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Kanduč M, Schneck E, Netz RR. Understanding the "Berg limit": the 65° contact angle as the universal adhesion threshold of biomatter. Phys Chem Chem Phys 2024; 26:713-723. [PMID: 38100091 DOI: 10.1039/d3cp05084j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2024]
Abstract
Surface phenomena in aqueous environments such as long-range hydrophobic attraction, macromolecular adhesion, and even biofouling are predominantly influenced by a fundamental parameter-the water contact angle. The minimal contact angle required for these and related phenomena to occur has been repeatedly reported to be around 65° and is commonly referred to as the "Berg limit." However, the universality of this specific threshold across diverse contexts has remained puzzling. In this perspective article, we aim to rationalize the reoccurrence of this enigmatic contact angle. We show that the relevant scenarios can be effectively conceptualized as three-phase problems involving the surface of interest, water, and a generic oil-like material that is representative of the nonpolar constituents within interacting entities. Our analysis reveals that attraction and adhesion emerge when substrates display an underwater oleophilic character, corresponding to a "hydrophobicity under oil", which occurs for contact angles above approximately 65°. This streamlined view provides valuable insights into macromolecular interactions and holds implications for technological applications.
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Affiliation(s)
- Matej Kanduč
- Department of Theoretical Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
| | - Emanuel Schneck
- Department of Physics, Technische Universität Darmstadt, Hochschulstrasse 8, Darmstadt 64289, Germany
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany
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2
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Jimidar ISM, Kwiecinski W, Roozendaal G, Kooij ES, Gardeniers HJGE, Desmet G, Sotthewes K. Influence of Wettability and Geometry on Contact Electrification between Nonionic Insulators. ACS APPLIED MATERIALS & INTERFACES 2023; 15:42004-42014. [PMID: 37389550 PMCID: PMC10485807 DOI: 10.1021/acsami.3c05729] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 06/20/2023] [Indexed: 07/01/2023]
Abstract
Contact electrification is an interfacial process in which two surfaces exchange electrical charges when they are in contact with one another. Consequently, the surfaces may gain opposite polarity, inducing an electrostatic attraction. Therefore, this principle can be exploited to generate electricity, which has been precisely done in triboelectric nanogenerators (TENGs) over the last decades. The details of the underlying mechanisms are still ill-understood, especially the influence of relative humidity (RH). Using the colloidal probe technique, we convincingly show that water plays an important role in the charge exchange process when two distinct insulators with different wettability are contacted and separated in <1 s at ambient conditions. The charging process is faster, and more charge is acquired with increasing relative humidity, also beyond RH = 40% (at which TENGs have their maximum power generation), due to the geometrical asymmetry (curved colloid surface vs planar substrate) introduced in the system. In addition, the charging time constant is determined, which is found to decrease with increasing relative humidity. Altogether, the current study adds to our understanding of how humidity levels affect the charging process between two solid surfaces, which is even enhanced up to RH = 90% as long as the curved surface is hydrophilic, paving the way for designing novel and more efficient TENGs, eco-energy harvesting devices which utilize water and solid charge interaction mechanism, self-powered sensors, and tribotronics.
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Affiliation(s)
- Ignaas S. M. Jimidar
- Department
of Chemical Engineering, Vrije Universiteit
Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- Mesoscale
Chemical Systems, MESA+ Institute for Nanotechnology and Faculty of
Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Wojciech Kwiecinski
- Physics
of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Gijs Roozendaal
- Physics
of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - E. Stefan Kooij
- Physics
of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Han J. G. E. Gardeniers
- Mesoscale
Chemical Systems, MESA+ Institute for Nanotechnology and Faculty of
Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Gert Desmet
- Department
of Chemical Engineering, Vrije Universiteit
Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Kai Sotthewes
- Physics
of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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3
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Eriksson M, Claesson PM, Järn M, Wallqvist V, Tuominen M, Kappl M, Teisala H, Vollmer D, Schoelkopf J, Gane PAC, Mäkelä JM, Swerin A. Effects of liquid surface tension on gas capillaries and capillary forces at superamphiphobic surfaces. Sci Rep 2023; 13:6794. [PMID: 37100810 PMCID: PMC10133270 DOI: 10.1038/s41598-023-33875-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 04/20/2023] [Indexed: 04/28/2023] Open
Abstract
The formation of a bridging gas capillary between superhydrophobic surfaces in water gives rise to strongly attractive interactions ranging up to several micrometers on separation. However, most liquids used in materials research are oil-based or contain surfactants. Superamphiphobic surfaces repel both water and low-surface-tension liquids. To control the interactions between a superamphiphobic surface and a particle, it needs to be resolved whether and how gas capillaries form in non-polar and low-surface-tension liquids. Such insight will aid advanced functional materials development. Here, we combine laser scanning confocal imaging and colloidal probe atomic force microscopy to elucidate the interaction between a superamphiphobic surface and a hydrophobic microparticle in three liquids with different surface tensions: water (73 mN m-1), ethylene glycol (48 mN m-1) and hexadecane (27 mN m-1). We show that bridging gas capillaries are formed in all three liquids. Force-distance curves between the superamphiphobic surface and the particle reveal strong attractive interactions, where the range and magnitude decrease with liquid surface tension. Comparison of free energy calculations based on the capillary menisci shapes and the force measurements suggest that under our dynamic measurements the gas pressure in the capillary is slightly below ambient.
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Affiliation(s)
- Mimmi Eriksson
- RISE Research Institutes of Sweden, 11486, Stockholm, Sweden
- Division of Surface and Corrosion Science, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 10044, Stockholm, Sweden
| | - Per M Claesson
- Division of Surface and Corrosion Science, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 10044, Stockholm, Sweden
| | - Mikael Järn
- RISE Research Institutes of Sweden, 11486, Stockholm, Sweden
| | | | - Mikko Tuominen
- RISE Research Institutes of Sweden, 11486, Stockholm, Sweden
| | - Michael Kappl
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, 55128, Mainz, Germany
| | - Hannu Teisala
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, 55128, Mainz, Germany
| | - Doris Vollmer
- Department of Physics at Interfaces, Max Planck Institute for Polymer Research, 55128, Mainz, Germany
| | | | - Patrick A C Gane
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, 00076, Aalto, Finland
- Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000, Belgrade, Serbia
| | - Jyrki M Mäkelä
- Physics Unit, Aerosol Physics Laboratory, Tampere University, 33014, Tampere, Finland
| | - Agne Swerin
- Division of Surface and Corrosion Science, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, 10044, Stockholm, Sweden.
- Department of Engineering and Chemical Sciences, Karlstad University, 65188, Karlstad, Sweden.
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4
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Nagy N. Capillary Bridges on Hydrophobic Surfaces: Analytical Contact Angle Determination. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6201-6208. [PMID: 35523001 PMCID: PMC9118539 DOI: 10.1021/acs.langmuir.2c00674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/28/2022] [Indexed: 06/14/2023]
Abstract
The capillary bridge probe method was introduced previously as a high-accuracy contact angle determination method relying on capillary bridges on hydrophilic and superhydrophilic surfaces [Nagy, N. Langmuir 2019, 35 (15), 5202-5212]. In this work, the behavior of r-ϑ type liquid bridges was studied and the contact angles were determined on hydrophobic surfaces. The equilibrium shape of these liquid bridges often does not contain the neck or haunch region. The unknown neck/haunch radius prevents analytical evaluation of the capillary bridge shape. In this work, the possible incomplete liquid bridge shapes were classified and a novel procedure was developed for the Delaunay's analytical solution-based evaluation of these states. The parameter space of the capillary bridges was visualized and described without using dimensionless variables. As a demonstration, Cyclo Olefin Polymer and PTFE surfaces were investigated, with advancing and receding contact angles determined and compared to the results of sessile drop measurements.
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Shek ACM, Semprebon C, Panter JR, Kusumaatmaja H. Capillary Bridges on Liquid-Infused Surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:908-917. [PMID: 33395301 DOI: 10.1021/acs.langmuir.0c03220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We numerically study two-component capillary bridges formed when a liquid droplet is placed in between two liquid-infused surfaces (LIS). In contrast to commonly studied one-component capillary bridges on noninfused solid surfaces, two-component liquid bridges can exhibit a range of different morphologies where the liquid droplet is directly in contact with two, one, or none of the LIS substrates. In addition, the capillary bridges may lose stability when compressed due to the envelopment of the droplet by the lubricant. We also characterize the capillary force, maximum separation, and effective spring force and find that they are influenced by the shape and size of the lubricant ridge. Importantly, these can be tuned to increase the effective capillary adhesion strength by manipulating the lubricant pressure, Neumann angle, and wetting contact angles. As such, LIS are not only "slippery" parallel to the surface, but they are also "sticky" perpendicular to the surface.
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Affiliation(s)
- Alvin C M Shek
- Department of Physics, Durham University, Durham DH1 3LE, U.K
| | - Ciro Semprebon
- Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, U.K
| | - Jack R Panter
- Department of Physics, Durham University, Durham DH1 3LE, U.K
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7
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Li M, Shi L, Wang X. Physical mechanisms behind the wet adhesion: From amphibian toe-pad to biomimetics. Colloids Surf B Biointerfaces 2021; 199:111531. [PMID: 33383551 DOI: 10.1016/j.colsurfb.2020.111531] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 12/01/2020] [Accepted: 12/06/2020] [Indexed: 10/22/2022]
Abstract
Some amphibians, such as tree frogs, torrent frogs, newts, are able to climb or attach to wet slippery smooth surfaces, even in a vertical or overhanging state, by their reliable reversible adhesions developed on the epidermal of toe pads. It is widely believed that such outstanding function originates from the possible factors of the specialized evolutions of surficial micro/nanostructures, the chemical components of secreted mucus, the solid-liquid behavior of epidermal and the bulk softness of toe pads. In this review, we summarize the main physical mechanisms of these factors behaving underlying the wet adhesion of toe pads from the researches on biological models to artificial counterparts. The discussion of the organism attachments, the interfacial physical forces and the switchable strategies for artificial wet adhesion are also included. The paper gives a deeply, comprehensively understanding of the characters of wet adhesives on amphibians, which performs necessarily for the new strategies of exploring artificial adhesive surfaces.
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Affiliation(s)
- Meng Li
- School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China; International Science and Technology Cooperation Base for Intelligent Equipment Manufacturing in Special Service Environment, Ma'anshan, 243032, China; Anhui Province Key Laboratory of Special and Heavy Load Robot, Ma'anshan, 243032, China
| | - Liping Shi
- School of Mechanical Engineering, Anhui University of Technology, Ma'anshan, 243032, China; International Science and Technology Cooperation Base for Intelligent Equipment Manufacturing in Special Service Environment, Ma'anshan, 243032, China; Anhui Province Key Laboratory of Special and Heavy Load Robot, Ma'anshan, 243032, China.
| | - Xiaolei Wang
- College of Mechanical & Electrical Engineering, Nanjing University of Aeronautics & Astronautics, Nanjing, 210016, China.
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Shahriyari F, Janmaleki M, Sharifi S, Hesar ME, Hoshian S, Taghiabadi R, Razaghian A, Ghadiri M, Peirovi A, Mahmoudi M, Nezhad AS, Khademhosseini A. Effect of cell imprinting on viability and drug susceptibility of breast cancer cells to doxorubicin. Acta Biomater 2020; 113:119-129. [PMID: 32525052 DOI: 10.1016/j.actbio.2020.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 05/30/2020] [Accepted: 06/02/2020] [Indexed: 02/07/2023]
Abstract
This study demonstrates the effect of substrate's geometrical cues on viability and the efficacy of an anti-cancer drug, doxorubicin (DOX), on breast cancer cells. It is hypothesized that the surface topographical properties can mediate the cellular drug intake. Pseudo-three dimensional (3D) platforms were fabricated using imprinting technique from polydimethylsiloxane (PDMS) and gelatin methacryloyl (GelMA) hydrogel to recapitulate topography of cells' membranes. The cells exhibited higher viability on the cell-imprinted platforms for both PDMS and GelMA materials compared to the plain/flat counterparts. For instance, MCF7 cells showed a higher metabolic activity (11.9%) on MCF7-imprinted PDMS substrate than plain PDMS. The increased metabolic activity for the imprinted GelMA was about 44.2% compared to plain hydrogel. The DOX response of cells was monitored for 24 h. Although imprinted substrates demonstrated enhanced biocompatibility, the cultured cells were more susceptible to the drug compared to the plain substrates. In particular, MCF7 cells on imprinted PDMS and GelMA substrates showed 37% and 50% higher in cell death compared to the corresponding plain PDMS and GelMA, respectively. Interestingly, the drug susceptibility of the cells on the imprinted hydrogel was about 70% higher than the cells cultured on imprinted PDMS substrates. Having MCF7 cell-imprinted substrates, DOX responses of two other breast cancer cell lines, SKBR3 and ZR-75-1, were also evaluated. The results support that cell membrane curvature developed by multiscale topography is able to mediate intracellular signaling and drug intake. STATEMENT OF SIGNIFICANCE: Research in biological sciences and drug discovery mostly rely on two dimensional (2D) cell culture techniques which cannot provide a reliable physiologically relevant environment. Lack of extracellular matrix and a large shift in physicochemical properties of conventional 2D substrates can induce aberrant cellular behaviors. While chemical composition, topographical, and mechanical properties of substrates have remarkable impacts on drug susceptibility, gene expression, and protein synthesis, the most cell culture plates are from rigid and plain substrates. A number of (bio)polymeric 3D-platforms have been introduced to resemble innate cell microenvironment. However, their intricate culture protocols restrain their applications in demanding high-throughput drug screening. To address the above concerns, in the present study, a hydrogel-based pseudo-3D substrate with imprinted cell features has been introduced.
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9
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Dai Q, Chong Z, Huang W, Wang X. Migration of Liquid Bridges at the Interface of Spheres and Plates with an Imposed Thermal Gradient. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6268-6276. [PMID: 32397716 DOI: 10.1021/acs.langmuir.9b03951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this paper, we experimentally investigate the migration of liquid bridges at the interface of spheres and plates with an imposed thermal gradient. The key influencing factors of interface gap, sphere material and diameter, liquid viscosity, and thermal gradient on the migration behaviors are highlighted. Furthermore, the physical mechanism of this intriguing interfacial phenomenon is numerically unraveled. The originality of this work lies in the fact that when thermal gradients were encountered, liquid bridges could migrate at the interface of spheres and plates, and a general design philosophy of related parameters for enhancing or weakening this thermal flow is proposed.
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Affiliation(s)
- Qingwen Dai
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China
| | - Zhejun Chong
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China
| | - Wei Huang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China
| | - Xiaolei Wang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China
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10
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Moghadam A, Vahedi Tafreshi H. On liquid bridge adhesion to fibrous surfaces under normal and shear forces. Colloids Surf A Physicochem Eng Asp 2020. [DOI: 10.1016/j.colsurfa.2020.124473] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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11
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Stark AY, Mitchell CT. Stick or Slip: Adhesive Performance of Geckos and Gecko-Inspired Synthetics in Wet Environments. Integr Comp Biol 2019; 59:214-226. [PMID: 30873552 DOI: 10.1093/icb/icz008] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The gecko adhesive system has inspired hundreds of synthetic mimics principally focused on replicating the strong, reversible, and versatile properties of the natural system. For geckos native to the tropics, versatility includes the need to remain attached to substrates that become wet from high humidity and frequent rain. Paradoxically, van der Waals forces, the principal mechanism responsible for gecko adhesion, reduce to zero when two contacting surfaces separate even slightly by entrapped water layers. A series of laboratory studies show that instead of slipping, geckos maintain and even improve their adhesive performance in many wet conditions (i.e., on wet hydrophobic substrates, on humid substrates held at low temperatures). The mechanism for this is not fully clarified, and likely ranges in scale from the chemical and material properties of the gecko's contact structures called setae (e.g., setae soften and change surface confirmation when exposed to water), to their locomotor biomechanics and decision-making behavior when encountering water on a substrate in their natural environment (e.g., some geckos tend to run faster and stop more frequently on misted substrates than dry). Current work has also focused on applying results from the natural system to gecko-inspired synthetic adhesives, improving their performance in wet conditions. Gecko-inspired synthetic adhesives have also provided a unique opportunity to test hypotheses about the natural system in semi-natural conditions replicated in the laboratory. Despite many detailed studies focused on the role of water and humidity on gecko and gecko-inspired synthetic adhesion, there remains several outstanding questions: (1) what, if any, role does capillary or capillary-like adhesion play on overall adhesive performance of geckos and gecko-inspired synthetics, (2) how do chemical and material changes at the surface and in the bulk of gecko setae and synthetic fibrils change when exposed to water, and what does this mean for adhesive performance, and (3) how much water do geckos encounter in their native environment, and what is their corresponding behavioral response? This review will detail what we know about gecko adhesion in wet environments, and outline the necessary next steps in biological and synthetic system investigations.
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Affiliation(s)
- Alyssa Y Stark
- Department of Biology, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085, USA
| | - Christopher T Mitchell
- Department of Biology, Villanova University, 800 East Lancaster Avenue, Villanova, PA 19085, USA
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Aziz H, Tafreshi HV. Competing forces on a liquid bridge between parallel and orthogonal dissimilar fibers. SOFT MATTER 2019; 15:6967-6977. [PMID: 31432863 DOI: 10.1039/c9sm00489k] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This paper presents a detailed investigation on the mechanical forces acting on a liquid bridge between dissimilar fibers in parallel and orthogonal configurations. These forces were measured experimentally, using a sensitive scale, and were also predicted computationally, via numerical simulation. Special attention was paid to the fiber-fiber spacing at which the liquid bridge detached from the fibers, and to how a transition from an equilibrium liquid bridge to a spontaneously (time-dependent) detaching bridge took place. It was found that, while varying the spacing between the fibers affects a liquid bridge differently for fibers with different relative angles with respect to one another, the spacing at which the bridge detaches from the fibers is independent of the fibers' relative angle. This paper also formulates the contribution of the geometrical and wetting properties of the fibers competing for the droplet that results from a liquid bridge detachment, and presents a mathematical expression to predict the fate of that droplet.
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Affiliation(s)
- Hossain Aziz
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284-3015, USA.
| | - Hooman V Tafreshi
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, Virginia 23284-3015, USA.
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Nagy N. Contact Angle Determination on Hydrophilic and Superhydrophilic Surfaces by Using r-θ-Type Capillary Bridges. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:5202-5212. [PMID: 30916567 DOI: 10.1021/acs.langmuir.9b00442] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
To avoid the restrictions of the captive bubble and the Wilhelmy plate techniques, a method was introduced for contact angle measurements under equilibrium conditions. It enables to determine even ultralow contact angles with high precision without prewetting the investigated surface because in this case, the capillary bridge of the test liquid is formed from a pendant drop and used as a probe. The contact angle is determined from the measured capillary force and liquid bridge geometry by using Delaunay's analytical solution. The method was experimentally proved to be valid. As a demonstration, contact angles less than 1° were measured with the uncertainty down to 0.1° on lightly corroded glass surfaces. Moreover, a new observation was obtained in complete wetting situations: the receding contact line starts to advance again during the increase of the bridge length. The contact angle is much lower in this readvancing phase compared to the advancing and receding values because the contact line finds prewetted surface in front of itself. Further advantage of the method is that the existing contact angle goniometers can be developed further into the presented measurement setup.
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Affiliation(s)
- Norbert Nagy
- Institute of Technical Physics and Materials Science , HAS Centre for Energy Research , P.O. Box 49, H-1525 Budapest , Hungary
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14
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Li M, Dai Q, Jiao Q, Huang W, Wang X. Magnetically stimulating capillary effect for reversible wet adhesions. SOFT MATTER 2019; 15:2817-2825. [PMID: 30869733 DOI: 10.1039/c9sm00270g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Despite fascinating natural examples of switchable adhesives to wet surfaces, strategies for an artificially switching capillary adhesion system in situ remains a challenge. Here, we develop a smart reversible magnetic fluid (MF) meniscus adhesion system whose capillary effect can be regulated by external magnetic stimuli. It is revealed that the MF filled joint between two solid surfaces undergoes alteration of its adhesive properties in response to the external stimulus of a varying magnetic field. Compared with the original capillary force (without stimuli), the stimulated one increases or decreases depending on the distributions of applied magnetic field intensities, allowing for switchable adhesive behavior. In addition to the Laplace pressure, hydrostatic pressure induced by the intensity difference in the magnetic field between the inner and outer surfaces of the meniscus was found to contribute to wet adhesion, which accounted for the reversibility. Theoretical models of reversible adhesions have been built and solved as well, and agree well with the experiment results. Our findings not only provide a deep understanding of MF capillary adhesion, but also provide a new method to design reversible wet adhesion systems.
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Affiliation(s)
- Meng Li
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
| | - Qingwen Dai
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
| | - Qing Jiao
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
| | - Wei Huang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
| | - Xiaolei Wang
- National Key Laboratory of Science and Technology on Helicopter Transmission, Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China.
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15
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Soori T, Ward T. Evaporation and instability of an unbounded-axisymmetric liquid bridge between chemically similar and different substrates. J Colloid Interface Sci 2019; 539:45-53. [PMID: 30576987 DOI: 10.1016/j.jcis.2018.12.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/04/2018] [Accepted: 12/05/2018] [Indexed: 11/16/2022]
Abstract
HYPOTHESIS In this manuscript we examine the stability of an evaporating-unbounded axisymmetric liquid bridge confined between parallel-planar similar or chemically different substrates using both theory and experiments. With a quasistatic assumption we use hydrostatics to estimate the minimum stable volume Vmin via the Young-Laplace equation for Bond numbers 0⩽Bo⩽1, and top/bottom wall contact angles 5°<θ<175° although the primary focus is on wetting and partial wetting fluids. Solving the Young-Laplace equation requires knowledge of appropriate capillary pressure values, which appear as a constant, and may not provide unique solution. To examine uniqueness of numerical solutions and volume minima determined from the Young-Laplace equation for unbounded-axisymmetric liquid bridges we analyzed capillary pressure for large and small liquid volume-asymptotic limits at zero Bond number. EXPERIMENTS Experiments were performed to compare with the volume minima calculations for Bond numbers 0.04⩽Bo⩽0.65. Three substrates of varying surface energy were used, with purified water as the primary liquid. Volume estimates and contact angle data were extracted via image analysis and evaporation rates measured from this data are reported. FINDINGS Volume minima were in the range 0.1<Vmin<20 μl depending on Bond number. There was good agreement when comparing predicted volume minima and those determined from experiments for the range of parameters studied.
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Affiliation(s)
- Tejaswi Soori
- Department of Aerospace Engineering, Iowa State University Ames, IA 50011-2271, United States
| | - Thomas Ward
- Department of Aerospace Engineering, Iowa State University Ames, IA 50011-2271, United States
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16
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Nguyen PV, Ho VA. Mechanics of wet adhesion in soft interaction with patterned morphology. BIOINSPIRATION & BIOMIMETICS 2018; 14:016005. [PMID: 30421724 DOI: 10.1088/1748-3190/aaeb09] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Locking surfaces with a wet interface can enhance interactions between a grasped object and a soft pad. This paper presents a mechanical approach to understanding the role of morphological design in achieving wet adhesion for secure grasping by a soft pad. Two conditions were compared in modeling wet interfaces between an object and a soft pad: a pad with a flat surface, and a pad with a micropatterned surface. The latter was designed and analyzed based on the wet attachment between the surface of a tree-frog's toes and its substrate. In this model, we proposed a method to estimate the contact force in both normal and tangential directions between a soft pad with a micropattern surface and a rigid flat surface substrate. A square mold containing 3600 85 μm × 85 μm cells interspaced by grooves 15 μm wide and 15 μm deep was fabricated, using e-beam technology, as the micropattern pad. The generated normal and tangential contact forces of the pad with a micropattern surface, and a pad with a flat surface were measured in both normal and tangential directions under wet conditions. Experimental results showed good agreement with theoretical results, indicating that the micropattern significantly enhanced the contact force of the pad by approximately two-fold for the normal and 1.2- to 1.4-fold for the tangential force. This theoretical approach can be potentially utilized to investigate the association of soft pad morphology with wet adhesion, and enhance efficient grasping by soft robotic hands in wet and high-moisture environments.
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Affiliation(s)
- Pho Van Nguyen
- Soft Haptics Lab, Japan Advanced Institute of Science and Technology (JAIST), Ishikawa, Japan
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17
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Al-Jumaili A, Bazaka K, Jacob MV. Retention of Antibacterial Activity in Geranium Plasma Polymer Thin Films. NANOMATERIALS 2017; 7:nano7090270. [PMID: 28902134 PMCID: PMC5618381 DOI: 10.3390/nano7090270] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 09/05/2017] [Accepted: 09/05/2017] [Indexed: 01/21/2023]
Abstract
Bacterial colonisation of biomedical devices demands novel antibacterial coatings. Plasma-enabled treatment is an established technique for selective modification of physicochemical characteristics of the surface and deposition of polymer thin films. We investigated the retention of inherent antibacterial activity in geranium based plasma polymer thin films. Attachment and biofilm formation by Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was significantly reduced on the surfaces of samples fabricated at 10 W radio frequency (RF) power, compared to that of control or films fabricated at higher input power. This was attributed to lower contact angle and retention of original chemical functionality in the polymer films fabricated under low input power conditions. The topography of all surfaces was uniform and smooth, with surface roughness of 0.18 and 0.69 nm for films fabricated at 10 W and 100 W, respectively. Hardness and elastic modules of films increased with input power. Independent of input power, films were optically transparent within the visible wavelength range, with the main absorption at ~290 nm and optical band gap of ~3.6 eV. These results suggest that geranium extract-derived polymers may potentially be used as antibacterial coatings for contact lenses.
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Affiliation(s)
- Ahmed Al-Jumaili
- Electronics Materials Lab, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.
| | - Kateryna Bazaka
- Electronics Materials Lab, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.
- School of Chemistry, Physics, Mechanical Engineering, Queensland University of Technology, Brisbane, QLD 4000, Australia.
| | - Mohan V Jacob
- Electronics Materials Lab, College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.
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18
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Cadirov N, Booth JA, Turner KL, Israelachvili JN. Influence of Humidity on Grip and Release Adhesion Mechanisms for Gecko-Inspired Microfibrillar Surfaces. ACS APPLIED MATERIALS & INTERFACES 2017; 9:14497-14505. [PMID: 28398039 DOI: 10.1021/acsami.7b01624] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Geckos have developed foot pads that allow them to maintain their unique climbing ability despite vast differences of surfaces and environments, from dry desert to humid rainforest. Likewise, successful gecko-inspired mimics should exhibit adhesive and frictional performance across a similarly diverse range of climates. In this work, we focus on the effect of relative humidity (RH) on the "frictional-adhesion" behavior of gecko-inspired adhesive pads. A surface forces apparatus was used to quantitatively measure adhesion and friction forces of a microfibrillar cross-linked polydimethylsiloxane surface against a smooth hemispherical glass disk at varying relative humidity, from 0 to 100% (including fully submerged under water). Geometrically anisotropic tilted half-cylinder microfibers yield a "grip state" (high adhesion and friction forces after shearing along the tilt of the fibers, Fad+ and F∥+) and a "release state" (low adhesion and friction after shearing against the tilt of the fibers, Fad- and F∥-). By appropriate control of the loading path, this allows for transition between strong attachment and easy detachment. Changing the preload and shear direction gives rise to differences in the effective contact area at each fiber and the microscale and nanoscale structure of the contact while changing the relative humidity results in differences in the relative contributions of van der Waals and capillary forces. In combination, both effects lead to interesting trends in the adhesion and friction forces. At up to 75% RH, the grip state adhesion force remains constant and the ratio of grip to release adhesion force does not drop below 4.0. In addition, the friction forces F∥+ and F∥- and the release state adhesion force Fad- exhibit a maximum at intermediate relative humidity between 40% and 75%.
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Affiliation(s)
- Nicholas Cadirov
- Department of Chemical Engineering, and ‡Department of Mechanical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Jamie A Booth
- Department of Chemical Engineering, and ‡Department of Mechanical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Kimberly L Turner
- Department of Chemical Engineering, and ‡Department of Mechanical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Jacob N Israelachvili
- Department of Chemical Engineering, and ‡Department of Mechanical Engineering, University of California , Santa Barbara, California 93106, United States
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19
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Giltinan J, Diller E, Sitti M. Programmable assembly of heterogeneous microparts by an untethered mobile capillary microgripper. LAB ON A CHIP 2016; 16:4445-4457. [PMID: 27766322 DOI: 10.1039/c6lc00981f] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
At the sub-millimeter scale, capillary forces enable robust and reversible adhesion between biological organisms and varied substrates. Current human-engineered mobile untethered micromanipulation systems rely on forces which scale poorly or utilize gripper-part designs that promote manipulation. Capillary forces, alternatively, are dependent upon the surface chemistry (which is scale independent) and contact perimeter, which conforms to the part surface. We report a mobile capillary microgripper that is able to pick and place parts of various materials and geometries, and is thus ideal for microassembly tasks that cannot be accomplished by large tethered manipulators. We achieve the programmable assembly of sub-millimeter parts in an enclosed three-dimensional aqueous environment by creating a capillary bridge between the targeted part and a synthetic, untethered, mobile body. The parts include both hydrophilic and hydrophobic components: hydrogel, kapton, human hair, and biological tissue. The 200 μm untethered system can be controlled with five-degrees-of-freedom and advances progress towards autonomous desktop manufacturing for tissue engineering, complex micromachines, microfluidic devices, and meta-materials.
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Affiliation(s)
- Joshua Giltinan
- Max-Planck Institute for Intelligent Systems, 70569 Stuttgart, Germany. and Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Eric Diller
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, M5S 3G8 Canada
| | - Metin Sitti
- Max-Planck Institute for Intelligent Systems, 70569 Stuttgart, Germany. and Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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20
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Cheng S, Robbins MO. Nanocapillary Adhesion between Parallel Plates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:7788-95. [PMID: 27413872 DOI: 10.1021/acs.langmuir.6b02024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Molecular dynamics simulations are used to study capillary adhesion from a nanometer scale liquid bridge between two parallel flat solid surfaces. The capillary force, Fcap, and the meniscus shape of the bridge are computed as the separation between the solid surfaces, h, is varied. Macroscopic theory predicts the meniscus shape and the contribution of liquid/vapor interfacial tension to Fcap quite accurately for separations as small as two or three molecular diameters (1-2 nm). However, the total capillary force differs in sign and magnitude from macroscopic theory for h ≲ 5 nm (8-10 diameters) because of molecular layering that is not included in macroscopic theory. For these small separations, the pressure tensor in the fluid becomes anisotropic. The components in the plane of the surface vary smoothly and are consistent with theory based on the macroscopic surface tension. Capillary adhesion is affected by only the perpendicular component, which has strong oscillations as the molecular layering changes.
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Affiliation(s)
- Shengfeng Cheng
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute, Virginia Polytechnic Institute and State University , Blacksburg, Virginia 24061, United States
| | - Mark O Robbins
- Department of Physics and Astronomy, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States
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21
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Zhuang J, Ju YS. A Combined Experimental and Numerical Modeling Study of the Deformation and Rupture of Axisymmetric Liquid Bridges under Coaxial Stretching. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:10173-10182. [PMID: 26323057 DOI: 10.1021/acs.langmuir.5b02102] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The deformation and rupture of axisymmetric liquid bridges being stretched between two fully wetted coaxial disks are studied experimentally and theoretically. We numerically solve the time-dependent Navier-Stokes equations while tracking the deformation of the liquid-air interface using the arbitrary Lagrangian-Eulerian (ALE) moving mesh method to fully account for the effects of inertia and viscous forces on bridge dynamics. The effects of the stretching velocity, liquid properties, and liquid volume on the dynamics of liquid bridges are systematically investigated to provide direct experimental validation of our numerical model for stretching velocities as high as 3 m/s. The Ohnesorge number (Oh) of liquid bridges is a primary factor governing the dynamics of liquid bridge rupture, especially the dependence of the rupture distance on the stretching velocity. The rupture distance generally increases with the stretching velocity, far in excess of the static stability limit. For bridges with low Ohnesorge numbers, however, the rupture distance stay nearly constant or decreases with the stretching velocity within certain velocity windows due to the relative rupture position switching and the thread shape change. Our work provides an experimentally validated modeling approach and experimental data to help establish foundation for systematic further studies and applications of liquid bridges.
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Affiliation(s)
- Jinda Zhuang
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles , 420 Westwood Plaza, Los Angeles, California 90095, United States
| | - Y Sungtaek Ju
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles , 420 Westwood Plaza, Los Angeles, California 90095, United States
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22
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Mastrangeli M. The Fluid Joint: The Soft Spot of Micro- and Nanosystems. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2015; 27:4254-4272. [PMID: 26129857 DOI: 10.1002/adma.201501260] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 05/03/2015] [Indexed: 06/04/2023]
Abstract
Fluid bridges are ubiquitous soft structures of finite size that conform to and link the surfaces of neighboring objects. Fluid joints, the specific type of fluid bridge with at least one extremity constrained laterally, display even more pronounced reactivity and self-restoration, which make them remarkably suited for assembly, actuation, and manipulation purposes. Their peculiar surface and bulk properties place fluid joints at the rich intersection of diverse scientific interests, and foster their widespread use throughout micro- and nanotechnology. A critical survey of the mechanics and of the manifold applications of fluid bridges and joints in micro- and nanosystems is presented here, along with current challenges and multidisciplinary perspectives.
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Affiliation(s)
- Massimo Mastrangeli
- Bio, Electro And Mechanical Systems, Université Libre de Bruxelles, Avenue F. D. Roosevelt 50, CP 165/56, 1050, Bruxelles, Belgium
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23
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Sauret A, Boulogne F, Soh B, Dressaire E, Stone HA. Wetting morphologies on randomly oriented fibers. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:62. [PMID: 26123768 DOI: 10.1140/epje/i2015-15062-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 05/01/2015] [Accepted: 05/18/2015] [Indexed: 06/04/2023]
Abstract
We characterize the different morphologies adopted by a drop of liquid placed on two randomly oriented fibers, which is a first step toward understanding the wetting of fibrous networks. The present work reviews previous modeling for parallel and touching crossed fibers and extends it to an arbitrary orientation of the fibers characterized by the tilting angle and the minimum spacing distance. Depending on the volume of liquid, the spacing distance between fibers and the angle between the fibers, we highlight that the liquid can adopt three different equilibrium morphologies: 1) a column morphology in which the liquid spreads between the fibers, 2) a mixed morphology where a drop grows at one end of the column or 3) a single drop located at the node. We capture the different morphologies observed using an analytical model that predicts the equilibrium configuration of the liquid based on the geometry of the fibers and the volume of liquid.
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Affiliation(s)
- Alban Sauret
- Surface du Verre et Interfaces, UMR 125, 93303, Aubervilliers, France.
| | - François Boulogne
- Department of Mechanical and Aerospace Engineering, Princeton University, 08544, Princeton, NJ, USA
| | - Beatrice Soh
- Department of Mechanical and Aerospace Engineering, Princeton University, 08544, Princeton, NJ, USA
| | - Emilie Dressaire
- Department of Mechanical and Aerospace Engineering, New York University Polytechnic School of Engineering, 11201, Brooklyn, NY, USA
| | - Howard A Stone
- Department of Mechanical and Aerospace Engineering, Princeton University, 08544, Princeton, NJ, USA
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24
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Cremaldi JC, Khosla T, Jin K, Cutting D, Wollman K, Pesika N. Interaction of oil drops with surfaces of different interfacial energy and topography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3385-3390. [PMID: 25723337 DOI: 10.1021/acs.langmuir.5b00051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
During a marine oil spill, the oil can interact with and potentially wet a variety of surfaces such as corals, skin/shells of marine animals, and bird feathers. We present both qualitative and quantitative data for the interaction of a dodecane droplet submerged in water with surfaces varying in both surface energy and roughness. Flat, unstructured silicon surfaces with water in air contact angles of 0°, 43°, 66°, 87°, 96°, and 108° were tested first to obtain base readings, after which photolithography was used to introduce structured surfaces representative of marine biological systems. We find that the more hydrophilic a surface, the less prone it is to oil contamination. Also, the Cassie-Baxter approximation holds up for submerged oil in water systems and can be used to predict contact angles of oil on solid rough surfaces submerged in an aqueous environment. Furthermore, the addition of surface structure, even on strongly hydrophobic (oleophilic) surfaces, greatly reduced (≈75% reduction in F(adhesion)) a surface's affinity for oil.
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Affiliation(s)
- Joseph C Cremaldi
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Tushar Khosla
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Kejia Jin
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
- ‡Intralox, New Orleans, Louisiana 70123, United States
| | - David Cutting
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
- §Koch International, Witchita, Kansas 67220, United States
| | - Kristen Wollman
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
| | - Noshir Pesika
- †Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, United States
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25
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Abstract
We report the preparation of millimeter-scale particles by thermal polymerization of liquid monomer capillary bridges to form catenoid-shaped particles that exhibit negative Gaussian curvature. The shape of the capillary bridges and resulting particles can be finely tuned using several addressable parameters: (i) the shape, size, and orientation of lithographic pinning features on the spanned surfaces; (ii) the distance between opposing support surfaces; and (iii) the lateral displacement (shear) of opposing features. The catenoid-shaped particles exhibit controllable optical properties as a result of their concave menisci, the shape of which can be easily manipulated. The particles self assemble in the presence of a condensing liquid (water) to form reversible neck-to-neck pairs and less reversible end-to-end aggregates. We argue that this approach could be scaled down to micrometer dimensions by fabricating an array of micrometer-scale particles. We also argue, with a discussion of dynamic wetting, that these particles will exhibit interesting anisotropic adhesive properties.
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26
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Soltannia B, Sameoto D. Strong, reversible underwater adhesion via gecko-inspired hydrophobic fibers. ACS APPLIED MATERIALS & INTERFACES 2014; 6:21995-22003. [PMID: 25454841 DOI: 10.1021/am5075375] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Strong, reversible underwater adhesion using gecko-inspired surfaces is achievable through the use of a hydrophobic structural material and does not require surface modification or suction cup effects for this adhesion to be effective. Increased surface energy can aid in dry adhesion in an air environment but strongly degrades wet adhesion via reduction of interfacial energy underwater. A direct comparison of structurally identical but chemically different mushroom shaped fibers shows that strong, reversible adhesion, even in a fully wetted, stable state, is feasible underwater if the structural material of the fibers is hydrophobic and the mating surface is not strongly hydrophilic. The exact adhesion strength will be a function of the underwater interfacial energy between surfaces and the specific failure modes of individual fibers. This underwater adhesion has been calculated to be potentially greater than the dry adhesion for specific combinations of hydrophobic surfaces.
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Affiliation(s)
- Babak Soltannia
- Department of Mechanical Engineering, University of Alberta , 4-9, Mechanical Engineering Building, Edmonton, Alberta T6G 2G8, Canada
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27
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Watanabe H, Fujimoto A, Takahara A. Surface functionalization by decal-like transfer of thermally cross-linked urushiol thin films. ACS APPLIED MATERIALS & INTERFACES 2014; 6:18517-18524. [PMID: 25314021 DOI: 10.1021/am5052284] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have demonstrated surface functionalization through the decal-like transfer of thermally cross-linked urushiol thin films onto various substrates. Tensile adhesive strength measurements showed that the film adheres strongly to the surface of various substrates including chemically inert materials, such as polyolefins and thermosetting resins, because of the properties of urushiol. Furthermore, the highly cross-linked structure of urushiol made the films mechanically robust. These two properties allowed the fabrication of practicable thin films for indirect surface modification. Actually, the robust thin film served as a scaffold for an Au thin film, which was then bound to various substrates. Surface-texturing of nanodecal was also demonstrated as an application aspects.
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Affiliation(s)
- Hirohmi Watanabe
- Japan Science and Technology Agency (JST), ERATO Takahara Soft Interfaces Project, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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28
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Peisker H, Heepe L, Kovalev AE, Gorb SN. Comparative study of the fluid viscosity in tarsal hairy attachment systems of flies and beetles. J R Soc Interface 2014; 11:20140752. [PMID: 25142527 PMCID: PMC4233759 DOI: 10.1098/rsif.2014.0752] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Accepted: 07/28/2014] [Indexed: 11/12/2022] Open
Abstract
Wet adhesive systems of insects strongly rely for their function on the formation of capillary bridges with the substrate. Studies on the chemical composition and evaporation dynamics of tarsal secretions strongly suggest a difference in chemistry of secretion in beetles and flies, both possessing hairy attachment devices. This difference is assumed to influence the viscosity of the secretion. Here, we applied a microrheological technique, based on the immersion of nanometric beads in the collected tarsal footprints, to estimate secretion viscosity in a beetle (Coccinella septempunctata) and a fly (Calliphora vicina). Both species studied possess distinct differences in viscosity, the median of which was calculated as 21.8 and 10.9 mPa s, respectively. We further present an approximate theoretical model to calculate the contact formation time of spatula-like terminal contact elements using the viscosity data of the covering fluid. The estimated contact formation time is proportional to the tarsal secretion viscosity and to the square of the contact radius of the contact element.
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Affiliation(s)
- Henrik Peisker
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany
| | - Lars Heepe
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany
| | - Alexander E Kovalev
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany
| | - Stanislav N Gorb
- Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, 24118 Kiel, Germany
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29
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Dutka F, Napiórkowski M. The influence of van der Waals forces on droplet morphological transitions and solvation forces in nanochannels. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:035101. [PMID: 24285307 DOI: 10.1088/0953-8984/26/3/035101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The morphological phase transition between sessile and lenticular shapes of a droplet placed in a nanochannel is observed upon increasing the droplet volume. The phase diagram for this system is discussed within both macroscopic and mesoscopic approaches. On the mesoscopic level, the van der Waals forces are taken into account via the effective interface potential acting between the channel walls and the droplet. We discuss the contact angle dependence on the droplet volume and the distance between the walls; this angle turns out to be smaller than the macroscopic Young's angle. The droplet's presence induces the solvation force acting between the channel walls. It can be either attractive or repulsive, depending on the width of the channel.
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Affiliation(s)
- F Dutka
- Institute of Physical Chemistry, Polish Academy of Sciences, ulica Kasprzaka 44/52, 01-224 Warszawa, Poland
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30
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Grohmann C, Blankenstein A, Koops S, Gorb SN. Attachment of Galerucella nymphaeae (Coleoptera, Chrysomelidae)to surfaces with different surface energy. J Exp Biol 2014; 217:4213-20. [DOI: 10.1242/jeb.108902] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Numerous studies deal with insect attachment on surfaces with different roughness, however, little is known about insect attachment on surfaces with different chemistry. In the present study, we describe attachment structures of the water-lily leaf beetle Galerucella nymphaeae (Linnaeus, 1758) and test the hypothesis that larval and adult stages can generate strongest attachment on surfaces with contact angles that are similar to those of leaves of their host plants. The larvae bear a smooth attachment system with arolium-like structures at their legs and a pygopodium at the abdomen tip. Adults have pointed setae on the ventral side of the two proximal tarsomeres and densely arranged spatula-shaped ones on their third tarsomere. In a centrifugal force tester, larvae and adults attained highest friction forces and safety factors on surfaces with a water contact angle of 83° compared to those of 6, 26 and 109°. This comes close to the contact angle of their host plant Nuphar lutea (86°). The similarity of larval and adult performances might be a result of a similar chemical composition of their attachment fluid. We compare our findings with previous studies on the forces insects generate on surfaces with different surface energies.
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31
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Wang Y, Michielsen S, Lee HJ. Symmetric and asymmetric capillary bridges between a rough surface and a parallel surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:11028-11037. [PMID: 23915184 DOI: 10.1021/la401324f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Although the formation of a capillary bridge between two parallel surfaces has been extensively studied, the majority of research has described only symmetric capillary bridges between two smooth surfaces. In this work, an instrument was built to form a capillary bridge by squeezing a liquid drop on one surface with another surface. An analytical solution that describes the shape of symmetric capillary bridges joining two smooth surfaces has been extended to bridges that are asymmetric about the midplane and to rough surfaces. The solution, given by elliptical integrals of the first and second kind, is consistent with a constant Laplace pressure over the entire surface and has been verified for water, Kaydol, and dodecane drops forming symmetric and asymmetric bridges between parallel smooth surfaces. This solution has been applied to asymmetric capillary bridges between a smooth surface and a rough fabric surface as well as symmetric bridges between two rough surfaces. These solutions have been experimentally verified, and good agreement has been found between predicted and experimental profiles for small drops where the effect of gravity is negligible. Finally, a protocol for determining the profile from the volume and height of the capillary bridge has been developed and experimentally verified.
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Affiliation(s)
- Yongxin Wang
- College of Textiles, North Carolina State University, 2401 Research Drive, Raleigh, North Carolina 27695-8301, USA
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32
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You S, Wan MP. Mathematical models for the van der Waals force and capillary force between a rough particle and surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:9104-9117. [PMID: 23802940 DOI: 10.1021/la401516m] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The capability of predicting the adhesion forces between a rough particle and surface including the van der Waals force and capillary force is important for modeling various processes involving particle surface retention and resuspension. On the basis of the fractal theory describing the behavior of multiple roughness scales and the Gaussian roughness distribution, a set of mathematical models for the van der Waals force and capillary force is proposed. The proposed models provide the adhesion force predictions in good agreement with the existing experimental data and converge to the previous classical solutions of the adhesion forces between a smooth particle and surface as the roughness goes to zero. The influences of roughness for the combination of particle and surface, relative humidity (RH), contact angle, and Hurst exponent toward the adhesion forces are examined using the proposed models. The decline mode of the adhesion force with surface roughness and contact angle, as well as the increase mode with RH and the Hurst exponent are reasonably predicted by the proposed models. The comparison between the proposed models and those from the existing studies is also performed, which shows the similarities and differences between the proposed models and the existing models.
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Affiliation(s)
- Siming You
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798 Singapore
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33
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Kusumaatmaja H, Wales DJ. Defect motifs for constant mean curvature surfaces. PHYSICAL REVIEW LETTERS 2013; 110:165502. [PMID: 23679616 DOI: 10.1103/physrevlett.110.165502] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 12/13/2012] [Indexed: 06/02/2023]
Abstract
The energy landscapes of electrostatically charged particles embedded on constant mean curvature surfaces are analyzed for a wide range of system size, curvature, and interaction potentials. The surfaces are taken to be rigid, and the basin-hopping method is used to locate the putative global minimum structures. The defect motifs favored by potential energy agree with experimental observations for colloidal systems: extended defects (scars and pleats) for weakly positive and negative Gaussian curvatures, and isolated defects for strongly negative Gaussian curvatures. Near the phase boundary between these regimes, the two motifs are in strong competition, as evidenced from the appearance of distinct funnels in the potential energy landscape. We also report a novel defect motif consisting of pentagon pairs.
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Affiliation(s)
- Halim Kusumaatmaja
- University Chemical Laboratories, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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Broesch DJ, Frechette J. From concave to convex: capillary bridges in slit pore geometry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15548-15554. [PMID: 23061424 DOI: 10.1021/la302942k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We investigate the morphological evolution of nonaxisymmetric capillary bridges in slit-pore geometry as the height of the pore and aspect ratio of the bridge are varied. The liquid bridges are formed between two hydrophobic surfaces patterned with hydrophilic strips. The aspect ratio of the capillary bridges (length/width) is varied from 2.5 to 120 by changing the separation between the surfaces, the width of the strips, or the fluid volume. As the bridge height is increased, the aspect ratio decreases and we observe a large increase in the mean curvature of the bridge. More specifically, the following counterintuitive result is observed: the mean curvature of the bridges changes sign and goes from negative (concave bridge) to positive (convex bridge) when the height is increased at constant volume. These experimental observations are in quantitative agreement with Surface Evolver simulations. Scaling shows a collapse of the data indicating that this transition in the sign of the Laplace pressure is universal for capillary bridges with high aspect ratios. Finally, we show that the morphology diagrams obtained from our 3D analysis are considerably different from those expected from a 2D analysis.
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Affiliation(s)
- David J Broesch
- Chemical and Biomolecular Engineering Department, Johns Hopkins University, Baltimore, Maryland 21218, United States
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35
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Zeng X, He M, Li H, Wang J, Song Y, Jiang L. Investigating the adhesion of water droplets at low temperatures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14995-14998. [PMID: 22077429 DOI: 10.1021/la2036136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Adhesion of droplets to solid surfaces at low temperatures is crucial for antifogging and antifreezing, etc. So far, most reports on adhesion measurements have been carried out in air-liquid-solid systems, but it remains difficult to precisely investigate the adhesion at low temperatures due to the uncontrollable condensation. On the basis of the liquid-liquid-solid system, a new method to measure the adhesion of water droplets at low temperatures was developed and employed. Moreover, the reported method could be viable in other liquid-liquid-solid systems with wider temperature window; thus, it will find applications in broad fields such as crude oil recovery, ore-dressing, and transfer printing.
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Affiliation(s)
- Xiping Zeng
- Beijing National Laboratory For Molecular Sciences (BNLMS), Laboratory of New Materials, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China
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Srinivasan S, McKinley GH, Cohen RE. Assessing the accuracy of contact angle measurements for sessile drops on liquid-repellent surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:13582-13589. [PMID: 21923173 DOI: 10.1021/la2031208] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Gravity-induced sagging can amplify variations in goniometric measurements of the contact angles of sessile drops on super-liquid-repellent surfaces. The very large value of the effective contact angle leads to increased optical noise in the drop profile near the solid-liquid free surface and the progressive failure of simple geometric approximations. We demonstrate a systematic approach to determining the effective contact angle of drops on super-repellent surfaces. We use a perturbation solution of the Bashforth-Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height. The results and analysis can be represented in terms of a dimensionless Bond number that depends on the maximum drop width and the capillary length of the liquid to quantify the extent of gravity-induced sagging. Finally, we illustrate the inherent sensitivity of goniometric contact angle measurement techniques to drop dimensions as the apparent contact angle approaches 180°.
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Affiliation(s)
- Siddarth Srinivasan
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Men Y, Zhang X, Wang W. Rupture kinetics of liquid bridges during a pulling process: a kinetic density functional theory study. J Chem Phys 2011; 134:124704. [PMID: 21456692 DOI: 10.1063/1.3570657] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Capillary bridge is a common phenomenon in nature and can significantly contribute to the adhesion of biological and artificial micro- and nanoscale objects. Especially, it plays a crucial role in the operation of atomic force microscopy (AFM) and influences in the measured force. In the present work, we study the rupture kinetics and transition pathways of liquid bridges connecting an AFM tip and a flat substrate during a process of pulling the tip off. Depending on thermodynamic conditions and the tip velocity, two regimes corresponding to different transition pathways are identified. In the single-bridge regime, the initial equilibrium bridge persists as a single one during the pulling process until the liquid bridge breaks. While, in the multibridge regime the stretched liquid bridge transforms into an intermediate state with a collection of slender liquid bridges, which then break gradually during the pulling process. Moreover, the critical rupture distance at which the bridges break changes with the tip velocity and thermodynamic conditions, and its maximum value occurs near the boundary between the single-bridge regime and the multibridge regime, where the longest range capillary force is produced. In this work, the effects of tip velocity, tip size, tip-fluid interaction, and humidity on rupture kinetics and transition pathways are also systematically studied.
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Affiliation(s)
- Yumei Men
- Division of Molecular and Materials Simulation, Key Laboratory for Nanomaterials, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029, China
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Dodds S, Carvalho MS, Kumar S. Stretching liquid bridges with bubbles: the effect of air bubbles on liquid transfer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:1556-1559. [PMID: 21210674 DOI: 10.1021/la104369z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Liquid bridges containing bubbles are relevant to industrial printing and are also a topic of fundamental scientific interest. We use flow visualization to study the stretching of liquid bridges, both with and without bubbles, at low capillary numbers. We find that whereas the breakup of wetting fluids between two identical surfaces is symmetric about the bridge midpoint, contact line pinning breaks this symmetry at slow stretching speeds for nonwetting fluids. We exploit this observation to force air bubbles selectively toward the least hydrophilic plate confining the liquid bridge.
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Affiliation(s)
- Shawn Dodds
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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Boesel LF, Greiner C, Arzt E, del Campo A. Gecko-inspired surfaces: a path to strong and reversible dry adhesives. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2010; 22:2125-37. [PMID: 20349430 DOI: 10.1002/adma.200903200] [Citation(s) in RCA: 214] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The amazing adhesion of gecko pads to almost any kind of surfaces has inspired a very active research direction over the last decade: the investigation of how geckos achieve this feat and how this knowledge can be turned into new strategies to reversibly join surfaces. This article reviews the fabrication approaches used so far for the creation of micro- and nanostructured fibrillar surfaces with adhesive properties. In the light of the pertinent contact mechanics, the adhesive properties are presented and discussed. The decisive design parameters are fiber radius and aspect ratio, tilt angle, hierarchical arrangement and the effect of the backing layer. Also first responsive systems that allow thermal switching between nonadhesive and adhesive states are described. These structures show a high potential of application, providing the remaining issues of robustness, reliability, and large-area manufacture can be solved.
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Fabié L, Durou H, Ondarçuhu T. Capillary forces during liquid nanodispensing. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:1870-1878. [PMID: 20099921 DOI: 10.1021/la902614s] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present a comprehensive study of the capillary force measured during the liquid nanodispensing of attoliter droplets with an atomic force microscope tip. Due to the presence of a nanochannel drilled at the tip apex and connected to a reservoir droplet deposited on the cantilever, we observe a large variety of force curves during the deposition process. We propose a numerical method which accounts for most of the experimental observations. In particular, we clearly demonstrate the influence of the nanochannel diameter. This study leads to a better understanding of the mechanisms of liquid transfer from the tip to the surface and also provides a real time monitoring of the dispensing. Besides these applications, the method we use, which can handle a large variety of conditions and also complex geometries, may find a wide range of applications.
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Affiliation(s)
- Laure Fabié
- Nanosciences group, CEMES-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse cedex 4, France
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Virozub A, Haimovich N, Brandon S. Three-dimensional simulations of liquid bridges between two cylinders: forces, energies, and torques. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:12837-12842. [PMID: 19852478 DOI: 10.1021/la902578j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We present numerical simulations of three-dimensional liquid bridges between two identical smooth and chemically homogeneous cylinders held at a fixed distance and angle one with respect to the other. Despite the limited range of parameters studied, an analysis of resultant forces, energies, and torques reveals a rich level of detail. For large enough separations between the cylinders, the bridges appear symmetric and stable in shape and are found to yield a negligible torque on the cylinders. The force of adhesion is found to be positive in this case (the cylinders are attracted one to the other). A reduction in the distance between the cylinders reveals different behavior depending on the particular value of the set of parameters considered. For example, it appears that while relatively low contact angle systems favor attractive (positive) forces and stable symmetric bridges for small separation distances, larger contact angles lead to the coexistence of stable asymmetric and (apparently) unstable symmetric solutions, mostly (and respectively) associated with near-zero and negative (repulsive) forces of adhesion. In addition, while the larger values of contact angles studied here (90 degrees, 110 degrees) are associated with barely detectable torques, smaller values of contact angle are found to be associated with torques acting to rotate cylinders into a position where they are parallel one with respect to the other.
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De Souza EJ, Kamperman M, Castellanos G, Kroner E, Armbruester V, Romann MS, Schick B, Arzt E. In vitro adhesion measurements between skin and micropatterned poly(dimethylsiloxane) surfaces. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2009:6018-6021. [PMID: 19964886 DOI: 10.1109/iembs.2009.5334532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Micropatterned adhesive surfaces may have potential in reconstructive surgery. The adhesion performance of mice ear skin to micropatterned poly(dimethylsiloxane) (PDMS) was investigated, under in vitro conditions, and compared to flat substrates. No significant difference in separation force F was observed between flat substrates and micropatterned surfaces with pillar arrays. However, the energy necessary for separation of the substrate from the skin was sensitive to the topography. Furthermore, our results show that the force-displacement curves depended on the wetness of the skin: Highest force values were obtained for fresh skin while the forces decreased as the skin dried out. The results are encouraging for further studies on the potential of patterned PDMS in biomedical applications.
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Affiliation(s)
- E J De Souza
- INM, Leibniz-Institut für Neue Materialien gGmbH, Campus D2, 2D-66123 Saarbrücken, Germany.
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