Elastic Torque and the Levitation of Metal Wires by a Nematic Liquid Crystal

Lapointe, Clayton; Hultgren, A.; Silevitch, D. M.; Felton, Edward J.; Reich, Daniel H.; Leheny, Robert L.

doi:10.1126/science.1092608

Cited by 118 publications

(122 citation statements)

References 23 publications

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“…However, the gravitational force is balanced by elastic forces that repel colloids from bounding plates with strong planar boundary conditions (13,38,39). The elastic repulsive force between a dipolar colloid (Fig.…”

Section: Resultsmentioning

confidence: 99%

Large-area optoelastic manipulation of colloidal particles in liquid crystals using photoresponsive molecular surface monolayers

Martinez

Mireles

Smalyukh

2011

Proc. Natl. Acad. Sci. U.S.A.

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Noncontact optical trapping and manipulation of micrometer-and nanometer-sized particles are typically achieved by use of forces and torques exerted by tightly focused high-intensity laser beams. Although they were instrumental for many scientific breakthroughs, these approaches find few technological applications mainly because of the small-area manipulation capabilities, the need for using high laser powers, limited application to anisotropic fluids and low-refractive-index particles, as well as complexity of implementation. To overcome these limitations, recent research efforts have been directed toward extending the scope of noncontact optical control through the use of optically-guided electrokinetic forces, vortex laser beams, plasmonics, and optofluidics. Here we demonstrate manipulation of colloidal particles and self-assembled structures in nematic liquid crystals by means of single-molecule-thick, light-controlled surface monolayers. Using polarized light of intensity from 1,000 to 100,000 times smaller than that in conventional optical tweezers, we rotate, translate, localize, and assemble spherical and complex-shaped particles of various sizes and compositions. By controlling boundary conditions through the monolayer, we manipulate the liquid crystal director field and the landscape of ensuing elastic forces exerted on colloids by the host medium. This permits the centimeter-scale, massively parallel manipulation of particles and complex colloidal structures that can be dynamically controlled by changing illumination or assembled into stationary stable configurations dictated by the "memorized" optoelastic potential landscape due to the last illumination pattern. We characterize the strength of optically guided elastic forces and discuss the potential uses of this noncontact manipulation in fabrication of novel optically-and electrically-tunable composites from liquid crystals and colloids.optical manipulation | photoresponsive surface monolayers | self-assembly R econfigurable self-assembly of micrometer-and nanometersized particles of various shapes and chemical compositions is of great interest from the standpoints of both fundamental science and practical applications (1-14). The use of anisotropic liquid crystal (LC) fluids as host media for such colloidal selfassembly is currently perhaps one of the most promising approaches (2-14). It not only allows one to engender anisotropic long-range interaction forces and achieve oriented self-assembly guided by the long-range orientational order of the LC host (2), but also enables control of the medium-mediated interparticle forces by means of varying temperature, applying external fields, and utilizing the response of LC alignment to the presence of various chemical substances (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Properties of such tunable self-assembled LC-based composite micro-and nanostructured materials can be further engineered by controlling positions and orientations of constituent particles of desired material compositions, shapes, and s...

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Section: Resultsmentioning

confidence: 99%

Large-area optoelastic manipulation of colloidal particles in liquid crystals using photoresponsive molecular surface monolayers

Martinez

Mireles

Smalyukh

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…The magnetic fields required to manipulate these ferromagnetic wires are typically very small, ∼ 5 Gauss [21], much less than that required to align the liquid crystal * Electronic address: csmith8@uwo.ca † Electronic address: cdennist@uwo.ca…”

Section: Introductionmentioning

confidence: 99%

Elastic response of a nematic liquid crystal to an immersed nanowire

Denniston

2007

Journal of Applied Physics

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We study the immersion of a ferromagnetic nanowire within a nematic liquid crystal using a lattice Boltzmann algorithm to solve the full three-dimensional equations of hydrodynamics. We present an algorithm for including a moving boundary, to simulate a nanowire, in a lattice Boltzmann simulation. The nematic imposes a torque on a wire that increases linearly with the angle between the wire and the equilibrium direction of the director field. By rotation of these nanowires, one can determine the elastic constants of the nematic.

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“…This orientation occurs robustly for films of h ≈ 25 μm. This elastic alignment is enforced by a torque that rotates nanowires (24) or bullet-like particles (25) immersed within uniform LCs and can be attributed to the coupling of the topological defect created by the microcylinder and the prevailing director field. The microcylinders create a point defect at one of their flat ends ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Elastocapillary interactions on nematic films

Liu

Gharbi

Ngo

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Rod-like colloids distort fluid interfaces and interact by capillarity. We explore this interaction at the free surface of aligned nematic liquid crystal films. Naive comparison of capillary and elastic energies suggests that particle assembly would be determined solely by surface tension. Here, we demonstrate that, under certain circumstances, the capillary and elastic effects are complementary and each plays an important role. Particles assemble end-to-end, as dictated by capillarity, and align along the easy axis of the director field, as dictated by elasticity. On curved fluid interfaces, however, curvature capillary energies can overcome the elastic orientations and drive particle migration along curvature gradients. Domains of dominant interaction and their transition are investigated.curvature | anisotropic particles | interfacial assembly | topology | 2D superstructures

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Elastic Torque and the Levitation of Metal Wires by a Nematic Liquid Crystal

Cited by 118 publications

References 23 publications

Large-area optoelastic manipulation of colloidal particles in liquid crystals using photoresponsive molecular surface monolayers

Large-area optoelastic manipulation of colloidal particles in liquid crystals using photoresponsive molecular surface monolayers

Elastic response of a nematic liquid crystal to an immersed nanowire

Elastocapillary interactions on nematic films

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