1
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Badr RGM, Hauer L, Vollmer D, Schmid F. Dynamics of Droplets Moving on Lubricated Polymer Brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:12368-12380. [PMID: 38834186 PMCID: PMC11192036 DOI: 10.1021/acs.langmuir.4c00400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 05/11/2024] [Accepted: 05/13/2024] [Indexed: 06/06/2024]
Abstract
Understanding the dynamics of drops on polymer-coated surfaces is crucial for optimizing applications such as self-cleaning materials or microfluidic devices. While the static and dynamic properties of deposited drops have been well characterized, a microscopic understanding of the underlying dynamics is missing. In particular, it is unclear how drop dynamics depends on the amount of uncross-linked chains in the brush, because experimental techniques fail to quantify those. Here we use coarse-grained simulations to study droplets moving on a lubricated polymer brush substrate under the influence of an external body force. The simulation model is based on the many body dissipative particle dynamics (MDPD) method and designed to mimic a system of water droplets on poly(dimethylsiloxane) (PDMS) brushes with chemically identical PDMS lubricant. In agreement with experiments, we find a sublinear power law dependence between the external force F and the droplet velocity v, F ∝ vα with α < 1; however, the exponents differ (α ∼ 0.6-0.7 in simulations versus α ∼ 0.25 in experiments). With increasing velocity, the droplets elongate and the receding contact angle decreases, whereas the advancing contact angle remains roughly constant. Analyzing the flow profiles inside the droplet reveals that the droplets do not slide but roll, with vanishing slip at the substrate surface. Surprisingly, adding lubricant has very little effect on the effective friction force between the droplet and the substrate, even though it has a pronounced effect on the size and structure of the wetting ridge, especially above the cloaking transition.
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Affiliation(s)
- Rodrique G. M. Badr
- Institut
für Physik, Johannes Gutenberg-Universität
Mainz, Staudingerweg 7-9, D-55099 Mainz, Germany
| | - Lukas Hauer
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Doris Vollmer
- Max
Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Friederike Schmid
- Institut
für Physik, Johannes Gutenberg-Universität
Mainz, Staudingerweg 7-9, D-55099 Mainz, Germany
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2
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Veldscholte LB, Snoeijer JH, den Otter WK, de Beer S. Pressure Anisotropy in Polymer Brushes and Its Effects on Wetting. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4401-4409. [PMID: 38358950 PMCID: PMC10905992 DOI: 10.1021/acs.langmuir.3c03727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/17/2024]
Abstract
Polymer brushes, coatings consisting of densely grafted macromolecules, experience an intrinsic lateral compressive pressure, originating from chain elasticity and excluded volume interactions. This lateral pressure complicates a proper definition of the interface and, thereby, the determination and interpretation of the interfacial tension and its relation to the wetting behavior of brushes. Here, we study the link among grafting-induced compressive lateral pressure in polymer brushes, interfacial tension, and brush wettability using coarse-grained molecular dynamics simulations. We focus on grafting densities and polymer-liquid affinities such that the polymer and liquid do not tend to mix. For these systems, a central result is that the liquid contact angle is independent of the grafting density, which implies that the grafting-induced lateral compressive pressure in the brush does not influence its wettability. Although the definition of brush interfacial tensions is complicated by the grafting-induced pressure, the difference in the interfacial tension between wet and dry brushes is perfectly well-defined. We confirm explicitly from Young's law that this difference offers an accurate description of the brush wettability. We then explore a method to isolate the grafting-induced contribution to the lateral pressure, assuming the interfacial tension is independent of grafting density. This scenario indeed allows disentanglement of interfacial and grafting effects for a broad range of parameters, except close to the mixing point. We separately discuss the latter case in light of autophobic dewetting.
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Affiliation(s)
- Lars B. Veldscholte
- Functional
Polymer Surfaces, Department of Molecules and Materials, MESA+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Jacco H. Snoeijer
- Physics
of Fluids, MESA+ Institute, University of
Twente, 7500 AE Enschede, The Netherlands
| | - Wouter K. den Otter
- Multiscale
Mechanics, Department of Fluid and Thermal Engineering, MESA+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
| | - Sissi de Beer
- Functional
Polymer Surfaces, Department of Molecules and Materials, MESA+ Institute, University of Twente, 7500 AE Enschede, The Netherlands
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3
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Ishraaq R, Akash TS, Bera A, Das S. Hydrophilic and Apolar Hydration in Densely Grafted Cationic Brushes and Counterions with Large Mobilities. J Phys Chem B 2024; 128:381-392. [PMID: 38148252 DOI: 10.1021/acs.jpcb.3c07520] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
We employ an all-atom molecular dynamics (MD) simulation framework to unravel water microstructure and ion properties for cationic [poly(2-(methacryloyloxy)ethyl) trimethylammonium chloride] (PMETAC) brushes with chloride ions as counterions. First, we identify locally separate water domains (or first hydration shells) each around {N(CH3)3}+ and the C═O functional groups of the PMETAC chain and one around the Cl- ion. These first hydration shells around the respective moieties overlap, and the extent of the overlap depends on the nature of the species triggering it. Second, despite the overlap, the water molecules in these domains demonstrate disparate properties dictated by the properties of the atoms and groups around which they are located. For example, the presence of the methyl groups makes the {N(CH3)3}+ group trigger apolar hydration as evidenced by the corresponding orientation of the dipole of the water molecules around the {N(CH3)3}+ moiety. These water molecules around the {N(CH3)3}+ group also have enhanced tetrahedrality compared to the water molecules constituting the hydration layer around the C═O group and the Cl- counterion. Our simulations also identify that there is an intervening water layer between the Cl- ion and {N(CH3)3}+ group: this layer prevents the Cl- ion from coming very close to the {N(CH3)3}+ group. As a consequence, there is a significantly large mobility of the Cl- ions inside the PMETAC brush layer. Furthermore, the C═O group of the polyelectrolyte (PE) chain, due to the partial negative charge on the oxygen atom and the specific structure of the PMETAC brush system, demonstrates strongly hydrophilic behavior and enforces a specific dipole response of water molecules analogous to that experienced by water around anionic species of high charge density. In summary, our findings confirm that PMETAC brushes undergo hydrophilic hydration at one site and apolar hydration at another site and ensure large mobility of the supported Cl- counterions.
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Affiliation(s)
- Raashiq Ishraaq
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Tanmay Sarkar Akash
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Arka Bera
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
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4
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Yanagisawa M, Watanabe C, Yoshinaga N, Fujiwara K. Cell-Size Space Regulates the Behavior of Confined Polymers: From Nano- and Micromaterials Science to Biology. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11811-11827. [PMID: 36125172 DOI: 10.1021/acs.langmuir.2c01397] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Polymer micromaterials in a liquid or gel phase covered with a surfactant membrane are widely used materials in pharmaceuticals, cosmetics, and foods. In particular, cell-sized micromaterials of biopolymer solutions covered with a lipid membrane have been studied as artificial cells to understand cells from a physicochemical perspective. The characteristics and phase transitions of polymers confined to a microscopic space often differ from those in bulk systems. The effect that causes this difference is referred to as the cell-size space effect (CSE), but the specific physicochemical factors remain unclear. This study introduces the analysis of CSE on molecular diffusion, nanostructure transition, and phase separation and presents their main factors, i.e., short- and long-range interactions with the membrane surface and small volume (finite element nature). This serves as a guide for determining the dominant factors of CSE. Furthermore, we also introduce other factors of CSE such as spatial closure and the relationships among space size, the characteristic length of periodicity, the structure size, and many others produced by biomolecular assemblies through the analysis of protein reaction-diffusion systems and biochemical reactions.
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Affiliation(s)
- Miho Yanagisawa
- Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan
| | - Chiho Watanabe
- School of Integrated Arts and Sciences, Graduate School of Integrated Sciences for Life, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima 739-8521, Japan
| | - Natsuhiko Yoshinaga
- Mathematical Science Group, WPI Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 9808577, Japan
- MathAM-OIL, National Institute of Advanced Industrial Science and Technology, Sendai 980-8577, Japan
| | - Kei Fujiwara
- Department of Biosciences & Informatics, Keio University, Yokohama 223-8522, Japan
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5
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Yanagisawa M. Cell-size space effects on phase separation of binary polymer blends. Biophys Rev 2022; 14:1093-1103. [PMID: 36345284 PMCID: PMC9636348 DOI: 10.1007/s12551-022-01001-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2022] [Indexed: 12/22/2022] Open
Abstract
Within living cells, a diverse array of biomolecules is present at high concentrations. To better understand how molecular behavior differs under such conditions (collectively described as macromolecular crowding), the crowding environment has been reproduced inside artificial cells. We have previously shown that the combination of macromolecular crowding and microscale geometries imposed by the artificial cells can alter the molecular behaviors induced by macromolecular crowding in bulk solutions. We have named the effect that makes such a difference the cell-size space effect (CSE). Here, we review the underlying biophysics of CSE for phase separation of binary polymer blends. We discuss how the cell-size space can initiate phase separation, unlike nano-sized spaces, which are known to hinder nucleation and phase separation. Additionally, we discuss how the dimensions of the artificial cell and its membrane characteristics can significantly impact phase separation dynamics and equilibrium composition. Although these findings are, of themselves, very interesting, their real significance may lie in helping to clarify the functions of the cell membrane and space size in the regulation of intracellular phase separation.
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Affiliation(s)
- Miho Yanagisawa
- Graduate School of Arts and Sciences, Komaba Institute for Science, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo, 113-0033 Japan
- Center for Complex Systems Biology, Universal Biology Institute, The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan
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6
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Badr RGM, Hauer L, Vollmer D, Schmid F. Cloaking Transition of Droplets on Lubricated Brushes. J Phys Chem B 2022; 126:7047-7058. [PMID: 36062355 DOI: 10.1021/acs.jpcb.2c04640] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study the equilibrium properties and the wetting behavior of a simple liquid on a polymer brush, with and without the presence of lubricant by multibody Dissipative Particle Dynamics simulations. The lubricant is modeled as a polymeric liquid consisting of short chains that are chemically identical with the brush polymers. We investigate the behavior of the brush in terms of the grafting density and the amount of lubricant present. Regarding the wetting behavior, we study a sessile droplet on top of the brush. The droplet consists of nonbonded particles that form a dense phase. Our model and choice of parameters result in the formation of a wetting ridge and in the cloaking of the droplet by the lubricant; i.e., the lubricant chains creep up onto the droplet and eventually cover its surface completely. Cloaking is a phenomenon that is observed experimentally and is of integral importance to the dynamics of sliding droplets. We quantify the cloaking in terms of its thickness, which increases with the amount of lubricant present. The analysis reveals a well-defined transition point where the cloaking sets in. We propose a thermodynamic theory to explain this behavior. In addition, we investigate the dependence of the contact angles on the size of the droplet and the possible effect of line tension. We quantify the variation of the contact angle with the curvature of the contact line on a lubricant free brush and find a negative value for the line tension. Finally we investigate the effect of cloaking/lubrication on the contact angles and the wetting ridge. We find that lubrication and cloaking reduce the contact angles by a couple of degrees. The effect on the wetting ridge is a reduction in the extension of the brush chains near the three phase contact line, an effect that was also observed in experiments of droplets on cross-linked gels.
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Affiliation(s)
- Rodrique G M Badr
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, D-55099 Mainz, Germany
| | - Lukas Hauer
- Max Plank Institut für Polymer Forschung Mainz, Ackermannweg 10, D-55128 Mainz, Germany
| | - Doris Vollmer
- Max Plank Institut für Polymer Forschung Mainz, Ackermannweg 10, D-55128 Mainz, Germany
| | - Friederike Schmid
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 7, D-55099 Mainz, Germany
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7
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A novel prewetting behavior of water adsorbed on solid surfaces modified with tethered chains resulting from a density functional theory. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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8
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Ritsema van Eck G, Chiappisi L, de Beer S. Fundamentals and Applications of Polymer Brushes in Air. ACS APPLIED POLYMER MATERIALS 2022; 4:3062-3087. [PMID: 35601464 PMCID: PMC9112284 DOI: 10.1021/acsapm.1c01615] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 01/03/2022] [Indexed: 05/22/2023]
Abstract
For several decades, high-density, end-tethered polymers, forming so-called polymer brushes, have inspired scientists to understand their properties and to translate them to applications. While earlier research focused on polymer brushes in liquids, it was recently recognized that these brushes can find application in air as well. In this review, we report on recent progress in unraveling fundamental concepts of brushes in air, such as their vapor-swelling and solvent partitioning. Moreover, we provide an overview of the plethora of applications in air (e.g., in sensing, separations or smart adhesives) where brushes can be key components. To conclude, we provide an outlook by identifying open questions and issues that, when solved, will pave the way for the large scale application of brushes in air.
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Affiliation(s)
- Guido
C. Ritsema van Eck
- Sustainable
Polymer Chemistry Group, Department of Molecules & Materials,
MESA+ Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Leonardo Chiappisi
- Institut
Max von Laue - Paul Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Sissi de Beer
- Sustainable
Polymer Chemistry Group, Department of Molecules & Materials,
MESA+ Institute for Nanotechnology, University
of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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9
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Li S, Shi X. 接枝高分子对纳米-生物界面粘附性能的调控研究进展. CHINESE SCIENCE BULLETIN-CHINESE 2022. [DOI: 10.1360/tb-2022-0449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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10
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Zhu Z, Tsai CY, Zhao M, Baker J, Sue HJ. PMMA Nanocomposites Based on PMMA-Grafted α-Zirconium Phosphate Nanoplatelets. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02337] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Zewen Zhu
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3003, United States
| | - Chia-Ying Tsai
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3003, United States
| | - Mingzhen Zhao
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3003, United States
| | - Joseph Baker
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3003, United States
| | - Hung-Jue Sue
- Department of Materials Science and Engineering, Texas A&M University, College Station, Texas 77843-3003, United States
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11
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Low frequency weak electric fields can induce structural changes in water. PLoS One 2021; 16:e0260967. [PMID: 34855917 PMCID: PMC8639071 DOI: 10.1371/journal.pone.0260967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 11/19/2021] [Indexed: 11/19/2022] Open
Abstract
Low frequency electric fields were exposed to various water samples using platinum electrodes mounted near the water surface. Responses were monitored using a spectro-radiometer and a contact-angle goniometer. Treatment of DI (deionized), EZ (Exclusion Zone), and bulk water with certain electromagnetic frequencies resulted in a drop of radiance persisting for at least half an hour. Compared to DI water, however, samples of EZ and bulk water showed lesser radiance drop. Contact-angle goniometric results confirmed that when treated with alternating electric fields (E = 600 ± 150 V/m, f = 7.8 and 1000 Hz), droplets of EZ and bulk water acquired different charges. The applied electric field interacted with EZ water only when electrodes were installed above the chamber, but not beneath. Further, when DI water interacted with an electric field applied from above (E = 600 ± 150 V/m, f = 75 Hz), its radiance profile became similar to that of EZ water. Putting these last two findings together, one can say that application of an electric field on DI water from above (E = 600 ± 150 V/m, f = 7.8 to 75 Hz) may induce a molecular ordering in DI water similar to that of EZ water.
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12
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Stöbener DD, Weinhart M. On the foundation of thermal "Switching": The culture substrate governs the phase transition mechanism of thermoresponsive brushes and their performance in cell sheet fabrication. Acta Biomater 2021; 136:243-253. [PMID: 34530139 DOI: 10.1016/j.actbio.2021.09.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/23/2021] [Accepted: 09/08/2021] [Indexed: 12/11/2022]
Abstract
Thermally "switchable" poly(glycidyl ether) (PGE) brushes constitute effective coatings for the temperature-triggered harvest of confluent cell sheets. Based on a simple "grafting-to" approach, such coatings can be tethered to various applied plastic culture substrate materials. Herein, we elucidate the self-assembly of PGE brushes with tunable grafting densities up to 0.12 and 0.22 chains nm-2 on polystyrene (PS) and tissue culture PS (TCPS), respectively. In terms of temperature-dependent wettability and protein adsorption, we found that brushes exhibit distinct grafting density-dependent properties which correlate with their cell sheet fabrication performance. In addition, temperature-ramped quartz-crystal microbalance with dissipation (QCM-D) measurements revealed marked substrate-specific PGE phase transitions which allowed us to deduce comprehensive switching mechanisms. Thus, we demonstrate that brushes tethered to hydrophilic TCPS (contact angle (CA) ∼ 60°) undergo a "cushioned" transition comprising a non-switchable, hydrated basal layer as well as a switchable top layer which regulates cell sheet detachment. In contrast, PGE brushes tethered to PS undergo a "grounded" transition which is substantially influenced by the dehydrating effect of the less hydrophilic PS substrate (CA ∼ 90°). These divergent phase transition mechanisms give rise to a broad scope in cell sheet fabrication performance, yielding staggered detachment times within a 30 min to 3 h range. Hence, we emphasize the importance of a detailed knowledge on the effect of applied culture substrates on the thermal switchability and phase transition characteristics of thermoresponsive brush coatings to accomplish an optimized design for functional cell culture dishes. STATEMENT OF SIGNIFICANCE: As the first comparative study of its kind, we elucidate the substrate-dependent thermal switchability of thermoresponsive brush coatings and evaluate their grafting density-dependent phase transition mechanism and its effect on cell sheet fabrication performance.
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