Macroscopic dynamics of polar nematic liquid crystals

Brand, Helmut R.; Pleiner, Harald; Ziebert, Falko

doi:10.1103/physreve.74.021713

Cited by 30 publications

(35 citation statements)

References 55 publications

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“…[33][34][35][36][37] The coupling between these two elds is inspired by the underlying biological processes: 15 actin is nucleated close to the membrane,{ with a rate b. On the other hand, existing actin that is polymerizing locally pushes against the membrane and advects it, with a rate a.…”

Section: Brief Description Of the Modelmentioning

confidence: 99%

Modeling crawling cell movement on soft engineered substrates

2014

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Self-propelled motion, emerging spontaneously or in response to external cues, is a hallmark of living organisms. Systems of self-propelled synthetic particles are also relevant for multiple applications, from targeted drug delivery to the design of self-healing materials. Self-propulsion relies on the force transfer to the surrounding. While self-propelled swimming in the bulk of liquids is fairly well characterized, many open questions remain in our understanding of self-propelled motion along substrates, such as in the case of crawling cells or related biomimetic objects. How is the force transfer organized and how does it interplay with the deformability of the moving object and the substrate? How do the spatially dependent traction distribution and adhesion dynamics give rise to complex cell behavior? How can we engineer a specific cell response on synthetic compliant substrates? Here we generalize our recently developed model for a crawling cell by incorporating locally resolved traction forces and substrate deformations.The model captures the generic structure of the traction force distribution and faithfully reproduces experimental observations, like the response of a cell on a gradient in substrate elasticity (durotaxis). It also exhibits complex modes of cell movement such as "bipedal" motion. Our work may guide experiments on cell traction force microscopy and substrate-based cell sorting and can be helpful for the design of biomimetic "crawlers" and active and reconfigurable self-healing materials.

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Section: Brief Description Of the Modelmentioning

confidence: 99%

Modeling crawling cell movement on soft engineered substrates

2014

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“…[117][118][119] There it is assumed that the droplet contains some sort of 'active gel' material that can be described by a polarisation vector p (or alternatively by a tensorial nematic order parameter Q). The evolution of the polarisation field p follows an equation for polar liquid crystals, 120,121 generalised by active reactions 108,109 and coupled to the hydrodynamic flow field v (cf. Marth et al 117 and Tjhung et al 118 ).…”

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confidence: 99%

Computational approaches to substrate-based cell motility

Ziebert

Aranson

2016

npj Comput Mater

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Substrate-based crawling motility of eukaryotic cells is essential for many biological functions, both in developing and mature organisms. Motility dysfunctions are involved in several life-threatening pathologies such as cancer and metastasis. Motile cells are also a natural realisation of active, self-propelled 'particles', a popular research topic in nonequilibrium physics. Finally, from the materials perspective, assemblies of motile cells and evolving tissues constitute a class of adaptive self-healing materials that respond to the topography, elasticity and surface chemistry of the environment and react to external stimuli. Although a comprehensive understanding of substrate-based cell motility remains elusive, progress has been achieved recently in its modelling on the whole-cell level. Here we survey the most recent advances in computational approaches to cell movement and demonstrate how these models improve our understanding of complex self-organised systems such as living cells.

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“…It turns out that all reversible crosscoupling arising and listed in eqs. (36)- (38) and (40)- (43) have been presented before for nematic gels [28] or for low molecular weight polar nematic liquid crystals [27,48]. We refer to these references for a more detailed analysis.…”

Section: Reversible Cross-coupling Termsmentioning

confidence: 99%

“…Here ν ijkl is the uniaxial viscosity tensor [19] [27]. All terms associated with ξ px are characteristic for systems with a polar direction and do not arise for non-polar liquid crystals.…”

Section: Irreversible Dynamics and Entropy Productionmentioning

confidence: 99%

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Macroscopic behavior of polar nematic gels and elastomers

2016

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Abstract. We present the derivation of the macroscopic equations for uniaxial polar nematic gels and elastomers. We include the strain field as well as relative rotations as independent dynamic macroscopic degrees of freedom. As a consequence, special emphasis is laid on possible static and dynamic cross-couplings between these macroscopic degrees of freedom associated with the network, and the other macroscopic degrees of freedom including reorientations of the macroscopic polarization. In particular, we find static and dissipative dynamic cross-couplings between strain fields and relative rotations on one hand and the macroscopic polarization on the other that allow for new possibilities to manipulate polar nematics. To give one example each for the effects of a static and a dissipative cross-coupling: we find that a static electric field applied perpendicularly to the polar preferred direction leads to relative rotations while dynamically relative rotations can lead to transverse electric currents. In addition to a permanent network, we also consider the effect of a transient network, which is particularly important for the case of gels, melts and concentrated polymer solutions. A section on the influence of macroscopic chirality is included as well.

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Macroscopic dynamics of polar nematic liquid crystals

Cited by 30 publications

References 55 publications

Modeling crawling cell movement on soft engineered substrates

Modeling crawling cell movement on soft engineered substrates

Computational approaches to substrate-based cell motility

Macroscopic behavior of polar nematic gels and elastomers

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