Chiral Liquid Crystals: Structures, Phases, Effects

Dierking, Ingo

doi:10.3390/sym6020444

Cited by 177 publications

(135 citation statements)

References 96 publications

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“…Nematic ordering is generally counteracted by orientational fluctuations. In molecular liquid crystals, these fluctuations are due to thermal rotational diffusion, which becomes large enough to disrupt the ordered phase around ∼50-250°C, depending on pressure, concentration, and chemical composition of the liquid crystal molecules and solvent fluid (50)(51)(52). In suspensions of motile bacteria, cellular alignment and collective motion (53)(54)(55)(56) are suppressed by orientational fluctuations due to variations in flagellar motor activity and cell-cell collisions that reorient cells with respect to one another (57).…”

Section: Resultsmentioning

confidence: 99%

Architectural transitions in Vibrio cholerae biofilms at single-cell resolution

Drescher

Dunkel

Nadell

et al. 2016

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

181

205

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Many bacterial species colonize surfaces and form dense 3D structures, known as biofilms, which are highly tolerant to antibiotics and constitute one of the major forms of bacterial biomass on Earth. Bacterial biofilms display remarkable changes during their development from initial attachment to maturity, yet the cellular architecture that gives rise to collective biofilm morphology during growth is largely unknown. Here, we use high-resolution optical microscopy to image all individual cells in Vibrio cholerae biofilms at different stages of development, including colonies that range in size from 2 to 4,500 cells. From these data, we extracted the precise 3D cellular arrangements, cell shapes, sizes, and global morphological features during biofilm growth on submerged glass substrates under flow. We discovered several critical transitions of the internal and external biofilm architectures that separate the major phases of V. cholerae biofilm growth. Optical imaging of biofilms with single-cell resolution provides a new window into biofilm formation that will prove invaluable to understanding the mechanics underlying biofilm development.biofilm | community | self-organization | emergent order | nematic order

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Section: Resultsmentioning

confidence: 99%

Architectural transitions in Vibrio cholerae biofilms at single-cell resolution

Drescher

Dunkel

Nadell

et al. 2016

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

181

205

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“…Twisted-bipolar tactoids of cellulose nanocrystals have also been demonstrated recently (10). The emergence of chirality in achiral liquid crystals has fueled the curiosity of scientists ever since their discovery (11,12). There have been a host of technological applications that take advantage of chiral configurations of confined liquid crystals (13,14).…”

mentioning

confidence: 99%

Using chiral tactoids as optical probes to study the aggregation behavior of chromonics

Nayani

Chang

et al. 2017

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

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Tactoids are nuclei of an orientationally ordered nematic phase that emerge upon cooling the isotropic phase. In addition to providing a natural setting for exploring chromonics under confinement, we show that tactoids can also serve as optical probes to delineate the role of temperature and concentration in the aggregation behavior of chromonics. For high concentrations, we observe the commonly reported elongated bipolar tactoids. As the concentration is lowered, breaking of achiral symmetry in the director configuration is observed with a predominance of twisted bipolar tactoids. On further reduction of concentration, a remarkable transformation of the director configuration occurs, wherein it conforms to a unique splay-minimizing configuration. Based on a simple model, we arrive at an interesting result that lower concentrations have longer aggregates at the same reduced temperature. Hence, the splay deformation that scales linearly with the aggregate length becomes prohibitive for lower concentrations and is relieved via twist and bend deformations in this unique configuration. Raman scattering measurements of the order parameters independently verify the trend in aggregate lengths and provide a physical picture of the nematic-biphasic transition.chirality | self-assembly | chromonics | tactoids | phase transitions W hen an isotropic phase of a lyotropic system undergoes a phase transition to an ordered nematic phase, the pathway is usually mediated through spindle-shaped droplets called tactoids. Observation and analysis of tactoids have been an integral part of the investigations on liquid crystals, including some of the earliest experiments that motivated the seminal theory of Onsager (1-3). Tactoids also provide a natural setting to study nematics under confinement (4-6). Hence, they are an attractive setting as a testbed for fundamental research as well as being relevant to technological applications. This has driven the experimental investigation of tactoids in a host of materials, including dispersions of viruses (1, 3), proteins (7), inorganic platelets (8), and lyotropic chromonic liquid crystals (LCLCs) (4).The director configuration in the tactoids is dictated by the individual contribution of the elastic constants, splay (K11), twist (K22), and bend (K33) to the Frank free energy (4, 9). Historically, tactoids of lyotropic nematic liquid crystals have been found to have an elongated shape and adopt a bipolar configuration with the director following the meridional lines (1,8,9). Only recently has a twisted-bipolar director configuration been experimentally realized for a LCLC system when it was crowded with polyethylene glycol (PEG) (4). Twisted-bipolar tactoids of cellulose nanocrystals have also been demonstrated recently (10). The emergence of chirality in achiral liquid crystals has fueled the curiosity of scientists ever since their discovery (11, 12). There have been a host of technological applications that take advantage of chiral configurations of confined liquid crystals (13,14). In thi...

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“…The establishment of helical handedness can be formed at the macro-molecular level due to the stereo-ordering regularity of constituted chiral entities at the intra-molecular and intermolecular interactions [198]. The chirality transfer from the molecular to the supramolecular level (nanometer and micrometer scale) and the morphological level was observed in the inorganic liquid crystals [115], polymers [198], and bio-polymers XXIX including cellulose, sugars, proteins, RNA, and DNA.…”

Section: Cell Membrane (Phospholipids and Cholesterol)mentioning

confidence: 95%

“…XVII The formation of supramolecular helicity is associated with the occurrence of new thermodynamic phases. The chirality related effects in thermotropic and lyotropic liquid crystals were demonstrated through the ferroelectricity [115]. The phase transitions were shown to be implicated in the effects of the chirality transformation and monochirality observed in the amino acids and proteins [119].…”

Section: Chirality Transfermentioning

confidence: 99%