1
|
Yoshikawa C, Nguyen DA, Nakaji-Hirabayashi T, Takigawa I, Mamitsuka H. Graph Network-Based Simulation of Multicellular Dynamics Driven by Concentrated Polymer Brush-Modified Cellulose Nanofibers. ACS Biomater Sci Eng 2024; 10:2165-2176. [PMID: 38546298 DOI: 10.1021/acsbiomaterials.3c01888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Manipulating the three-dimensional (3D) structures of cells is important for facilitating to repair or regenerate tissues. A self-assembly system of cells with cellulose nanofibers (CNFs) and concentrated polymer brushes (CPBs) has been developed to fabricate various cell 3D structures. To further generate tissues at an implantable level, it is necessary to carry out a large number of experiments using different cell culture conditions and material properties; however this is practically intractable. To address this issue, we present a graph-neural network-based simulator (GNS) that can be trained by using assembly process images to predict the assembly status of future time steps. A total of 24 (25 steps) time-series images were recorded (four repeats for each of six different conditions), and each image was transformed into a graph by regarding the cells as nodes and the connecting neighboring cells as edges. Using the obtained data, the performances of the GNS were examined under three scenarios (i.e., changing a pair of the training and testing data) to verify the possibility of using the GNS as a predictor for further time steps. It was confirmed that the GNS could reasonably reproduce the assembly process, even under the toughest scenario, in which the experimental conditions differed between the training and testing data. Practically, this means that the GNS trained by the first 24 h images could predict the cell types obtained 3 weeks later. This result could reduce the number of experiments required to find the optimal conditions for generating cells with desired 3D structures. Ultimately, our approach could accelerate progress in regenerative medicine.
Collapse
Affiliation(s)
- Chiaki Yoshikawa
- Research Center for Functional Materials, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0047, Japan
| | - Duc Anh Nguyen
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tadashi Nakaji-Hirabayashi
- Graduate School of Science and Engineering, University of Toyama, Toyama, Toyama 930-8555, Japan
- Graduate School of Innovative Life Science, University of Toyama, Toyama, Toyama 930-0194, Japan
| | - Ichigaku Takigawa
- Center for Innovative Research and Education in Data Science (CIREDS), Institute for Liberal Arts and Sciences, Kyoto University, Kyoto, Kyoto 606-8315, Japan
| | - Hiroshi Mamitsuka
- Bioinformatics Center, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| |
Collapse
|
2
|
Takahashi Y, Mizukami M, Tsujii Y, Kurihara K. Surface Forces Characterization of Concentrated PMMA Brush Layers under Applied Load and Shear. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:325-334. [PMID: 38128474 DOI: 10.1021/acs.langmuir.3c02606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Concentrated polymer brushes (CPBs) are known to exhibit excellent lubrication properties. However, the frictional behaviors of CPBs vary, depending on their preparation and operating conditions. In order to understand such complicated properties, it is necessary to determine their structures and correlate them with their properties, during shear motion. In this study, we employed surface forces and resonance shear measurement (RSM) as well as refractive index measurement using fringes of equal chromatic order (FECO) for studying the structure of the CPBs of poly(methyl methacrylate) (PMMA) in toluene. The obtained elastic (ks) and viscous (bs) parameters based on the RSM for the PMMA-PMMA were higher than those obtained for PMMA-silica over the entire distance range. With the increasing shear amplitude on the PMMA-PMMA under an applied load, the bs value first increased and then decreased while the ks value monotonically decreased. These behaviors were consistent with those of the thicker CPBs reported in a previous paper (Soft Matter, 2019). Thus, the dynamics of the CPBs under the applied load and shear were not dependent on the thickness of the polymer brushes in this case. The density distribution of the swollen PMMA brushes along the distance in the thickness direction of the brush layer was estimated by using the measured refractive index values, showing that the fraction of the PMMA brushes in the outer region from the surface (20% in the thickness) was ca. 10%. This lower density region near the surface of the swollen CPBs enabled them to interpenetrate with each other. Changes in the refractive index value under shear were observed, indicating that the interpenetrated PMMA chains were pulled out with increasing shear amplitude. These results demonstrated that broader applications of CPBs are possible by regulating the friction between them under different operating conditions, even for usually lubricious CPBs.
Collapse
Affiliation(s)
- Yutaka Takahashi
- New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Masashi Mizukami
- New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, Miyagi 980-8577, Japan
| | - Yoshinobu Tsujii
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kazue Kurihara
- New Industry Creation Hatchery Center (NICHe), Tohoku University, Sendai, Miyagi 980-8577, Japan
| |
Collapse
|
3
|
Okubo H, Kagiwata D, Nakano K, Tsujii Y. Layered Structure and Wear Mechanism of Concentrated Polymer Brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:18458-18465. [PMID: 38053276 PMCID: PMC10734216 DOI: 10.1021/acs.langmuir.3c02751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/10/2023] [Accepted: 11/18/2023] [Indexed: 12/07/2023]
Abstract
Concentrated polymer brushes (CPBs), which are significantly denser and thicker than conventional semidilute polymer brushes, have received increasing attention in the field of tribology because of their superlow friction properties. However, despite numerous studies aimed at enhancing CPBs for mechanical applications, the relationship between the specific layered structure and lubrication mechanisms of CPBs is still not completely understood. In this study, to reveal the relationship, simultaneous time-resolved measurements of the interfacial gap, static mechanical response, and dynamic mechanical response of the CPB at the contact interface were conducted using optical interference and precise force measuring methods. Two types of tests (i.e., the "indentation" and "sliding" tests) were alternately performed on a glass substrate coated with the CPB against a steel ball immersed in an ionic liquid. The indentation tests measuring the time-resolved interfacial gap and changes in static and dynamic mechanical responses quantitatively confirmed the presence of dilute, middle, and concentrated layers in the CPB. In the sliding tests, the wear of the CPB was detected by observing a decrease in the interfacial gap at the contact interface. Moreover, the thickness of the dilute layer remained constant with sliding, whereas the thicknesses of the other layers decreased, indicating that the dilute layer was continuously formed due to sliding. Therefore, CPB wear occurs randomly at the friction interface alongside the formation of a dilute layer with low density and stiffness on the surface.
Collapse
Affiliation(s)
- Hikaru Okubo
- Yokohama
National University, Yokohama 240-8501, Japan
| | | | - Ken Nakano
- Yokohama
National University, Yokohama 240-8501, Japan
| | - Yoshinobu Tsujii
- Institute
for Chemical Research, Kyoto University, Uji 611-0011, Japan
| |
Collapse
|
4
|
Beheshti A, Huang Y, Blakey I, Stokes JR. Macroscale superlubricity induced by film-forming polymer brush-grafted colloidal additives. J Colloid Interface Sci 2023; 634:703-714. [PMID: 36563427 DOI: 10.1016/j.jcis.2022.12.079] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 11/22/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022]
Abstract
HYPOTHESIS Modifying surfaces with concentrated polymer brushes (CPBs) is an effective way to reduce friction of tribo-pairs lubricated with liquids. We investigate the hypothesis that colloids grafted with CPBs (hybrid colloids) can deposit onto tribo-substrates by varying the solvent quality with respect to the polymer, in order to obtain ultra-low coefficients of friction (CoFs), so-called superlubricity. EXPERIMENTS Hybrid colloids are synthesized and characterized, and a dynamic light scattering compares their swellings in aqueous solutions of glycerol or polyethylene glycol. A mini-traction machine with viscoelastic tribo-pairs is used for lubrication experiments. Adsorption of colloids and film structures are tested using a quartz crystal microbalance and an atomic force microscope. FINDINGS The solvent controls whether hybrid colloids spontaneously adsorb to the substrate under quiescent conditions or require contact forces to enable (tribo-)deposition. In both cases, the friction in the boundary-mixed lubrication regimes is lower upon increasing the degree of swelling of CPBs and upon increasing coverage of deposited colloids. The greatest lubrication enhancement and surface coverage occur for the spontaneously adsorbed colloids, with ultra-low CoFs of order 10-3 over a large range of speeds. The results demonstrate the potential for hybrid colloids to be used as solvent dispersible "friction modifier additives".
Collapse
Affiliation(s)
- Amir Beheshti
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Yun Huang
- Australian National Fabrication Facility Queensland Node (ANFF-Q), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Idriss Blakey
- Centre for Advanced Imaging, Centre for Innovation in Biomedical Imaging Technology, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Jason R Stokes
- School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
| |
Collapse
|
5
|
Yoshikawa C, Takagi R, Nakaji-Hirabayashi T, Ochi T, Kawamura Y, Thissen H. Marine Antifouling Coatings Based on Durable Bottlebrush Polymers. ACS APPLIED MATERIALS & INTERFACES 2022; 14:32497-32509. [PMID: 35816694 DOI: 10.1021/acsami.2c06647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We report a next-generation, biocide-free, and durable marine antifouling coating technology. To achieve this, we combined two different polymers previously developed by us. First, we synthesized well-defined 2-hydroxypropyl acrylamide (HPA) based bottlebrush polymers with concentrated polymer brush (CPB) structures, which exhibit excellent bioinertness, and second, we synthesized photoreactive copolymers of 2-hydroxypropyl acrylamide (HPA) and N-benzophenone acrylamide (BPA), which can be cross-linked by exposure to sunlight for 30 min. Simply mixing the bottlebrush polymers with the photoreactive copolymers and applying these as a coating provided a scalable method for achieving effective antifouling properties in one step on a broad range of polymer substrate materials. The resistance of bottlebrushes against acid and base hydrolysis was demonstrated in accelerated degradation experiments at 80 °C, and the coating thickness was found to be stable after 3 months of incubation in sea water. Optimized coatings prevented cypris larva attachment for up to 9 days and prevented the settling of marine organisms in the sea for up to 73 days. Due to the ease of application, long-term durability, and effective antifouling performance, our bottlebrush coating technology is expected to be exploited in biocide-free marine paints.
Collapse
Affiliation(s)
- Chiaki Yoshikawa
- Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-2-1 Tsukuba, Ibaraki 305-0047, Japan
| | - Ryoma Takagi
- Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-2-1 Tsukuba, Ibaraki 305-0047, Japan
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, Toyama 930-8555, Japan
| | - Tadashi Nakaji-Hirabayashi
- Research Center for Functional Materials, National Institute for Materials Science (NIMS), 1-2-1 Tsukuba, Ibaraki 305-0047, Japan
- Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, Toyama 930-8555, Japan
- Graduate School of Innovative Life Science, University of Toyama, 2630 Sugitani, Toyama, Toyama 930-0194, Japan
| | - Toshiro Ochi
- Kansai Paint Co., Ltd., 4-17-1 Hiratsuka, Kanagawa 254-8562, Japan
| | - Yasushi Kawamura
- Kansai Paint Co., Ltd., 4-17-1 Hiratsuka, Kanagawa 254-8562, Japan
| | - Helmut Thissen
- CSIRO Manufacturing, Research Way, Clayton, Victoria 3168, Australia
| |
Collapse
|
6
|
Vlădescu SC, Tadokoro C, Miyazaki M, Reddyhoff T, Nagamine T, Nakano K, Sasaki S, Tsujii Y. Exploiting the Synergy between Concentrated Polymer Brushes and Laser Surface Texturing to Achieve Durable Superlubricity. ACS APPLIED MATERIALS & INTERFACES 2022; 14:15818-15829. [PMID: 35333041 PMCID: PMC9007417 DOI: 10.1021/acsami.2c00725] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Friction continues to account for the bulk of energy losses in mechanical systems, with an estimated 23% of the world's total energy consumption used to overcome friction. Concentrated polymer brushes (CPBs) have recently attracted significant scientific and industrial attention, given their ability to achieve superlubricity (i.e., coefficients of friction below 0.01); however, understanding the mechanistic interactions underlying their wear performance has been largely overlooked. Herein, we employ a custom-built optical test apparatus to investigate the inter-dependencies between CPBs and laser-produced surface texture (LST), assessing for the first time the friction, film thickness, and wear behavior in situ and simultaneously. Recent developments in picosecond laser etching allowed us to graft CPBs atop the finest laser-etched matrix of micron-sized dimples reported in literature to date. At low sliding speeds, combined CPB-LST reduces the coefficient of friction to 0.0006, while increasing the CPB durability by up to 34% through a lateral support mechanism offered by the textured micro-features. Furthermore, the imaging results shed light on CPB failure mechanisms. Both these mechanisms of lateral support and failure propagation impact the wear resistance of CPBs and are important in the development of CPBs for future applications (e.g., in low-speed bearings functioning under controlled abrasive wear conditions).
Collapse
Affiliation(s)
- Sorin-Cristian Vlădescu
- Tribology
Group, Department of Mechanical Engineering, Imperial College London, South Kensington, Exhibition Road, London SW7 2AZ, U.K.
- Faculty
of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan
| | - Chiharu Tadokoro
- Department
of Mechanical Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan
| | - Mayu Miyazaki
- Faculty
of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan
| | - Tom Reddyhoff
- Tribology
Group, Department of Mechanical Engineering, Imperial College London, South Kensington, Exhibition Road, London SW7 2AZ, U.K.
| | - Takuo Nagamine
- Department
of Mechanical Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama 338-8570, Japan
| | - Ken Nakano
- Faculty
of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan
| | - Shinya Sasaki
- Department
of Mechanical Engineering, Tokyo University
of Science, Tokyo 125-8585, Japan
| | - Yoshinobu Tsujii
- Institute
for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| |
Collapse
|
7
|
Liu Z, Ootani Y, Uehara S, Xu J, Wang Y, Miyazaki N, Higuchi Y, Ozawa N, Kubo M. Coarse-grained Molecular Dynamics Simulation of the Wear Mechanism of Cyclic Polymer Brushes. CHEM LETT 2020. [DOI: 10.1246/cl.200323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Zhongmin Liu
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Yusuke Ootani
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Shuichi Uehara
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Jingxiang Xu
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
- College of Engineering Science and Technology, Shanghai Ocena University, Shanghai 201306, P. R. China
| | - Yang Wang
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
- Department of Mechanical Systems Engineering, Graduate School of Engineering, Tohoku University, 6-6-01 Aramaki-aza-aoba, Aoba-ku, Sendai, Miyagi 980-8579, Japan
| | - Narumasa Miyazaki
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Yuji Higuchi
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Nobuki Ozawa
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Momoji Kubo
- Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| |
Collapse
|
8
|
Hsu SY, Ohno K, Sakakibara K, Tsujii Y. Convenient Synthesis of Very-Thick Concentrated Polymer Brushes by Atom Transfer Radical Polymerization in an Ionic Liquid. Macromolecules 2020. [DOI: 10.1021/acs.macromol.0c00161] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shu-Yao Hsu
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Kohji Ohno
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Keita Sakakibara
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| | - Yoshinobu Tsujii
- Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
| |
Collapse
|
9
|
Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film. COATINGS 2020. [DOI: 10.3390/coatings10020153] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ionic liquids have unique characteristics, which render them ideal candidates as new base oils or additives. In particular, there are great expectations from the combination of diamond-like carbon and cyano-based ionic liquids. Lubricating properties of cyano-based ionic liquids have been studied on specific tetrahedral amorphous carbon (ta-C) films. After lubrication, ta-C film/ta-C film contact interface exhibits exceedingly low friction. Therefore, it is necessary to understand this low friction phenomenon. The current study evaluated the lubricating mechanism of cyano-based ionic liquids against ta-C films. 1-Butyl-3-methylimidazolium dicyanamide ((BMIM)(DCN)) and 1-butyl-3-methylimidazolium tricyanomethane ((BMIM)(TCC)) were used as lubricants, with the latter exhibiting low friction coefficient of 0.03. Steel cylinders and disks with ta-C films were used as test specimens. Raman spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and thermogravimetric analysis (TGA) helped us understand the mechanism of low friction induced by (BMIM)(TCC). Graphitization of the ta-C film at high temperatures might have caused the reduction in friction between the films. Similarly, anion adsorption on the worn surface at high temperatures also led to reduced friction. However, the TGA result showed a different trend than that of the sliding test. Our results indicate that the cyano-based ionic liquids underwent tribo-decomposition at low temperatures. Further, a minimum temperature was required for the adsorption of anions onto the sliding surface.
Collapse
|
10
|
Hsu SY, Kayama Y, Ohno K, Sakakibara K, Fukuda T, Tsujii Y. Controlled Synthesis of Concentrated Polymer Brushes with Ultralarge Thickness by Surface-Initiated Atom Transfer Radical Polymerization under High Pressure. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b02072] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Shu-Yao Hsu
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yuzo Kayama
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kohji Ohno
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Keita Sakakibara
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Takeshi Fukuda
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yoshinobu Tsujii
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| |
Collapse
|
11
|
Pidhatika B, Nalam PC. Investigation of design parameters in generating antifouling and lubricating surfaces using hydrophilic polymer brushes. J Appl Polym Sci 2019. [DOI: 10.1002/app.47659] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bidhari Pidhatika
- Laboratory for Surface Science and Technology, Department of MaterialsETH Zürich Vladimir‐Prelog‐Weg 1‐5/10, 8093, Zurich Switzerland
| | - Prathima C. Nalam
- Laboratory for Surface Science and Technology, Department of MaterialsETH Zürich Vladimir‐Prelog‐Weg 1‐5/10, 8093, Zurich Switzerland
| |
Collapse
|
12
|
Low Friction, Lubricity, and Durability of Polymer Brush Coatings, Characterized Using the Relaxation Tribometer Technique †. LUBRICANTS 2018. [DOI: 10.3390/lubricants6020052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
13
|
Stoyanov P, Chromik RR. Scaling Effects on Materials Tribology: From Macro to Micro Scale. MATERIALS (BASEL, SWITZERLAND) 2017; 10:E550. [PMID: 28772909 PMCID: PMC5459061 DOI: 10.3390/ma10050550] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/25/2017] [Accepted: 05/02/2017] [Indexed: 11/16/2022]
Abstract
The tribological study of materials inherently involves the interaction of surface asperities at the micro to nanoscopic length scales. This is the case for large scale engineering applications with sliding contacts, where the real area of contact is made up of small contacting asperities that make up only a fraction of the apparent area of contact. This is why researchers have sought to create idealized experiments of single asperity contacts in the field of nanotribology. At the same time, small scale engineering structures known as micro- and nano-electromechanical systems (MEMS and NEMS) have been developed, where the apparent area of contact approaches the length scale of the asperities, meaning the real area of contact for these devices may be only a few asperities. This is essentially the field of microtribology, where the contact size and/or forces involved have pushed the nature of the interaction between two surfaces towards the regime where the scale of the interaction approaches that of the natural length scale of the features on the surface. This paper provides a review of microtribology with the purpose to understand how tribological processes are different at the smaller length scales compared to macrotribology. Studies of the interfacial phenomena at the macroscopic length scales (e.g., using in situ tribometry) will be discussed and correlated with new findings and methodologies at the micro-length scale.
Collapse
Affiliation(s)
- Pantcho Stoyanov
- Department of Mining and Materials Engineering, Aluminum Research Centre-REGAL, McGill University, Montreal, QC H3A 0C5, Canada.
| | - Richard R Chromik
- Department of Mining and Materials Engineering, Aluminum Research Centre-REGAL, McGill University, Montreal, QC H3A 0C5, Canada.
| |
Collapse
|
14
|
Singh MK, Ilg P, Espinosa-Marzal RM, Spencer ND, Kröger M. Influence of Chain Stiffness, Grafting Density and Normal Load on the Tribological and Structural Behavior of Polymer Brushes: A Nonequilibrium-Molecular-Dynamics Study. Polymers (Basel) 2016; 8:E254. [PMID: 30974530 PMCID: PMC6431904 DOI: 10.3390/polym8070254] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 06/24/2016] [Accepted: 07/01/2016] [Indexed: 12/16/2022] Open
Abstract
We have performed coarse-grained molecular-dynamics simulations on both flexible and semiflexible multi-bead-spring model polymer brushes in the presence of explicit solvent particles, to explore their tribological and structural behaviors. The effect of stiffness and tethering density on equilibrium-brush height is seen to be well reproduced within a Flory-type theory. After discussing the equilibrium behavior of the model brushes, we first study the shearing behavior of flexible chains at different grafting densities covering brush and mushroom regimes. Next, we focus on the effect of chain stiffness on the tribological behavior of polymer brushes. The tribological properties are interpreted by means of the simultaneously recorded density profiles. We find that the friction coefficient decreases with increasing persistence length, both in velocity and separation-dependency studies, over the stiffness range explored in this work.
Collapse
Affiliation(s)
- Manjesh K Singh
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
| | - Patrick Ilg
- School of Mathematical and Physical Sciences, University of Reading, Reading RG6 6AX, UK.
| | - Rosa M Espinosa-Marzal
- Laboratory for Smart Interfaces in Environmental Nanotechnology, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61801, USA.
| | - Nicholas D Spencer
- Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
| | - Martin Kröger
- Polymer Physics, Department of Materials, ETH Zurich, CH⁻8093 Zurich, Switzerland.
| |
Collapse
|
15
|
Shimizu Y, Yoshikawa C, Suzuki J, Qiu J, van den Bosch E. Concentrated polymer brushes do not induce the expression of inflammatory and angiogeneic genes in human umbilical vein endothelial cells. Biotechnol Lett 2015; 38:403-8. [PMID: 26608604 DOI: 10.1007/s10529-015-2005-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 11/17/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVE When polymer brushes are applied as the inner coating for artificial blood vessels, they may induce unwanted responses in vascular endothelial cells continuously exposed to the polymer surface. Accordingly, we have examined the in vitro effect of non-biofouling concentrated polymer brushes (CPBs) on pro-inflammatory and angiogenic responses of human umbilical vein endothelial cells (HUVECs). RESULTS Micro-patterned CPBs were prepared on silicon wafers using biocompatible polymers, poly(poly(ethylene glycol)methyl ether methacrylate) (PPEGMA) and poly(2-hydroxyethyl methacrylate) (PHEMA). HUVECs were cultured on PPEGMA-CPBs and PHEMA-CPBs with different channel widths (20, 50, and 80 µm) and analyzed for mRNA expression of the pro-inflammatory cytokines IL-6 and IL-8 and angiogeneic vascular endothelial growth factor (VEGF). Irrespective of channel width, PHEMA-CPBs reduced the expression of all target genes, whereas PPEGMA-CPBs reduced VEGF and did not affect IL-6 and IL-8 levels. CONCLUSION Micro-patterned CPBs, irrespective of chemical structure or adhesion area, do not induce the expression of important pro-inflammatory and angiogenic mediators in endothelial cells.
Collapse
Affiliation(s)
- Yoshihisa Shimizu
- World Premier International Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0047, Japan
| | - Chiaki Yoshikawa
- World Premier International Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0047, Japan.
| | - Junji Suzuki
- World Premier International Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, 305-0047, Japan
| | - Jun Qiu
- DSM Ahead, P.O. Box 18, 6160 MD, Geleen, The Netherlands
| | | |
Collapse
|
16
|
Singh MK, Ilg P, Espinosa-Marzal RM, Kröger M, Spencer ND. Polymer Brushes under Shear: Molecular Dynamics Simulations Compared to Experiments. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:4798-4805. [PMID: 25830715 DOI: 10.1021/acs.langmuir.5b00641] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Surfaces coated with polymer brushes in a good solvent are known to exhibit excellent tribological properties. We have performed coarse-grained equilibrium and nonequilibrium molecular dynamics (MD) simulations to investigate dextran polymer brushes in an aqueous environment in molecular detail. In a first step, we determined simulation parameters and units by matching experimental results for a single dextran chain. Analyzing this model when applied to a multichain system, density profiles of end-tethered polymer brushes obtained from equilibrium MD simulations compare very well with expectations based on self-consistent field theory. Simulation results were further validated against and correlated with available experimental results. The simulated compression curves (normal force as a function of surface separation) compare successfully with results obtained with a surface forces apparatus. Shear stress (friction) obtained via nonequilibrium MD is contrasted with nanoscale friction studies employing colloidal-probe lateral force microscopy. We find good agreement in the hydrodynamic regime and explain the observed leveling-off of the friction forces in the boundary regime by means of an effective polymer-wall attraction.
Collapse
Affiliation(s)
| | - Patrick Ilg
- §School of Mathematical and Physical Sciences, University of Reading, Reading RG6 6AX, United Kingdom
| | - Rosa M Espinosa-Marzal
- ∥Laboratory for Smart Interfaces in Environmental Nanotechnology, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, United States
| | | | | |
Collapse
|
17
|
Nomura A, Goto A, Ohno K, Kayahara E, Yamago S, Tsujii Y. Controlled synthesis of hydrophilic concentrated polymer brushes and their friction/lubrication properties in aqueous solutions. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/pola.25005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
18
|
Arita T, Yoshimura T, Adschiri T. Size exclusion chromatography of quantum dots by utilizing nanoparticle repelling surface of concentrated polymer brush. NANOSCALE 2010; 2:1467-1473. [PMID: 20820736 DOI: 10.1039/c0nr00157k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We have found that the concentrated poly(methyl methacrylate) (PMMA) brush showed the very good nanoparticles (NPs) repellency in its good solvent, e.g. tetrahydrofuran (THF). Whereas the oil- and hydro-phobic (fluorinated), hydrophobic and hydrophilic surfaces adsorbed a lot of NPs. The repellency of NPs did not depend on the surface nature of the NPs. Preparing absorption free columns for size exclusion chromatography (SEC) may enable us to separate quantum dots (QDs) and NPs according to their size. By installing the concentrated PMMA brush into silica monolith columns, we tried to achieve SEC of QDs and NPs. The concentrated PMMA brush immobilized silica monolith columns were prepared by surface initiated atom transfer polymerization of MMA. As a result, we have succeeded in separating QDs according to their size. This SEC system may be advantageous because it can be used in good solvents of the brush regardless of the stability of the surface modifier layer on the NPs.
Collapse
Affiliation(s)
- Toshihiko Arita
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aobaku, Sendai 980-8577, Japan.
| | | | | |
Collapse
|