Dynamic self-assembly of motile bacteria in liquid crystals

Mushenheim, Peter C.; Trivedi, Rishi R.; Tuson, Hannah H.; Weibel, Douglas B.; Abbott, Nicholas L.

doi:10.1039/c3sm52423j

Cited by 116 publications

(191 citation statements)

References 37 publications

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“…The coating induces homeotropic anchoring of the aggregates on the cylinder surfaces through noncovalent interactions (53) thereby enabling the experimental studies of LCLCs confined in curved geometries with homeotropic alignment. Other than for their biocompatibility (54,55), LCLCs are known for their very small twist modulus compared with splay and bend moduli; this property renders LCLCs susceptible to spontaneous chiral symmetry breaking (56,57).…”

Section: Significancementioning

confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

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

109

103

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We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymercoated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects.mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1-11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10-14) relevant for applications ranging from chemical sensors (15, 16) to photonics (17-19). To date, considerable effort has been expended to control handedness in materials (for example, by chiral separation of racemic mixtures or chiral amplification of small enantiomeric imbalances) (1,8,(20)(21)(22). Recently and in a different vein, identification and elucidation of pathways by which achiral building blocks spontaneously organize to create chiral structures have become an area of active study. Examples of these pathways include packing with multiple competing length scales (8-10, 23, 24), reconfiguration through mechanical instabilities of periodic structures (20,25,26), and helix formation of flexible cylinders through inter-and intracylinder interactions (27,28). In addition, the system of a broken chiral symmetry often consists of domains of opposite handedness with defects separating the domains.Liquid crystals (LCs) are soft materials composed ...

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Section: Significancementioning

confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

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

109

103

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“…43,44 Additionally, the patterns and order induced in theses LCLC films could be transferred to suspended colloids, suspended nanotubes and bacterial systems to create novel metamaterial films. [21][22][23][24][25] …”

Section: -9 |mentioning

confidence: 99%

“…As a result, their mesophases differ significantly from thermotropic and amphiphilic lyotropic liquid crystals. Patterned films of LCLCs have a wide variety of emerging applications distinct from other types of liquid crystals, including inexpensive polarizing films, [12][13][14] holographic displays, 15,16 organic electronics and solar cells, 17,18 biosensors, 19,20 , aqueous colloidal, nanotube and bacterial assembly, [21][22][23][24][25] and precursors to structured graphene-based materials. 26,27 LCLCs also offer useful attributes for fundamental investigation of the effects of elasticity on self-assembly behavior, since their elastic properties can be tuned via control of mesogen concentration, 28 depletants and ions.…”

Section: Introductionmentioning

confidence: 99%

Elasticity-dependent self-assembly of micro-templated chromonic liquid crystal films

et al. 2014

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We explore micropatterned director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on squarelattice cylindrical-micropost substrates. The structures are manipulated by modulating the LCLC mesophases and their elastic properties via concentration through drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films, dried from nematics, form two distinct director and defect configurations: a diagonally aligned director pattern with local squares of defects, and an off-diagonal configuration with zig-zag defects. The formation of these states appears to be tied to the relative splay and bend free energy costs of the initial nematic films. The observed nematic and columnar configurations are understood numerically using a Landau-de Gennes free energy model. Among other attributes, the work provide first examples of quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC films in general, and it demonstrates alignment and configuration switching of typically difficult-to-align LCLC films via bulk elastic properties.

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“…[32][33][34][35][36]. The material exhibits unique optical and mechanical properties, including guidance of bacteria along the nematic director, visualization of nanometer-thick bacterial flagella [32], transport of cargo along bacterial trajectories [33], and dynamic self-assembly of bacterial clusters [35].…”

Section: Introductionmentioning

confidence: 99%

Topological Defects in a Living Nematic Ensnare Swimming Bacteria

et al. 2017

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Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement with the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of þ1=2 topological defects and depletion of bacteria in the cores of −1=2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.

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Dynamic self-assembly of motile bacteria in liquid crystals

Cited by 116 publications

References 37 publications

Chiral structures from achiral liquid crystals in cylindrical capillaries

Chiral structures from achiral liquid crystals in cylindrical capillaries

Elasticity-dependent self-assembly of micro-templated chromonic liquid crystal films

Topological Defects in a Living Nematic Ensnare Swimming Bacteria

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