Planar anchoring strength and pitch measurements in achiral and chiral chromonic liquid crystals using 90-degree twist cells

McGinn, Christine K.; Laderman, Laura; Zimmermann, Natalie; Kitzerow, Heinz‐S.; Collings, Peter J.

doi:10.1103/physreve.88.062513

Cited by 36 publications

(41 citation statements)

References 24 publications

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“…degenerate in the local plane of the interface. Even if the surface in contact with an LCLC is unidirectionally treated (say, rubbed), the azimuthal anchoring energy is very weak, only about W∼0.3×10 −6 J m −2 [48].…”

Section: W Bactmentioning

confidence: 99%

Dynamic states of swimming bacteria in a nematic liquid crystal cell with homeotropic alignment

et al. 2017

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Flagellated bacteria such as Escherichia coli and Bacillus subtilis exhibit effective mechanisms for swimming in fluids and exploring the surrounding environment. In isotropic fluids such as water, the bacteria change swimming direction through the run-and-tumble process. Lyotropic chromonic liquid crystals (LCLCs) have been introduced recently as an anisotropic environment in which the direction of preferred orientation, the director, guides the bacterial trajectories. In this work, we describe the behavior of bacteria B. subtilis in a homeotropic LCLC geometry, in which the director is perpendicular to the bounding plates of a shallow cell. We demonstrate that the bacteria are capable of overcoming the stabilizing elastic forces of the LCLC and swim perpendicularly to the imposed director (and parallel to the bounding plates). The effect is explained by a finite surface anchoring of the director at the bacterial body; the role of surface anchoring is analyzed by numerical simulations of a rod realigning in an otherwise uniform director field. Shear flows produced by a swimming bacterium cause director distortions around its body, as evidenced both by experiments and numerical simulations. These distortions contribute to a repulsive force that keeps the swimming bacterium at a distance of a few micrometers away from the bounding plates. The homeotropic alignment of the director imposes two different scenarios of bacterial tumbling: one with an 180°r eversal of the horizontal velocity and the other with the realignment of the bacterium by two consecutive 90°turns. In the second case, the angle between the bacterial body and the imposed director changes from 90°to 0°and then back to 90°; the new direction of swimming does not correlate with the previous swimming direction. with a relatively flat rigid polyaromatic core and polar groups at the periphery [11][12][13]. In water, these molecules aggregate face-to-face in order to minimize the areas of unfavorable contact with water. Unlike their surfactantbased micellar and thermotropic counterparts, the LCLCs are not toxic to biological organisms [14].Recent experiments demonstrate that the prevailing direction of swimming is parallel to the directorn, i.e. to the average direction of LCLC orientation ( º -n n, = |ˆ| n 1) [7,8]. The orientational order of the LCLC environment can be controlled by temperature, the concentration of liquid crystal organic molecules, external electromagnetic fields and by surface alignment of the director [9,11,12]. The dispersion of swimming bacteria in LCLC, also called a living liquid crystal [8], offers new opportunities to control the dynamic behavior of the bacteria.The studies of swimming bacteria in LCLCs have been performed mostly for sandwich-type cells, in which the LCLC is confined between two glass plates, with the director being uniformly aligned along a certain direction in the plane of the cell (planar alignment). It has been shown that rod-like flagellated bacteria prefer to swim along the director [7,8,15,16]. It is ass...

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Section: W Bactmentioning

confidence: 99%

Dynamic states of swimming bacteria in a nematic liquid crystal cell with homeotropic alignment

et al. 2017

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“…To achieve this goal, we form the micropillar arrays on glass surfaces that are first rubbed with a fine abrasive pad (3M Trizact Foam Disc P3000). This rubbing creates nano-sized grooves in the bottom glass surface which, in turn, induce a weak, oriented planar alignment on the overlying chromonic liquid crystal 28,41 .…”

Section: Nematic Configurationsmentioning

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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“…These techniques achieve anisotropic molecular densities and orientations through controlling operation conditions of 3D‐printing processes, which contribute to the macroscopic shape‐changing behaviors of the resultant structures. Examples of the guided molecular self‐assembly techniques include tuning cross‐linking density of polymerization and aligning liquid crystal, etc.…”

Section: Bioinspired Shape‐changing Structures By 3d Printingmentioning

confidence: 99%

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

et al. 2018

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Nature has developed high-performance materials and structures over millions of years of evolution and provides valuable sources of inspiration for the design of next-generation structural materials, given the variety of excellent mechanical, hydrodynamic, optical, and electrical properties. Biomimicry, by learning from nature's concepts and design principles, is driving a paradigm shift in modern materials science and technology. However, the complicated structural architectures in nature far exceed the capability of traditional design and fabrication technologies, which hinders the progress of biomimetic study and its usage in engineering systems. Additive manufacturing (three-dimensional (3D) printing) has created new opportunities for manipulating and mimicking the intrinsically multiscale, multimaterial, and multifunctional structures in nature. Here, an overview of recent developments in 3D printing of biomimetic reinforced mechanics, shape changing, and hydrodynamic structures, as well as optical and electrical devices is provided. The inspirations are from various creatures such as nacre, lobster claw, pine cone, flowers, octopus, butterfly wing, fly eye, etc., and various 3D-printing technologies are discussed. Future opportunities for the development of biomimetic 3D-printing technology to fabricate next-generation functional materials and structures in mechanical, electrical, optical, and biomedical engineering are also outlined.

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Planar anchoring strength and pitch measurements in achiral and chiral chromonic liquid crystals using 90-degree twist cells

Cited by 36 publications

References 24 publications

Dynamic states of swimming bacteria in a nematic liquid crystal cell with homeotropic alignment

Dynamic states of swimming bacteria in a nematic liquid crystal cell with homeotropic alignment

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

Recent Progress in Biomimetic Additive Manufacturing Technology: From Materials to Functional Structures

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