The biomechanical role of extra-axonemal structures in shaping the flagellar beat of Euglena

Cicconofri, Giancarlo; Noselli, Giovanni; DeSimone, Antonio

doi:10.1101/2020.03.15.991331

Cited by 2 publications

(3 citation statements)

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“…Furthermore, smooth variations in deformation can be programmed via grayscale patterning of AuNP absorbance to yield more complex shape changes. Finite element method (FEM) simulations are used to help understand the shapes selected by these materials, in concert with an analytical model based on the principles of Gaussian morphing [ 4,47–49 ] that provides a general approach to the design of axisymmetric shapes through unidirectionally varying stretch profiles.…”

Section: Figurementioning

confidence: 99%

“…To model these shape changes geometrically, we turn to the principle of Gaussian morphing, [ 48,49 ] previously exploited for isotropic systems, and apply it to the anisotropic case considered here. In this model, the in‐plane deformation due to photothermal heat generation defines a “target metric” that describes how the distance between points in the flat sheet should change upon deployment to generate a shape of defined curvature.…”

Section: Figurementioning

confidence: 99%

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Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

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studies have focused on programming desired 3D structures of soft materials such as shape-memory polymers [2,3] and gels [4][5][6][7] by introducing spatial variations in thermal expansion/contraction, swelling, or molecular order. [8] A particularly useful class of materials to achieve dynamic 2D to 3D shape transformations are liquid crystal elastomers (LCEs), where the coupling between the orientational ordering of polymerized mesogens and the conformation of a polymer backbone can be leveraged for large, anisotropic deformations that are dictated by the director field. [9,10] Using oriented surface alignment layers [11] or microchannels, [12] director orientation can be patterned with a resolution approaching 10 µm. [13] A subsequent reduction of nematic ordering, usually driven by heating, leads to local contraction along the director and expansion along the transverse directions, driving out-of-plane buckling into 3D shapes that are "blueprinted" by the pattern of director orientation. However, while geometric methods allow for the deduction of the necessary inplane director orientation field to generate a desired profile of Gaussian curvature, [14][15][16][17] there are a number of practical drawbacks to this approach. First, prescription of complex director fields requires significant processing, making high-throughput fabrication, and evaluation of designs challenging. Additionally, the surface alignment methods needed to specify director orientation with high spatial resolution are only amenable to certain chemistries due to the need for high mesogen content, and thus cannot be widely generalized to all LCE systems. For example, while classical LCE systems based on siloxanes, [18,19] as well as recently developed systems that rely on simple and efficient "click" chemistries, [20] offer attractive thermal and mechanical properties for shape-morphing systems, they typically only allow for alignment of the director field with coarse spatial resolution such as through application of shear stress [21][22][23] or magnetic fields. [24] To circumvent the need for a spatially varying director orientation, where the direction of deformation varies but the magnitude is constant, a potential alternative method to drive shape changes is to instead locally prescribe the magnitude of deformation within an otherwise homogeneous director field. While spatial variations in the extent of deformation have been widely employed for shape Liquid crystal elastomers (LCEs) are an attractive platform for dynamic shape-morphing due to their ability to rapidly undergo large deformations. While recent work has focused on patterning the director orientation field to achieve desired target shapes, this strategy cannot be generalized to material systems where high-resolution surface alignment is impractical. Instead of programming the local orientation of anisotropic deformation, an alternative strategy for prescribed shape-morphing by programming the magnitude of stretch ratio in a thin LCE sheet with constant director orientation is...

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

et al. 2020

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“…Many biological structures can be modeled as tubular assemblies of helical rods, such as the tail sheaths of bacteriophage viruses [1,2], the cellulose filaments in the tendrils of climbing plants [3], the bundles of microtubules and motors in all eukaryotic flagella and cilia [4,5], the envelopes of shapeshifting unicellular organisms such as Lacrymaria Olor [6] and the pellicle of euglenids, a family of unicellular algae [7][8][9][10] (see Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

2021

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Nature and technology often adopt structures that can be described as tubular helical assemblies. However, the role and mechanisms of these structures remain elusive. In this paper, we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods, arranged in pairs with opposite chirality and connected by pin joints, both analytically and numerically. We first focus on compression and find that, whereas a single helical rod would buckle, the rods of the assembly deform coherently as stable helical shapes wound around a common axis. Moreover, we investigate the response of the assembly under different boundary conditions, highlighting the emergence of a central region where rods remain circular helices. Secondly, we study the effects of different hypotheses on the elastic properties of rods, i.e., stress-free rods when straight versus when circular helices, Kirchhoff’s rod model versus Sadowsky’s ribbon model. Summing up, our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods, as well as some interesting features, and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology. Graphic Abstract We study the mechanical response under compression/extension of an assembly composed of 8 helical rods, pin-jointed and arranged in pairs with opposite chirality. In compression we find that, whereas a single rod buckles (a), the rods of the assembly deform as stable helical shapes (b). We investigate the effect of different boundary conditions and elastic properties on the mechanical response, and find that the deformed geometries exhibit a common central region where rods remain circular helices. Our findings highlight the key role of mutual interactions in the ensemble response and shed some light on the reasons why tubular helical assemblies are so common and persistent.

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The biomechanical role of extra-axonemal structures in shaping the flagellar beat of Euglena

Cited by 2 publications

References 36 publications

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

Mechanics of tubular helical assemblies: ensemble response to axial compression and extension

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