1
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Li H, Asta N, Wang Z, Pettersson T, Wågberg L. Reevaluation of the adhesion between cellulose materials using macro spherical beads and flat model surfaces. Carbohydr Polym 2024; 332:121894. [PMID: 38431407 DOI: 10.1016/j.carbpol.2024.121894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/25/2024] [Accepted: 01/30/2024] [Indexed: 03/05/2024]
Abstract
Interactions between dry cellulose were studied using model systems, cellulose beads, and cellulose films, using custom-built contact adhesion testing equipment. Depending on the configuration of the substrates in contact, Polydimethylsiloxane (PDMS) film, cellulose films spin-coated either on PDMS or glass, the interaction shows three distinct processes. Firstly, molecular interlocking is formed between cellulose and cellulose when there is a soft PDMS thin film backing the cellulose film. Secondly, without backing, no initial attraction force between the surfaces is observed. Thirdly, a significant force increase, ∆F, is observed during the retraction process for cellulose on glass, and there is a maximum in ∆F when the retraction rate is increased. This is due to the kinetics of a contacting process occurring in the interaction zone between the surfaces caused by an interdigitation of a fine fibrillar structure at the nano-scale, whereas, for the spin-coated cellulose surfaces on the PDMS backing, there is a more direct adhesive failure. The results have generated understanding of the interaction between cellulose-rich materials, which helps design new, advanced cellulose-based materials. The results also show the complexity of the interaction between these surfaces and that earlier mechanisms, based on macroscopic material testing, are simply not adequate for molecular tailoring.
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Affiliation(s)
- Hailong Li
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, 116024 Dalian, China; Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden.
| | - Nadia Asta
- Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden
| | - Zhen Wang
- Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden
| | - Torbjörn Pettersson
- Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden; Wallenberg Wood Science Centre, Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, 10044 Stockholm, Sweden.
| | - Lars Wågberg
- Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, SE-100 44 Stockholm, Sweden; Wallenberg Wood Science Centre, Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Teknikringen 56, 10044 Stockholm, Sweden.
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2
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Zhao M, Wu J, Zeng F, Dong Z, Shen X, Hua Z, Liu G. Wetting-enhanced adhesion of photo-polymerized supramolecular adhesives for both smooth and rough surfaces. Chem Sci 2024; 15:6445-6453. [PMID: 38699279 PMCID: PMC11062117 DOI: 10.1039/d4sc01188k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 03/27/2024] [Indexed: 05/05/2024] Open
Abstract
Efficient interactions between an adhesive and a substrate surface at the molecular level are the basis for the formation of robust adhesion, which substantially relies on interfacial wetting. However, strong adhesives usually improve cohesion but compromise interfacial properties. Herein, we have reported a kind of robust supramolecular adhesive based on the outstanding mobility and interfacial wettability of adhesive precursors. In situ fast photopolymerization endows supramolecular adhesives with more outstanding adhesion for both smooth and rough surfaces in air and underwater in contrast to their counterparts from thermal polymerization. In addition to their low viscosity and high monomer concentration, supramolecular adhesive precursors without any organic solvents possess well-defined hydrogen bonding interactions. These superior properties consistently contribute to the wetting of the substrate and the formation of adhesive polymers with high molecular weights. This work highlights that enhancing interfacial wetting between an adhesive and a substrate is a promising route to achieving robust adhesion.
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Affiliation(s)
- Mengyuan Zhao
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Jiang Wu
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Fanxuan Zeng
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Zhi Dong
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Xinyi Shen
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Zan Hua
- The Key Laboratory of Functional Molecular Solids, Ministry of Education, Department of Materials Chemistry, School of Chemistry and Materials Science, Anhui Normal University Wuhu Anhui 214002 China
| | - Guangming Liu
- Department of Chemical Physics, Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
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3
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Sanner A, Kumar N, Dhinojwala A, Jacobs TDB, Pastewka L. Why soft contacts are stickier when breaking than when making them. SCIENCE ADVANCES 2024; 10:eadl1277. [PMID: 38446897 PMCID: PMC10917342 DOI: 10.1126/sciadv.adl1277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 01/30/2024] [Indexed: 03/08/2024]
Abstract
Soft solids are sticky. They attract each other and spontaneously form a large area of contact. Their force of attraction is higher when separating than when forming contact, a phenomenon known as adhesion hysteresis. The common explanation for this hysteresis is viscoelastic energy dissipation or contact aging. Here, we use experiments and simulations to show that it emerges even for perfectly elastic solids. Pinning by surface roughness triggers the stick-slip motion of the contact line, dissipating energy. We derive a simple and general parameter-free equation that quantitatively describes contact formation in the presence of roughness. Our results highlight the crucial role of surface roughness and present a fundamental shift in our understanding of soft adhesion.
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Affiliation(s)
- Antoine Sanner
- Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
- Cluster of Excellence livMatS, Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
- Institute for Building Materials, ETH Zurich, Zurich 8093, Switzerland
| | - Nityanshu Kumar
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA
- Science & Technology Division, Corning Incorporated, Corning, NY 14831, USA
| | - Ali Dhinojwala
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA
| | - Tevis D. B. Jacobs
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, 3700 O’Hara Street, Pittsburgh, PA 15261, USA
| | - Lars Pastewka
- Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
- Cluster of Excellence livMatS, Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
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4
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Müller C, Müser MH. How short-range adhesion slows down crack closure and contact formation. J Chem Phys 2023; 159:234705. [PMID: 38112508 DOI: 10.1063/5.0174379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Accepted: 11/21/2023] [Indexed: 12/21/2023] Open
Abstract
While viscoelastic, adhesive contact rupture of simple indenters is well studied, contact formation has received much less attention. Here, we present simulations of the formation of contact between various power law indenters and an adhesive, viscoelastic foundation. For all investigated indenters, we find that the macroscopic relaxation time τ scales approximately with 1/ρ1.8, where ρ is the range of adhesion. The prolongation of contact formation with Tabor parameter is rationalized by the increased dissipation that short-range adhesion causes on a moving crack.
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Affiliation(s)
- C Müller
- INM-Leibniz Institute for New Materials, 66123 Saarbrücken, Germany
| | - M H Müser
- Department of Materials Science and Engineering, Saarland University, 66123 Saarbrücken, Germany
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5
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Zhu J, Yang C, Liu Q. Experimental characterization of elastocapillary and osmocapillary effects on multi-scale gel surface topography. SOFT MATTER 2023; 19:8698-8705. [PMID: 37938918 DOI: 10.1039/d3sm01147j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Surface topography significantly affects various surface properties of polymer gels. Unlike conventional materials where surface topography is largely a geometric property, the surface topography of a polymer gel is governed by the competition between capillary, elastic, and osmotic effects, which leads to complex stimuli-responsive effects. Elastocapillary deformation and osmocapillary phase separation are two phenomena that are known to flatten gel surface topography. Here we experimentally quantify how osmocapillary phase separation affects gel surface topography by fabricating ionogels with multi-scale topography and characterizing the swelling-dependent surface flattening. Our observation confirms the vital role of the osmocapillary length in governing the surface behavior of swollen ionogels. This study provides the first quantitative experimental verification of the osmocapillary phase separation and shows the insufficiency of the previous studies based on elastocapillary deformation alone.
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Affiliation(s)
- Jie Zhu
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15213, USA.
| | - Canhui Yang
- Shenzhen Key Laboratory of Soft Mechanics & Smart Manufacturing, Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen, Guangdong 518055, P. R. China
| | - Qihan Liu
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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6
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Afferrante L, Violano G, Carbone G. Exploring the dynamics of viscoelastic adhesion in rough line contacts. Sci Rep 2023; 13:15060. [PMID: 37699918 PMCID: PMC10497551 DOI: 10.1038/s41598-023-39932-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 08/02/2023] [Indexed: 09/14/2023] Open
Abstract
Modeling the adhesion of viscoelastic rough surfaces is a recent challenge in contact mechanics. Existing models have primarily focused on simple systems with smooth topography or single roughness scale due to the co-action of roughness and viscoelasticity leading to elastic instabilities and rate-dependent behavior, resulting in complex adhesion dynamics. In this study, we propose a numerical model based on a finite element methodology to investigate the adhesion between a randomly rough profile and a viscoelastic half-plane. Approach-retraction simulations are performed under controlled displacement conditions of the rough indenter. The results demonstrate that viscous effects dampen the roughness-induced instabilities in both the approach and retraction phases. Interestingly, even when viscous effects are negligible, the pull-off stress, i.e., the maximum tensile stress required to detach the surfaces, is found to depend on the stiffness modulus and maximum load reached during the approach. Furthermore, when unloading is performed from a relaxed state of the viscoelastic half-plane, both adhesion hysteresis and pull-off stress are monotonic increasing functions of the speed. Conversely, when retraction begins from an unrelaxed state of the material, the maximum pull-off stress and hysteretic loss are obtained at intermediate velocities.
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Affiliation(s)
- Luciano Afferrante
- Department of Mechanics, Mathematics and Management, Polytechnic University of Bari, Via E. Orabona, 4, 70125, Bari, Italy
| | - Guido Violano
- Department of Materials Science and Engineering, Saarland University, Campus, Geb. C6.3, 66123, Saarbrücken, Germany.
| | - Giuseppe Carbone
- Department of Mechanics, Mathematics and Management, Polytechnic University of Bari, Via E. Orabona, 4, 70125, Bari, Italy
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7
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Farain K, Bonn D. Predicting frictional aging from bulk relaxation measurements. Nat Commun 2023; 14:3606. [PMID: 37330517 DOI: 10.1038/s41467-023-39350-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 06/08/2023] [Indexed: 06/19/2023] Open
Abstract
The coefficient of static friction between solids normally increases with the time they have remained in static contact before the measurement. This phenomenon, known as frictional aging, is at the origin of the difference between static and dynamic friction coefficients but has remained difficult to understand. It is usually attributed to a slow expansion of the area of atomic contact as the interface changes under pressure. This is however challenging to quantify as surfaces have roughness at all length scales. In addition, friction is not always proportional to the contact area. Here we show that the normalized stress relaxation of the surface asperities during frictional contact with a hard substrate is the same as that of the bulk material, regardless of the asperities' size or degree of compression. This result enables us to predict the frictional aging of rough interfaces based on the bulk material properties of two typical polymers: polypropylene and polytetrafluoroethylene.
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Affiliation(s)
- Kasra Farain
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, Netherlands
| | - Daniel Bonn
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, Netherlands.
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8
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Understanding How Cells Probe the World: A Preliminary Step towards Modeling Cell Behavior? Int J Mol Sci 2023; 24:ijms24032266. [PMID: 36768586 PMCID: PMC9916635 DOI: 10.3390/ijms24032266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/16/2023] [Accepted: 01/20/2023] [Indexed: 01/26/2023] Open
Abstract
Cell biologists have long aimed at quantitatively modeling cell function. Recently, the outstanding progress of high-throughput measurement methods and data processing tools has made this a realistic goal. The aim of this paper is twofold: First, to suggest that, while much progress has been done in modeling cell states and transitions, current accounts of environmental cues driving these transitions remain insufficient. There is a need to provide an integrated view of the biochemical, topographical and mechanical information processed by cells to take decisions. It might be rewarding in the near future to try to connect cell environmental cues to physiologically relevant outcomes rather than modeling relationships between these cues and internal signaling networks. The second aim of this paper is to review exogenous signals that are sensed by living cells and significantly influence fate decisions. Indeed, in addition to the composition of the surrounding medium, cells are highly sensitive to the properties of neighboring surfaces, including the spatial organization of anchored molecules and substrate mechanical and topographical properties. These properties should thus be included in models of cell behavior. It is also suggested that attempts at cell modeling could strongly benefit from two research lines: (i) trying to decipher the way cells encode the information they retrieve from environment analysis, and (ii) developing more standardized means of assessing the quality of proposed models, as was done in other research domains such as protein structure prediction.
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9
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Müser MH, Nicola L. Modeling the surface topography dependence of friction, adhesion, and contact compliance. MRS BULLETIN 2023; 47:1221-1228. [PMID: 36846502 PMCID: PMC9947065 DOI: 10.1557/s43577-022-00468-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 11/28/2022] [Indexed: 06/18/2023]
Abstract
The small-scale topography of surfaces critically affects the contact area of solids and thus the forces acting between them. Although this has long been known, only recent advances made it possible to reliably model interfacial forces and related quantities for surfaces with multiscale roughness. This article sketches both recent and traditional approaches to their mechanics, while addressing the relevance of nonlinearity and nonlocality arising in soft- and hard-matter contacts.
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Affiliation(s)
- Martin H. Müser
- Department of Materials Science and Engineering, Saarland University, Saarbrücken, Germany
| | - Lucia Nicola
- Department of Industrial Engineering, University of Padua, Padua, Italy
- Department of Materials Engineering, Delft University of Technology, Delft, The Netherlands
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10
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Park J, Lee J, Han S, Lee HR, Choi SQ. Removal Analysis of Residual Photoresist Particles Based on Surface Topography Affected by Exposure Times of Ultraviolet and Developer Solution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:16134-16143. [PMID: 36520112 DOI: 10.1021/acs.langmuir.2c02882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Particle removal from the surface of a substrate has been an issue in numerous fields for a long time. In semiconductor processes, for instance, the formation of clean surfaces by removing photoresist (PR) must be followed in order to create neat patterns. Although PR removal has been intensively investigated recently, little is known about how ultraviolet (UV) and developer solutions alter the PR resin (and in what manner) near the surface. While varying the exposure times of UV and developer solution, we investigated the topographic changes on the surfaces of PR resin films and particles. The measured surface properties were then correlated with the detachment force determined using films, and eventually with the residual PR particle removal percentages obtained in a microchannel. Using a positive PR and a base developer solution, we demonstrated that UV causes the surface of PR resin to become hydrophilic and wavy, whereas the developer solution produces a surface with a larger degree of roughness by swelling and partially dissolving the resin. Ultimately, the increased roughness decreased the effective contact area between PR resins, hence decreasing the detachment force and increasing the particle removal percentages. We anticipate that our findings will help understand residual particle issues, particularly on the removal mechanism of PR resins based on surface topography.
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Affiliation(s)
- Jinwon Park
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Jaehong Lee
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Seongsoo Han
- Mineral Processing and Metallurgy Research Center, Resources Utilization Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon 34132, Korea
| | - Hyun-Ro Lee
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Siyoung Q Choi
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
- KAIST Institute for the Nanocentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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11
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Core-shell dry adhesives for rough surfaces via electrically responsive self-growing strategy. Nat Commun 2022; 13:7659. [PMID: 36496484 PMCID: PMC9741600 DOI: 10.1038/s41467-022-35436-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 12/02/2022] [Indexed: 12/13/2022] Open
Abstract
Bioinspired dry adhesives have an extraordinary impact in the field of robotic manipulation and locomotion. However, there is a considerable difference between artificial structures and biological ones regarding surface adaptability, especially for rough surfaces. This can be attributed to their distinct structural configuration and forming mechanism. Here, we propose a core-shell adhesive structure that is obtained through a growth strategy, i.e., an electrically responsive self-growing core-shell structure. This growth strategy results in a specific mushroom-shaped structure with a rigid core and a soft shell, which exhibits excellent adhesion on typical target surfaces with roughness ranging from the nanoscale to the microscale up to dozens of micrometers. The proposed adhesion strategy extends dry adhesives from smooth surfaces to rough ones, especially for rough surfaces with roughness up to dozens or hundreds of micrometers, opening an avenue for the development of dry adhesive-based devices and systems.
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12
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Orndorf N, Garner AM, Dhinojwala A. Polar bear paw pad surface roughness and its relevance to contact mechanics on snow. J R Soc Interface 2022; 19:20220466. [PMID: 36321372 PMCID: PMC9627446 DOI: 10.1098/rsif.2022.0466] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 10/11/2022] [Indexed: 11/04/2023] Open
Abstract
Microscopic papillae on polar bear paw pads are considered adaptations for increased friction on ice/snow, yet this assertion is based on a single study of one species. The lack of comparative data from species that exploit different habitats renders the ecomorphological associations of papillae unclear. Here, we quantify the surface roughness of the paw pads of four species of bear over five orders of magnitude by calculating their surface roughness power spectral density. We find that interspecific variation in papillae base diameter can be explained by paw pad width, but that polar bear paw pads have 1.5 times taller papillae and 1.3 times more true surface area than paw pads of the American black bear and brown bear. Based on friction experiments with three-dimensional printed model surfaces and snow, we conclude that these factors increase the frictional shear stress of the polar bear paw pad on snow by a factor of 1.3-1.5 compared with the other species. Absolute frictional forces, however, are estimated to be similar among species once paw pad area is accounted for, suggesting that taller papillae may compensate for frictional losses resulting from the relatively smaller paw pads of polar bears compared with their close relatives.
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Affiliation(s)
- Nathaniel Orndorf
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA
| | - Austin M. Garner
- Integrated Bioscience Program, Department of Biology, The University of Akron, Akron, OH 44325, USA
| | - Ali Dhinojwala
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA
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13
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Gaire B, Wilson MC, Singla S, Dhinojwala A. Connection between Molecular Interactions and Mechanical Work of Adhesion. ACS Macro Lett 2022; 11:1285-1290. [DOI: 10.1021/acsmacrolett.2c00499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Babu Gaire
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Michael C. Wilson
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Saranshu Singla
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Ali Dhinojwala
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
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14
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Maksuta D, Dalvi S, Gujrati A, Pastewka L, Jacobs TDB, Dhinojwala A. Dependence of adhesive friction on surface roughness and elastic modulus. SOFT MATTER 2022; 18:5843-5849. [PMID: 35900052 DOI: 10.1039/d2sm00163b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Friction is one of the leading causes of energy loss in moving parts, and understanding how roughness affects friction is of utmost importance. From creating surfaces with high friction to prevent slip and movement, to creating surfaces with low friction to minimize energy loss, roughness plays a key role. By measuring shear stresses of crosslinked elastomers on three rough surfaces of similar surface chemistry across nearly six decades of sliding velocity, we demonstrate the dominant role of adhesive frictional dissipation. Furthermore, while it was previously known that roughness-induced oscillations affected the viscoelastic dissipation, we show that these oscillations also control the molecular detachment process and the resulting adhesive dissipation. This contrasts with typical models of friction, where only the amount of contact area and the strength of interfacial bonding govern the adhesive dissipation. Finally, we show that all the data can be collapsed onto a universal curve when the shear stress is scaled by the square root of elastic modulus and the velocity is scaled by a critical velocity at which the system exhibits macroscopic buckling instabilities. Taken together, these results suggest a design principle broadly applicable to frictional systems ranging from tires to soft robotics.
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Affiliation(s)
- Daniel Maksuta
- Department of Biology, Integrated Bioscience Program, The University of Akron, Akron, Ohio, 44325, USA
| | - Siddhesh Dalvi
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, USA.
| | - Abhijeet Gujrati
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, 15261, USA
| | - Lars Pastewka
- Department of Microsystems Engineering, University of Freiburg, 79110 Freiburg, Germany
| | - Tevis D B Jacobs
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania, 15261, USA
| | - Ali Dhinojwala
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, USA.
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15
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Ding R, Miller NC, Woeppel KM, Cui XT, Jacobs TDB. Surface Area and Local Curvature: Why Roughness Improves the Bioactivity of Neural Implants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7512-7521. [PMID: 35678760 PMCID: PMC10080668 DOI: 10.1021/acs.langmuir.2c00473] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
While roughening the surface of neural implants has been shown to significantly improve their performance, the mechanism for this improvement is not understood, preventing systematic optimization of surfaces. Specifically, prior work has shown that the cellular response to a surface can be significantly enhanced by coating the implant surface with inorganic nanoparticles and neuroadhesion protein L1, and this improvement occurs even when the surface chemistry is identical between the nanoparticle-coated and uncoated electrodes, suggesting the critical importance of surface topography. Here, we use transmission electron microscopy to characterize the topography of bare and nanoparticle-coated implants across 7 orders of magnitude in size, from the device scale to the atomic scale. The results reveal multiscale roughness, which cannot be adequately described using conventional roughness parameters. Indeed, the topography is nearly identical between the two samples at the smallest scales and also at the largest scales but vastly different in the intermediate scales, especially in the range of 5-100 nm. Using a multiscale topography analysis, we show that the coating causes a 76% increase in the available surface area for contact and an order-of-magnitude increase in local surface curvature at characteristic sizes corresponding to specific biological structures. These are correlated with a 75% increase in bound proteins on the surface and a 134% increase in neurite outgrowth. The present investigation presents a framework for analyzing the scale-dependent topography of medical device-relevant surfaces, and suggests the most critical size scales that determine the biological response to implanted materials.
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Affiliation(s)
- Ruikang Ding
- Mechanical Engineering & Materials Science, University of Pittsburgh, 3700 O'Hara St., Benedum Hall Room 636, Pittsburgh, Pennsylvania 15261, United States
| | - Nathaniel C Miller
- Mechanical Engineering & Materials Science, University of Pittsburgh, 3700 O'Hara St., Benedum Hall Room 636, Pittsburgh, Pennsylvania 15261, United States
| | - Kevin M Woeppel
- Bioengineering, University of Pittsburgh, 5057 Biomedical Science Tower 3, 3501 Fifth Ave, Pittsburgh, Pennsylvania 15260, United States
- Center for the Neural Basis of Cognition, 4400 Fifth Ave, Suite 115, Pittsburgh, Pennsylvania 15213, United States
| | - Xinyan T Cui
- Bioengineering, University of Pittsburgh, 5057 Biomedical Science Tower 3, 3501 Fifth Ave, Pittsburgh, Pennsylvania 15260, United States
- Center for the Neural Basis of Cognition, 4400 Fifth Ave, Suite 115, Pittsburgh, Pennsylvania 15213, United States
- McGowan Institute for Regenerative Medicine, Pittsburgh, Pennsylvania 15213, United States
| | - Tevis D B Jacobs
- Mechanical Engineering & Materials Science, University of Pittsburgh, 3700 O'Hara St., Benedum Hall Room 636, Pittsburgh, Pennsylvania 15261, United States
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16
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Ma J, Zheng Z, Hoque MJ, Li L, Rabbi KF, Ho JY, Braun PV, Wang P, Miljkovic N. A Lipid-Inspired Highly Adhesive Interface for Durable Superhydrophobicity in Wet Environments and Stable Jumping Droplet Condensation. ACS NANO 2022; 16:4251-4262. [PMID: 35275638 DOI: 10.1021/acsnano.1c10250] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Creating thin (<100 nm) hydrophobic coatings that are durable in wet conditions remains challenging. Although the dropwise condensation of steam on thin hydrophobic coatings can enhance condensation heat transfer by 1000%, these coatings easily delaminate. Designing interfaces with high adhesion while maintaining a nanoscale coating thickness is key to overcoming this challenge. In nature, cell membranes face this same challenge where nanometer-thick lipid bilayers achieve high adhesion in wet environments to maintain integrity. Nature ensures this adhesion by forming a lipid interface having two nonpolar surfaces, demonstrating high physicochemical resistance to biofluids attempting to open the interface. Here, developing an artificial lipid-like interface that utilizes fluorine-carbon molecular chains can achieve durable nanometric hydrophobic coatings. The application of our approach to create a superhydrophobic material shows high stability during jumping-droplet-enhanced condensation as quantified from a continual one-year steam condensation experiment. The jumping-droplet condensation enhanced condensation heat transfer coefficient up to 400% on tube samples when compared to filmwise condensation on bare copper. Our bioinspired materials design principle can be followed to develop many durable hydrophobic surfaces using alternate substrate-coating pairs, providing stable hydrophobicity or superhydrophobicity to a plethora of applications.
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Affiliation(s)
- Jingcheng Ma
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Zhuoyuan Zheng
- Department of Industrial and Enterprise Systems Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Muhammad Jahidul Hoque
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Longnan Li
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Kazi Fazle Rabbi
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Jin Yao Ho
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Paul V Braun
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
- Department of Materials Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
| | - Pingfeng Wang
- Department of Industrial and Enterprise Systems Engineering, University of Illinois, Urbana, Illinois 61801, United States
| | - Nenad Miljkovic
- Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, United States
- Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801, United States
- International Institute for Carbon Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
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17
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Ledesma-Alonso R, Raphael E, Restagno F, Poulard C. Effect of the density of pillar-patterned substrates on contact mechanics: Transition from top to mixed contact with a detailed pressure-field description. Phys Rev E 2021; 104:055007. [PMID: 34942743 DOI: 10.1103/physreve.104.055007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/25/2021] [Indexed: 11/07/2022]
Abstract
Different contact regimes between a spherical lens and a periodically patterned substrate are observed, when they are pressed against each other. Top contact occurs when only the highest substrate sections touch the lens, whereas mixed contact implies that both the highest and the lowest substrate sections come into contact with the lens. In this paper, we study how the pattern density of the substrate, along with its physical properties and those of the lens, determine the transition from top contact to mixed contact. Experiments and numerical simulations had been performed, as complementary approaches to obtain data, and a theoretical analysis has been developed to gain insight on the effect of the physical parameters on the contact transition. As a result, a phase diagram is presented, in terms of the load and the contact radius, that combines the observations of the three approaches (experimental, numerical, and theoretical), unveiling the boundaries of three contact regimes: (1) deterministic-driven contact, (2) top contact, and (3) mixed contact.
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Affiliation(s)
- R Ledesma-Alonso
- Departamento de Ingeniería Industrial y Mecánica, Escuela de Ingeniería, Universidad de las Américas Puebla, San Andrés Cholula, Puebla, C.P. 72810, México
| | - E Raphael
- Laboratoire de Physico-Chimie Théorique, UMR CNRS/ESPCI Gulliver 7083, 75005 Paris, France
| | - F Restagno
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay Cedex, France
| | - C Poulard
- Université Paris-Saclay, CNRS, Laboratoire de Physique des Solides, 91405 Orsay Cedex, France
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18
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Affiliation(s)
- Guido Raos
- Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, Via L. Mancinelli 7, I-20131 Milano, Italy
| | - Bruno Zappone
- Consiglio Nazionale delle Ricerche - Istituto di Nanotecnologia (CNR-Nanotec), Via P. Bucci, 33/C, 87036 Rende (CS), Italy
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19
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Narayanan A, Dhinojwala A, Joy A. Design principles for creating synthetic underwater adhesives. Chem Soc Rev 2021; 50:13321-13345. [PMID: 34751690 DOI: 10.1039/d1cs00316j] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Water and adhesives have a conflicting relationship as demonstrated by the failure of most man-made adhesives in underwater environments. However, living creatures routinely adhere to substrates underwater. For example, sandcastle worms create protective reefs underwater by secreting a cocktail of protein glue that binds mineral particles together, and mussels attach themselves to rocks near tide-swept sea shores using byssal threads formed from their extracellular secretions. Over the past few decades, the physicochemical examination of biological underwater adhesives has begun to decipher the mysteries behind underwater adhesion. These naturally occurring adhesives have inspired the creation of several synthetic materials that can stick underwater - a task that was once thought to be "impossible". This review provides a comprehensive overview of the progress in the science of underwater adhesion over the past few decades. In this review, we introduce the basic thermodynamics processes and kinetic parameters involved in adhesion. Second, we describe the challenges brought by water when adhering underwater. Third, we explore the adhesive mechanisms showcased by mussels and sandcastle worms to overcome the challenges brought by water. We then present a detailed review of synthetic underwater adhesives that have been reported to date. Finally, we discuss some potential applications of underwater adhesives and the current challenges in the field by using a tandem analysis of the reported chemical structures and their adhesive strength. This review is aimed to inspire and facilitate the design of novel synthetic underwater adhesives, that will, in turn expand our understanding of the physical and chemical parameters that influence underwater adhesion.
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Affiliation(s)
- Amal Narayanan
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA.
| | - Ali Dhinojwala
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA.
| | - Abraham Joy
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA.
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20
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Interfacial Dissipative Phenomena in Tribomechanical Systems. LUBRICANTS 2021. [DOI: 10.3390/lubricants9100104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The last decade has experienced a tremendous development of several technologies that are likely to shape our future [...]
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21
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van Engers CD, Lamberty ZD, McGuiggan PM, Frechette J. Template-Stripped Ultra-Smooth Aluminum Films (0.2 nm RMS) for the Surface Forces Apparatus. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:6556-6565. [PMID: 34009999 DOI: 10.1021/acs.langmuir.1c00899] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We present a method for the fabrication of ultra-smooth (0.2 nm RMS), aluminum substrates through template stripping (TS). The method relies on the use of mica as a template in combination with thermal evaporation of Al at high (>10 nm/s) rates under vacuum (≤1 × 10-7 Torr). As a reactive metal, Al is usually not considered a viable option for TS off oxide templates. However, under these conditions, the adhesion between the Al film and mica is poor, enabling the removal of the template under water without any mica residue. We verify the absence of mica using atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. We establish the suitability of these films for surface forces measurements. Multiple-bean interferometry in transmission yields high quality fringes allowing for the measurement of force-distance curves. The adhesion the films to mica is significantly higher than the adhesion of thermally evaporated Al (0.9 nm RMS). Preliminary results suggest that the TS-Al surface displays a higher corrosion resistance. The fabrication method will enable important experiments on this widely used material.
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Affiliation(s)
- Christian D van Engers
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Zachary D Lamberty
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Patricia M McGuiggan
- Department of Materials Science and Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Joelle Frechette
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
- Hopkins Extreme Materials Institute, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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22
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Gaire B, Singla S, Dhinojwala A. Screening of hydrogen bonding interactions by a single layer graphene. NANOSCALE 2021; 13:8098-8106. [PMID: 33956918 DOI: 10.1039/d0nr08843a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A single layer of graphene when transferred to a solid substrate has the ability to screen or transmit interactions from the underlying substrate, which has direct consequences in applications of this 2D material to flexible electronics and sensors. Previous reports using a multitude of techniques present contradictory views on graphene's ability to screen or transmit van der Waals (vdW) and polar interactions. In the present study, we use interface-sensitive spectroscopy to demonstrate that a single layer graphene is opaque to hydrogen bonding interactions (a subset of acid-base interactions), answering a question that has remained unresolved for a decade. Similar frequency shifts of sapphire hydroxyl (OH) peak for graphene-coated sapphire in contact with air and polydimethylsiloxane (PDMS) demonstrate the insensitivity of sapphire OH to PDMS. The screening ability of graphene is also evident in the smaller magnitude of this frequency shift for graphene-coated sapphire in comparison to that for bare sapphire. The screening of acid-base interactions by a single layer graphene results in the significant reduction of adhesion hysteresis for PDMS lens on graphene-coated substrates (sapphire and silicon wafer, SiO2/Si) than bare substrates. Our results have implications in the use of PDMS stamps to transfer graphene to other substrates eliminating the need for a wet-transfer process.
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Affiliation(s)
- Babu Gaire
- School of Polymer Science and Polymer Engineering, University of Akron, Akron, OH 44325, USA.
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23
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On the Effect of a Rate-Dependent Work of Adhesion in the Detachment of a Dimpled Surface. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11073107] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Patterned surfaces have proven to be a valuable design to enhance adhesion, increasing hysteresis and the detachment stress at pull-off. To obtain high adhesive performance, soft materials are commonly, used, which easily conform to the countersurface, such as soft polymers and elastomers. Such materials are viscoelastic; i.e., they show rate-dependent properties. Here, the detachment of two half spaces is studied, one being flat and the other having a dimple in the limit of short range adhesion and a power law rate-dependent work of adhesion, as observed by several authors. Literature results have suggested that the dimpled surface would show pressure-sensitive adhesion, showing two possible adhered states, one weak, in partial contact, and one strong when full contact is achieved. By accounting for a power law rate-dependent work of adhesion, the “weak state” may be much stronger than it was in the purely elastic case, and hence the interface may be much more tough to separate. We study the pull-off detachment stress of the dimpled surface, showing that it weakly depends on the preload, but it is strongly affected by the dimensionless unloading rate. Finally, possible implications of the presented results in the detachment of soft materials from rough substrates are discussed.
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24
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Abstract
When an elastomer approaches or retracts from an adhesive indenter, the elastomer’s surface can suddenly become unstable and reshape itself quasi-discontinuously, e.g., when small-scale asperities jump into or snap out of contact. Such dynamics lead to a hysteresis between approach and retraction. In this study, we quantify numerically and analytically the ensuing unavoidable energy loss for rigid indenters with flat, Hertzian and randomly rough profiles. The range of adhesion turns out to be central, in particular during the rarely modeled approach to contact. For example, negligible traction on approach but quite noticeable adhesion for nominal plane contacts hinges on the use of short-range adhesion. Central attention is paid to the design of cohesive-zone models for the efficient simulation of dynamical processes. Our study includes a Griffith’s type analysis for the energy lost during fracture and regeneration of a flat interface. It reveals that the leading-order corrections of the energy loss are due to the finite-range adhesion scale at best, with the third root of the linear mesh size, while leading-order errors in the pull-off force disappear linearly.
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25
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Abstract
It is known that in the presence of surface roughness, adhesion can lead to distinct paths of loading and unloading for the area–load and penetration–load relationships, thus causing hysteretic loss. Here, we investigate the effects that the surface roughness parameters have on such adhesive hysteresis loss. We focus on the frictionless normal contact between soft elastic bodies and, for this reason, we model adhesion according to Johnson, Kendall, and Roberts (JKR) theory. Hysteretic energy loss is found to increase linearly with the true area of contact, while the detachment force is negligibly influenced by the maximum applied load reached at the end of the loading phase. Moreover, for the micrometric roughness amplitude hrms considered in the present work, adhesion hysteresis is found to be affected by the shorter wavelengths of roughness. Specifically, hysteresis losses decrease with increasing fractal dimension and cut-off frequency of the roughness spectrum. However, we stress that a different behavior could occur in other ranges of roughness amplitude.
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26
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Hui CY, Liu Z, Bain N, Jagota A, Dufresne ER, Style RW, Kiyama R, Gong JP. How surface stress transforms surface profiles and adhesion of rough elastic bodies. Proc Math Phys Eng Sci 2020; 476:20200477. [PMID: 33362416 DOI: 10.1098/rspa.2020.0477] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 10/06/2020] [Indexed: 01/07/2023] Open
Abstract
The surface of soft solids carries a surface stress that tends to flatten surface profiles. For example, surface features on a soft solid, fabricated by moulding against a stiff-patterned substrate, tend to flatten upon removal from the mould. In this work, we derive a transfer function in an explicit form that, given any initial surface profile, shows how to compute the shape of the corresponding flattened profile. We provide analytical results for several applications including flattening of one-dimensional and two-dimensional periodic structures, qualitative changes to the surface roughness spectrum, and how that strongly influences adhesion.
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Affiliation(s)
- Chung-Yuen Hui
- Field of Theoretical and Applied Mechanics, Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA.,Global Station for Soft Matter, GI-CoRE, Hokkaido University, Sapporo, Japan
| | - Zezhou Liu
- Field of Theoretical and Applied Mechanics, Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Nicolas Bain
- Laboratory of Soft and Living Materials, Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Anand Jagota
- Departments of Bioengineering and of Chemical and Biomolecular Engineering, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA
| | - Eric R Dufresne
- Laboratory of Soft and Living Materials, Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Robert W Style
- Laboratory of Soft and Living Materials, Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Ryuji Kiyama
- Graduate School of Life Science, Hokkaido University, Sapporo 001-0021, Japan
| | - Jian Ping Gong
- Global Station for Soft Matter, GI-CoRE, Hokkaido University, Sapporo, Japan.,Faculty of Advanced Life Science, Hokkaido University, Sapporo 001-0021, Japan.,WPI-ICReDD, Hokkaido University, Sapporo 001-0021, Japan
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27
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Tiwari A, Wang J, Persson BNJ. Adhesion paradox: Why adhesion is usually not observed for macroscopic solids. Phys Rev E 2020; 102:042803. [PMID: 33212630 DOI: 10.1103/physreve.102.042803] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 09/30/2020] [Indexed: 11/07/2022]
Abstract
The adhesion paradox refers to the observation that for most solid objects no adhesion can be detected when they are separated from a state of molecular contact. The adhesion paradox results from surface roughness, and we present experimental and theoretical results that show that adhesion in most cases is "killed" by the longest-wavelength roughness. In addition, adhesion experiments between a human finger and a clean glass plate were carried out, and for a dry finger no macroscopic adhesion occurred. We suggest that the observed decrease in the contact area with increasing shear force results from nonadhesive finger-glass contact mechanics, involving large deformations of complex layered material.
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Affiliation(s)
- A Tiwari
- PGI-1, FZ Jülich, Germany, Jülich 52428, European Union
| | - J Wang
- PGI-1, FZ Jülich, Germany, Jülich 52428, European Union.,College of Science, Zhongyuan University of Technology, Zhengzhou 450007, China
| | - B N J Persson
- PGI-1, FZ Jülich, Germany, Jülich 52428, European Union
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28
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Physicochemical and Mechanical Performance of Freestanding Boron-Doped Diamond Nanosheets Coated with C:H:N:O Plasma Polymer. MATERIALS 2020; 13:ma13081861. [PMID: 32326555 PMCID: PMC7215835 DOI: 10.3390/ma13081861] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Revised: 04/09/2020] [Accepted: 04/13/2020] [Indexed: 01/22/2023]
Abstract
The physicochemical and mechanical properties of thin and freestanding heavy boron-doped diamond (BDD) nanosheets coated with a thin C:H:N:O plasma polymer were studied. First, diamond nanosheets were grown and doped with boron on a Ta substrate using the microwave plasma-enhanced chemical vapor deposition technique (MPECVD). Next, the BDD/Ta samples were covered with nylon 6.6 to improve their stability in harsh environments and flexibility during elastic deformations. Plasma polymer films with a thickness of the 500–1000 nm were obtained by magnetron sputtering of a bulk target of nylon 6.6. Hydrophilic nitrogen-rich C:H:N:O was prepared by the sputtering of nylon 6.6. C:H:N:O as a film with high surface energy improves adhesion in ambient conditions. The nylon–diamond interface was perfectly formed, and hence, the adhesion behavior could be attributed to the dissipation of viscoelastic energy originating from irreversible energy loss in soft polymer structure. Diamond surface heterogeneities have been shown to pin the contact edge, indicating that the retraction process causes instantaneous fluctuations on the surface in specified microscale regions. The observed Raman bands at 390, 275, and 220 cm−1 were weak; therefore, the obtained films exhibited a low level of nylon 6 polymerization and short-distance arrangement, indicating crystal symmetry and interchain interactions. The mechanical properties of the nylon-on-diamond were determined by a nanoindentation test in multiload mode. Increasing the maximum load during the nanoindentation test resulted in a decreased hardness of the fabricated structure. The integration of freestanding diamond nanosheets will make it possible to design flexible chemical multielectrode sensors.
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29
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Dalvi S, Gujrati A, Khanal SR, Pastewka L, Dhinojwala A, Jacobs TDB. Linking energy loss in soft adhesion to surface roughness. Proc Natl Acad Sci U S A 2019; 116:25484-25490. [PMID: 31772024 PMCID: PMC6925979 DOI: 10.1073/pnas.1913126116] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A mechanistic understanding of adhesion in soft materials is critical in the fields of transportation (tires, gaskets, and seals), biomaterials, microcontact printing, and soft robotics. Measurements have long demonstrated that the apparent work of adhesion coming into contact is consistently lower than the intrinsic work of adhesion for the materials, and that there is adhesion hysteresis during separation, commonly explained by viscoelastic dissipation. Still lacking is a quantitative experimentally validated link between adhesion and measured topography. Here, we used in situ measurements of contact size to investigate the adhesion behavior of soft elastic polydimethylsiloxane hemispheres (modulus ranging from 0.7 to 10 MPa) on 4 different polycrystalline diamond substrates with topography characterized across 8 orders of magnitude, including down to the angstrom scale. The results show that the reduction in apparent work of adhesion is equal to the energy required to achieve conformal contact. Further, the energy loss during contact and removal is equal to the product of the intrinsic work of adhesion and the true contact area. These findings provide a simple mechanism to quantitatively link the widely observed adhesion hysteresis to roughness rather than viscoelastic dissipation.
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Affiliation(s)
- Siddhesh Dalvi
- Department of Polymer Science, The University of Akron, Akron, OH 44325
| | - Abhijeet Gujrati
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261
| | - Subarna R Khanal
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261
| | - Lars Pastewka
- Department of Microsystems Engineering, University of Freiburg, 79110 Freiburg, Germany
| | - Ali Dhinojwala
- Department of Polymer Science, The University of Akron, Akron, OH 44325;
| | - Tevis D B Jacobs
- Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261;
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