath, unlike that previously seen in the literature. Inspecting these shapes experimentally on millisecond and submillimeter time and length scales and theoretically by scaling arguments, we confirm that Marangoni-driven convection in the subphase mechanically stresses the droplet edges to an extent that increases for organic droplets of smaller contact angle and accordingly smaller thickness. The viscous stress generated by the subphase overcomes the thermodynamic Laplace pressure. The oil droplets develop copious regularly spaced fingers, and these fingers develop spike-shaped and branched treelike structures. Unlike this behavior for single-component (surfactant-free) oil droplets, droplets composed of two miscible (surfactant-free) organic liquids develop a rim of the less volatile component along the droplet perimeter, from which jets of monodisperse smaller droplets eject periodically due to the Rayleigh-Plateau instability. When evaporation shrinks droplets to μm size, their shapes fluctuate chaotically, and ellipsoidal shapes rupture into smaller daughter droplets when subphase convection flow pulls them in opposite directions. The shape of the evaporating oil droplets is kneaded and sculpted by vigorous flow in the water subphase.
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Affiliation(s)
- Yitan Li
- Center for Soft and Living Matter, Institute for Basic Science (IBS), Ulsan 44919, South Korea
| | - Yuguang Chen
- College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Yan Li
- College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Amir A Pahlavan
- Department of Mechanical Engineering and Material Science, Yale University, New Haven, Connecticut 06511, United States
| | - Steve Granick
- Center for Soft and Living Matter, Institute for Basic Science (IBS), Ulsan 44919, South Korea
- Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States
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Wan CQ, Pang YH, Zhai YS, Shen XF. Ratio fluorescence test strip visualized by amino-functionalized metal-organic framework for rapid sensing of glyphosate. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 297:122673. [PMID: 37054567 DOI: 10.1016/j.saa.2023.122673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 03/22/2023] [Accepted: 03/23/2023] [Indexed: 05/14/2023]
Abstract
As glyphosate is a broad-spectrum herbicide extensively used in agriculture worldwide, rapid glyphosate detection is essential for food safety and human health. Herein, a ratio fluorescence test strip was prepared and coupled with an amino-functionalized bismuth-based metal-organic framework (NH2-Bi-MOF) that bonded with copper ion for rapid visualization and determination of glyphosate. NH2-Bi-MOF had excellent fluorescence performance, and the copper ion, a Lewis acid, was selected as the quencher. The strong chelation of glyphosate with copper ion and its quick interaction with NH2-Bi-MOF would turn on the fluorescence signal, thus enabling the quantitative sensing of glyphosate, with a linear range of 0.10-200 µmol L-1, and recoveries between 94.8% and 113.5%. The system was then expanded to a ratio fluorescence test strip, in which the fluorescent ring sticker was set as a binding-in self-calibration to reduce errors from the angle and light dependency. The method realized the visual semi-quantitation referring to a standard card, as well as the ratio quantitation using the gray value output with LOD of 0.82 µmol L-1. And the as-developed test strip was accessible, portable, and reliable, thus offering a platform for the rapid on-site detection of glyphosate and other residual pesticides.
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Affiliation(s)
- Chao-Qun Wan
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Yue-Hong Pang
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Yong-Shun Zhai
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
| | - Xiao-Fang Shen
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
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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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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.
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Fan JY, Liu ZX, Rao J, Yan K, Chen Z, Ran Y, Yan B, Yao J, Lu G, Zhu H, Li CZ, Chen H. High-Performance Organic Solar Modules via Bilayer-Merged-Annealing Assisted Blade Coating. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2110569. [PMID: 35525536 DOI: 10.1002/adma.202110569] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 03/11/2022] [Indexed: 06/14/2023]
Abstract
Although encouraging progress is being made on spin-coated prototype cells, organic solar cells (OSCs) still face significant challenges, yet to be explored, for upscaling the multi-stacked photoactive layers in the construction of large-area modules. Herein, high-performance opaque and semitransparent organic solar modules are developed via a bilayer-merged-annealing (BMA)-assisted blade-coating strategy, achieving impressive efficiencies of 14.79% and 12.01% with respect to active area of 18.73 cm2 , which represent the best organic solar minimodules so far. It is revealed that the BMA strategy effectively resolves the de-wetting issues between polar charge transport layer solution and non-polar bulk heterojunction blends, hence improving the film coverage, along with electronic and electric contacts of multi-stacked photoactive layers. As result, organic solar modules coated under ambient conditions successfully retain the high-efficiency of small-area cells upon 312 times area scaling-up. Overall, this work provides a facile and effective method to fabricate high-performance organic solar modules under ambient conditions.
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Affiliation(s)
- Jing-Yuan Fan
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Zhi-Xi Liu
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Jack Rao
- Hangzhou Microquanta Semiconductor Co. LTD., Hangzhou, 310027, P. R. China
| | - Kangrong Yan
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Zeng Chen
- Center for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Yixin Ran
- Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710054, P. R. China
| | - Buyi Yan
- Hangzhou Microquanta Semiconductor Co. LTD., Hangzhou, 310027, P. R. China
| | - Jizhong Yao
- Hangzhou Microquanta Semiconductor Co. LTD., Hangzhou, 310027, P. R. China
| | - Guanghao Lu
- Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, 710054, P. R. China
| | - Haiming Zhu
- Center for Chemistry of High-Performance & Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Chang-Zhi Li
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
| | - Hongzheng Chen
- State Key Laboratory of Silicon Materials, MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, 310027, P. R. China
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Chatterjee S, Murallidharan JS, Bhardwaj R. Size-Dependent Dried Colloidal Deposit and Particle Sorting via Saturated Alcohol Vapor-Mediated Sessile Droplet Spreading. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6128-6147. [PMID: 35507639 DOI: 10.1021/acs.langmuir.2c00492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We experimentally and theoretically investigate a distinct problem of spreading, evaporation, and the associated dried deposits of a colloidal particle-laden aqueous sessile droplet on a surface in a saturated alcohol vapor environment. In particular, the effect of particle size on monodispersed suspensions and efficient self-sorting of bidispersed particles have been investigated. The alcohol vapor diffuses toward the droplet's curved liquid-vapor interface from the far field. The incoming vapor mass flux profile assumes a nonuniform pattern across the interface. The alcohol vapor molecules are adsorbed at the liquid-vapor interface, which eventually leads to absorption into the droplet's liquid phase due to the miscibility. This phenomenon triggers a liquid-vapor interfacial tension gradient and causes a reduction in the global surface tension of the droplet. This results in a solutal Marangoni flow recirculation and spontaneous droplet spreading. The interplay between these phenomena gives rise to a complex internal fluid flow within the droplet, resulting in a significantly modified and strongly particle-size-dependent dried colloidal deposit. While the smaller particles form a multiple ring pattern, larger particles form a single ring, and additional "patchwise" deposits emerge. High-speed visualization of the internal liquid-flow revealed that initially, a ring forms at the first location of the contact line. Concurrently, the Marangoni flow recirculation drives a collection of particles at the liquid-vapor interface to form clusters. Thereafter, as the droplet spreads, the smaller particles in the cluster exhibit a "jetlike" outward flow, forming multiple ring patterns. In contrast, the larger particles tend to coalesce together in the cluster, forming the "patchwise" deposits. The widely different response of the different-sized particles to the internal fluid flow enables an efficient sorting of the smaller particles at the contact line from bidispersed suspensions. We corroborate the measurements with theoretical and numerical models wherever possible.
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Affiliation(s)
- Sanghamitro Chatterjee
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | | | - Rajneesh Bhardwaj
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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Liu W, Kappl M, Steffen W, Butt HJ. Controlling supraparticle shape and structure by tuning colloidal interactions. J Colloid Interface Sci 2021; 607:1661-1670. [PMID: 34592553 DOI: 10.1016/j.jcis.2021.09.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/03/2021] [Accepted: 09/06/2021] [Indexed: 11/25/2022]
Abstract
HYPOTHESIS Assembly of colloids in drying colloidal suspensions on superhydrophobic surface is influenced by the colloidal interactions, which determine the shape and interior structure of the assembled supraparticle. The introduction of salt (electrolyte) into the assembly system is expected to influence the colloid interactions and packing during the evaporation process. Hence, both the outer shape and internal structure of supraparticles should be controlled by varying salt concentrations. EXPERIMENTS Suspensions of electrostatically stabilized polystyrene particles with specified salt concentrations were chosen as model systems to conduct the evaporation on a superhydrophobic surface. A systematic study was performed by regulating the concentration and valency of salt. The morphology and interior of supraparticles were carefully characterized with electron scanning microscopy, while the colloidal interaction was established using colloidal probe atomic force microscopy. FINDINGS Supraparticles displayed a spherical-to-nonspherical shape change due to the addition of salts. The extent of crystallization depended on salt concentration. These changes in shape and structure were correlated with salt-dependent single colloid interaction forces, which were not previously investigated in detail in radially symmetric evaporation geometry. Our findings are crucial for understanding assembly behavior during the drying process and offer guidance for preparing complex supraparticles to meet specific applications requirement.
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Affiliation(s)
- Wendong Liu
- School of Chemical Engineering, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China; Department of Physics at Interfaces, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Michael Kappl
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
| | - Werner Steffen
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
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Nishimura S, Murakami Y. Facile preparation of porous polymeric sheets with different sizes of pores on both sides using spontaneous emulsification. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.126149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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12
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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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