Particle trapped at the isotropic-nematic liquid crystal interface: Elastocapillary phenomena and drag forces

Loudet, J.-C. and Choudhury, A. and Qiu, M. and et al, . (2022) Particle trapped at the isotropic-nematic liquid crystal interface: Elastocapillary phenomena and drag forces. Physical Review E, 105 (4). pp. 1-15. ISSN 2470-0045

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We present numerical simulations of a particle trapped at the isotropic-nematic liquid crystal (Iso-N) interface. We use our recent model, based on a phase-field approach [see Qiu, Phys. Rev. E 103, 022706 (2021)10.1103/PhysRevE.103.022706], to couple the capillary forces acting on the interface with the elastic stresses in the nematic phase along with topological defects. A range of floating configurations are first investigated as a function of the contact angle and various anchoring conditions at the fluid interface. The results show that the response of the system is driven by the existence of an anchoring conflict at the contact line. Substantial particle displacements and/or interfacial deformations may occur in this case even for moderate anchoring strengths. These findings highlight the coupling between elastic and capillary forces. In a second part, we compute drag forces exerted on a particle that moves along the Iso-N interface for several contact angles and a moderate Ericksen number. Because of the coupling between the velocity and order parameter fields, topological defects are swept downstream of the particle by the flow and sometimes escape from the particle or merge with the interface. We also find linear force-velocity laws, with drag forces at the Iso-N interface being slightly greater than their isotropic counterparts due to director distortions. We discuss these results in light of past studies on the behavior of particles being dragged in the bulk of a liquid crystal matrix. © 2022 American Physical Society.

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Additional Information: This work was financially supported by the EU Marie-Curie fellowship CoPEC under Grant No. 794837–H2020-MSCA-IF-2017 and by the NSERC Discovery Grant No. 2019-04162. J.-C.L. is also indebted to the University of Bordeaux for further financial support thanks to the IdEx program titled Développement des carrières—Volet personnel de recherche. M.Q. acknowledges support from the UBC Four-year Doctoral Fellowship. A.C. was supported by an overseas visiting doctoral fellowship from SERB, Department of Science & Technology, Government of India. We acknowledge CMC Microsystems for software licensing. The IT staff of the Mathematics department of the University of British Columbia is also gratefully acknowledged for their valuable help and support.
Uncontrolled Keywords: A-particles; Anchorings; Capillary force; Drag forces; Isotropics; Liquid crystal interface; Model-based OPC; Particle trapped; Phase-field approaches; Topological defect
Subjects: Physics > Mechanical and aerospace
Others > Biological sciences
Chemical Engineering
Divisions: Department of Mathematics
Department of Mechanical & Aerospace Engineering
Depositing User: . LibTrainee 2021
Date Deposited: 13 Jul 2022 10:45
Last Modified: 13 Jul 2022 10:45
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