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Capillary interaction and self-assembly of tilted magnetic ellipsoidal particles at liquid interfaces

Newton, Bethany J.; Mohammed, Rizwaan; Davies, Gary B.; Botto, Lorenzo; Buzza, D. Martin A.

Authors

Bethany J. Newton

Rizwaan Mohammed

Gary B. Davies

Lorenzo Botto

Abstract

Copyright © 2018 American Chemical Society. Magnetic ellipsoidal particles adsorbed at a liquid interface provide exciting opportunities for creating switchable functional materials, where self-assembly can be switched on and off using an external field [Davies et al., Adv. Mater., 2014, 26, 6715]. In order to gain a deeper understanding of this novel system in the presence of an external field, we study the capillary interaction and self-assembly of tilted ellipsoids using analytical theory and finite element simulations. We derive an analytical expression for the dipolar capillary interaction between tilted ellipsoids in elliptical polar coordinates, which exhibits a 1/r2 power law dependence in the far field (i.e., large particle separations r) and correctly captures the orientational dependence of the capillary interactions in the near field. Using this dipole potential and finite element simulations, we further analyze the energy landscape of particle clusters consisting of up to eight tilted ellipsoids in contact. For clusters of two particles, we find that the side-to-side configuration is stable, whereas the tip-to-tip configuration is unstable. However, for clusters of more than three particles, we find that circular loops of side-to-side particles become globally stable, whereas linear chains of side-to-side particles become metastable. Furthermore, the energy barrier for the linear-to-loop transition decreases with increasing particle number. Our results explain both thermodynamically and kinetically why tilted ellipsoids assemble side-to-side locally but have a strong tendency to form loops on larger length scales.

Journal Article Type Article
Publication Date Nov 30, 2018
Journal ACS Omega
Print ISSN 2470-1343
Electronic ISSN 2470-1343
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 3
Issue 11
Pages 14962-14972
Institution Citation Newton, B. J., Mohammed, R., Davies, G. B., Botto, L., & Buzza, D. M. A. (2018). Capillary interaction and self-assembly of tilted magnetic ellipsoidal particles at liquid interfaces. ACS Omega, 3(11), 14962-14972. doi:10.1021/acsomega.8b01818
DOI https://doi.org/10.1021/acsomega.8b01818
Publisher URL https://pubs.acs.org/doi/10.1021/acsomega.8b01818

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Copyright Statement
ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.



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