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Loudet JC. Elastocapillary interaction for particles trapped at the isotropic-nematic liquid crystal interface. Phys Rev E 2024; 109:054603. [PMID: 38907388 DOI: 10.1103/physreve.109.054603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 04/11/2024] [Indexed: 06/24/2024]
Abstract
We present numerical simulations on pairwise interactions between particles trapped at an isotropic-nematic liquid crystal (Iso-N) interface. The particles are subject to elastocapillary interactions arising from interfacial deformations and elastic distortions of the nematic phase. We use a recent model based on a phase-field approach [see Qiu et al., Phys. Rev. E 103, 022706 (2021)2470-004510.1103/PhysRevE.103.022706] to take into account the coupling between elastic and capillary phenomena. The pair potential is computed in a two-dimensional geometry for a range of particle separations and two anchoring configurations. The first configuration leads to the presence of an anchoring conflict at the three-phase contact line, whereas such a conflict does not exist for the second one. In the first case, the results show that significant interfacial deformations and downward particle displacements occur, resulting in sizable attractive capillary interactions able to overcome repulsive elastic forces at intermediate separations. The pair potential exhibits an equilibrium distance since elastic repulsions prevail at short range and prevent the clustering of particles. However, in the absence of any anchoring conflict, the interfacial deformations are very small and the capillary forces have a negligible contribution to the pair potential, which is fully repulsive and overwhelmed by elastic forces. These results suggest that the self-assembly properties of particles floating at Iso-N interfaces might be controlled by tuning anchoring conflicts.
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Affiliation(s)
- J-C Loudet
- Université de Bordeaux, CNRS, Centre de Recherche Paul Pascal (UMR 5031), 33600 Pessac, France
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2
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Fu C, Lin H, Nere RN, Gharbi MA. Effect of airflow rate and drainage on the properties of 2D smectic liquid crystal foams. SOFT MATTER 2023; 19:6298-6304. [PMID: 37555339 DOI: 10.1039/d3sm00684k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
As a two-phase system, foams are widely applied in the industry and exist ubiquitously in our daily lives. For this reason, studying them and investigating the parameters that affect their properties is crucial for the development of new and improved foam-based products. In this paper, we create 2D foam using an ordered fluid, the smectic liquid crystal (LC), and discuss the experimental parameters that affect their fabrication, including temperature and confining conditions. Then, we examine the influence of the injected airflow rate and drainage on their structure, size, liquid fraction, and stability. Finally, we compare their behavior to that of low-viscosity liquid foams and discuss the difference between them. Our findings indicate that surface tension is the dominant parameter in LC foam systems. Despite the strong elasticity of LCs, surface tension plays a crucial role in determining the properties of elastic foams. These results provide valuable insights that can be applied to different industrial applications. For instance, they may find relevance in the fields of cosmetics, thermal insulation, oil recovery, and sensing, where the fabrication of foams with high-viscosity fluids is required.
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Affiliation(s)
- Changshuo Fu
- Department of Physics, University of Massachusetts, Boston, MA 02125, USA.
| | - Hongjie Lin
- Department of Physics, University of Massachusetts, Boston, MA 02125, USA.
| | - Rachel N Nere
- Department of Physics, University of Massachusetts, Boston, MA 02125, USA.
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3
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Abstract
Matter self-assembling into layers generates unique properties, including structures of stacked surfaces, directed transport, and compact area maximization that can be highly functionalized in biology and technology. Smectics represent the paradigm of such lamellar materials - they are a state between fluids and solids, characterized by both orientational and partial positional ordering in one layering direction, making them notoriously difficult to model, particularly in confining geometries. We propose a complex tensor order parameter to describe the local degree of lamellar ordering, layer displacement and orientation of the layers for simple, lamellar smectics. The theory accounts for both dislocations and disclinations, by regularizing singularities within defect cores and so remaining continuous everywhere. The ability to describe disclinations and dislocation allows this theory to simulate arrested configurations and inclusion-induced local ordering. This tensorial theory for simple smectics considerably simplifies numerics, facilitating studies on the mesoscopic structure of topologically complex systems.
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Wei WS, Jeong J, Collings PJ, Yodh AG. Focal conic flowers, dislocation rings, and undulation textures in smectic liquid crystal Janus droplets. SOFT MATTER 2022; 18:4360-4371. [PMID: 35608219 DOI: 10.1039/d1sm01623g] [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
Liquid crystalline phases of matter often exhibit visually stunning patterns or textures. Mostly, these liquid crystal (LC) configurations are uniquely determined by bulk LC elasticity, surface anchoring conditions, and confinement geometry. Here, we experimentally explore defect textures of the smectic LC phase in unique confining geometries with variable curvature. We show that a complex range of director configurations can arise from a single system, depending on sample processing procedures. Specifically, we report on LC textures in Janus drops comprised of silicone oil and 8CB in its smectic-A LC phase. The Janus droplets were made in aqueous suspension using solvent-induced phase separation. After drop creation, smectic layers form in the LC compartment, but their self-assembly is frustrated by the need to accommodate both the bowl-shaped cavity geometry and homeotropic (perpendicular) anchoring conditions at boundaries. A variety of stable and metastable smectic textures arise, including focal conic domains, dislocation rings, and undulations. We experimentally characterize their stabilities and follow their spatiotemporal evolution. Overall, a range of fabrication kinetics produce very different intermediate and final states. The observations elucidate assembly mechanisms and suggest new routes for fabrication of complex soft material structures in Janus drops and other confinement geometries.
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Affiliation(s)
- Wei-Shao Wei
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA.
- Laboratory for Research on the Structure of Matter (LRSM), University of Pennsylvania, Philadelphia, PA, USA
| | - Joonwoo Jeong
- Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan, Republic of Korea.
| | - Peter J Collings
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Physics and Astronomy, Swarthmore College, Swarthmore, PA, USA
| | - A G Yodh
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA, USA.
- Laboratory for Research on the Structure of Matter (LRSM), University of Pennsylvania, Philadelphia, PA, USA
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Xia J, MacLachlan S, Atherton TJ, Farrell PE. Structural Landscapes in Geometrically Frustrated Smectics. PHYSICAL REVIEW LETTERS 2021; 126:177801. [PMID: 33988388 DOI: 10.1103/physrevlett.126.177801] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
A phenomenological free energy model is proposed to describe the behavior of smectic liquid crystals, an intermediate phase that exhibits orientational order and layering at the molecular scale. Advantageous properties render the functional amenable to numerical simulation. The model is applied to a number of scenarios involving geometric frustration, leading to emergent structures such as focal conic domains and oily streaks and enabling detailed elucidation of the very rich energy landscapes that arise in these problems.
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Affiliation(s)
- Jingmin Xia
- Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom
| | - Scott MacLachlan
- Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7, Canada
| | - Timothy J Atherton
- Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155, USA
| | - Patrick E Farrell
- Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom
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Song X, Zhou J, Qiao C, Xu X, Zhao S, Liu H. Engulfing Behavior of Nanoparticles into Thermoresponsive Microgels: A Mesoscopic Simulation Study. J Phys Chem B 2021; 125:2994-3004. [PMID: 33720720 DOI: 10.1021/acs.jpcb.1c00817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The engulfing of nanoparticles into microgels provides a versatile platform to design nano- and microstructured materials with various shape anisotropies and multifunctional properties. Manipulating the spontaneous engulfment process remains elusive. Herein, we report a mesoscopic simulation study on the engulfing behavior of nanoparticles into thermoresponsive microgels. The effects of the multiple parameters, including binding strength, temperature, and nanoparticle size, are examined systematically. Our simulation results disclose three engulfing states at different temperatures, namely full-engulfing, half-engulfing, and surface contact. The engulfing depth is determined by the complementary balance of interfacial elastocapillarity. Specifically, the van der Waals interaction of hybrid microgel-nanoparticle offers the capillary force while the internally networked structure of microgel reinforces the elasticity repulsion. Our study, validated by relevant experimental results, provides a mechanistic understanding of the interfacial elastocapillarity for nanoparticle-microgels.
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Affiliation(s)
- Xianyu Song
- State Key Laboratory of Chemical Engineering and School of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, China.,Chongqing Key Laboratory of Water Environment Evolution and Pollution Control in Three Gorges Reservoir, Chongqing Three Gorges University, Wanzhou 404020, China
| | - Jianzhuang Zhou
- State Key Laboratory of Chemical Engineering and School of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Chongzhi Qiao
- State Key Laboratory of Chemical Engineering and School of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Xiaofei Xu
- State Key Laboratory of Chemical Engineering and School of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Shuangliang Zhao
- State Key Laboratory of Chemical Engineering and School of Chemical Engineering, East China University of Science and Technology, Shanghai, 200237, China.,Guangxi Key Laboratory of Petrochemical Resource Processing and Process Intensification Technology, Guangxi University, Nanning, 530004, China
| | - Honglai Liu
- State Key Laboratory of Chemical Engineering and School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, China
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Preusse RS, George ER, Aghvami SA, Otchy TM, Gharbi MA. Hierarchical assembly of smectic liquid crystal defects at undulated interfaces. SOFT MATTER 2020; 16:8352-8358. [PMID: 32785413 DOI: 10.1039/d0sm01112f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The assembly of topological defects in liquid crystals has drawn significant interest in the last decade due to their ability to trap colloidal objects and direct their arrangements. They have also brought about a high impact in modern technologies, in particular in optics, e.g., microlens arrays, soft lithography templates, and optically selective masks. Here we study the formation of defects in smectic A liquid crystal with hybrid texture at undulated surfaces. We investigate the role of surface topography on the organization of focal conic domains (FCDs) in smectic films. We demonstrate new methods for assembling FCDs and disclinations into hierarchical structures. When the liquid crystal is heated to the nematic phase, we observe stable defect lines forming at specific locations. These defects are created to satisfy anchoring conditions and the geometry of confinement imposed by the boundaries. Once the liquid crystal is cooled to the smectic A phase, the disclinations maintain their positions, but periodic structures of reversible FCDs facing opposite directions arise between them. We report the correlation between the size of these FCDs and their eccentricities with the morphology of the interface. This work paves the way for creating new procedures to control the assembly of functional nanomaterials into tunable assemblies that may find relevance in the field of energy technology including in optoelectronic and photonic applications.
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Affiliation(s)
- Ryan S Preusse
- Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA.
| | - Elizabeth R George
- Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA.
| | - S Ali Aghvami
- Department of Biology and Neurophotonics Center, Boston University, Boston, MA 02215, USA
| | - Timothy M Otchy
- Department of Physics, Brandeis University, Waltham, MA 02453, USA
| | - Mohamed Amine Gharbi
- Department of Physics, University of Massachusetts Boston, Boston, MA 02125, USA.
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8
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Al-DTPA microfiber assisted formwork construction technology for high-performance SiC membrane preparation. J Memb Sci 2020. [DOI: 10.1016/j.memsci.2019.117464] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Klopp C, Trittel T, Eremin A, Harth K, Stannarius R, Park CS, Maclennan JE, Clark NA. Structure and dynamics of a two-dimensional colloid of liquid droplets. SOFT MATTER 2019; 15:8156-8163. [PMID: 31595938 DOI: 10.1039/c9sm01433k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Droplet arrays in thin, freely suspended liquid-crystalline smectic A films can form two-dimensional (2D) colloids. The droplets interact repulsively, arranging locally in a more or less hexagonal arrangement with only short-range spatial and orientational correlations and local lattice cell parameters that depend on droplet size. In contrast to quasi-2D colloids described earlier, there is no 3D bulk liquid subphase that affects the hydrodynamics. Although the films are surrounded by air, the droplet dynamics are genuinely 2D, the mobility of each droplet in its six-neighbor cage being determined by the ratio of cage and droplet sizes, rather than by the droplet size as in quasi-2D colloids. These experimental observations are described well by Saffman's model of a diffusing particle in a finite 2D membrane. The experiments were performed in microgravity, on the International Space Station.
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Affiliation(s)
- Christoph Klopp
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Torsten Trittel
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Alexey Eremin
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Kirsten Harth
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Ralf Stannarius
- Institute of Physics, Otto von Guericke University, Universitätsplatz 2, D-39106 Magdeburg, Germany.
| | - Cheol S Park
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
| | - Joseph E Maclennan
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
| | - Noel A Clark
- Soft Materials Research Center, Physics Department, University of Colorado, Boulder, CO 80309, USA
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