Topological defects of nematic liquid crystals confined in porous networks

Serra, Francesca; Vishnubhatla, Krishna Chaitanya; Buscaglia, Marco; Cerbino, Roberto; Osellame, Roberto; Cerullo, Giulio; Bellini, Tommaso

doi:10.1039/c1sm05813d

Cited by 40 publications

(36 citation statements)

References 26 publications

(38 reference statements)

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“…(2) To find a material which exhibits, at least in some directions, a large ratio between weight and fracture toughness [186][187][188][189][190][191][192][193][194][195]. 3To find a deformable porous material saturated by an electrically or magnetically active nematic fluid, to enhance Darcy dissipation to control the propagation of electro-or magneto-nematic waves [196][197][198][199]. (4) To find an adaptive material endowed with an embedded sensing system activating variations in mechanical constitutive parameters; for example: a beam with a section moment of inertia that can be modified by the actuation driven by mechanical wave propagation or by an electrical signal, or other kinds of smart materials for bone fracture repair purposes [200][201][202][203][204][205][206][207][208][209][210][211][212][213][214].…”

Section: Examples Of Possible Implementations Of the Mission Statementmentioning

confidence: 99%

Synthesis of Fibrous Complex Structures: Designing Microstructure to Deliver Targeted Macroscale Response

Dell’Isola

Steigmann

Corte

2015

Applied Mechanics Reviews

112

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In Mechanics, material properties are most often regarded as being given, and based on this, many technical solutions are usually conceived and constructed. However, nowadays manufacturing processes have advanced to the point that metamaterials having selected properties can be designed and fabricated. Three-dimensional printing, electrospinning, self-assembly, and many other advanced manufacturing techniques are raising a number of scientific questions which must be addressed if the potential of these new technologies is to be fully realized. In this work, we report on the status of modeling and analysis of metamaterials exhibiting a rich and varied macroscopic response conferred by complex microstructures and particularly focus on strongly interacting inextensible or nearly inextensible fibers. The principal aim is to furnish a framework in which the mechanics of 3D rapid prototyping of microstructured lattices and fabrics can be clearly understood and exploited. Moreover, several-related open questions will be identified and discussed, and some methodological considerations of general interest are provided.

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Section: Examples Of Possible Implementations Of the Mission Statementmentioning

confidence: 99%

Synthesis of Fibrous Complex Structures: Designing Microstructure to Deliver Targeted Macroscale Response

Dell’Isola

Steigmann

Corte

2015

Applied Mechanics Reviews

112

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“…An interesting recent development, very different from display applications where defects must be avoided at any price, is the research on well-controlled defect configurations and ways of applying them. [1][2][3][4][5][6][7][8][9][10][11][12] A fascinating special case is given by LC droplets 13,14 and shells 15,16 since the spherical topology in combination with planar alignment (director n in the plane of the drop/shell surface) ensures specific configurations of topo- logical defects (disclinations) on the surface, 17 always with a net sum s = 2. The parameter s is the winding number that specifies how many full turns the director (or its projection on the surface) rotates around a defect.…”

Section: Introductionmentioning

confidence: 99%

Towards tunable defect arrangements in smectic liquid crystal shells utilizing the nematic–smectic transition in hybrid-aligned geometries

et al. 2012

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We produce and investigate liquid crystal shells with hybrid alignment-planar at one boundary, homeotropic at the otherundergoing a transition between the nematic (N) and smectic-A (SmA) phases. The shells display a dynamic sequence of patterns, the details depending on the alignment agents and on the diameter and thickness of the shell. In shells of sufficient diameter we typically find a transient striped texture near the N-SmA transition, stabilising into a pattern of tiled, more or less regularly spaced focal conic domains in the SmA phase. The domain size and spacing decrease with reduced shell thickness. In case of strong homeotropic anchoring at one boundary and small shell size, however, the increased curvature favors homeotropic against planar alignment in the smectic phase, and the shell then tends to adapt complete homeotropic alignment at the final stage of the transition. This is the first study of hybrid-aligned smectic shells and the results constitute a beautiful demonstration of the capacity for dynamic structure formation and reformation via self-assembly in soft matter. The new patterns extend the range of arrays of topological defects that can be realised with liquid crystals in spherical morphology and the correlation between the feature arrangements and the variable parameters of the shell and its environment opens a route towards tunability. However, the observed strong impact from increasing curvature, even for these rather large shells, indicates that the choice of alignment agents inducing planar or homeotropic alignment with varying strength will become critical when targeting the most attractive colloidal size scale of about a micron or smaller.

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“…Studies of liquid-crystalline textures of small molecules confined to volumes of differing micro-/nano-size, shape, and topology (e.g. droplets [7,8] to 3D periodic networks [9]) show that such textures are highly dependent on the shape of the confining volume, orientational symmetries of the ordered phases [10,11], and, crucially, the anchoring of alignment at the confining surface [12]. Analogous alignment may be expected from the spontaneously formed interface between unlike components, posing a basic question, do segments align parallel (homogeneous) or normal (homeotropic) to inter-domain surfaces?…”

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confidence: 99%

Intradomain Textures in Block Copolymers: Multizone Alignment and Biaxiality

et al. 2017

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Block copolymer (BCP) melt assembly has been the subject of decades of study, with focus largely on self-organized spatial patterns of periodically-ordered segment density. In this study, we demonstrate that underlying these otherwise well-known composition profiles (i.e. ordered lamella, cylinders, spheres and networks) are generic and heterogeneous patterns of segment orientation that couple strongly to morphology, even in the absence of specific factors that promote intra-or inter-chain segment alignment. We employ a combination of self-consistent field theory and coarse-grained simulation methods to measure polar and nematic order parameters of segments in a freely-jointed chain model of diblock melts. We show that BCP morphologies are generically characterized by a multizone texture, with segments predominantly aligned normal and parallel to inter-domain interfaces in the respective brush and interfacial regions of the microdomain. Further, morphologies with anisotropically-curved interfaces (i.e. cylinders and networks) exhibit biaxial order that is aligned to the principal curvature axes of the interface. Understanding these generic features of intra-domain texture provide new opportunities for manipulating multi-scale structure and functional properties of BCP assembly.

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Topological defects of nematic liquid crystals confined in porous networks

Cited by 40 publications

References 26 publications

Synthesis of Fibrous Complex Structures: Designing Microstructure to Deliver Targeted Macroscale Response

Synthesis of Fibrous Complex Structures: Designing Microstructure to Deliver Targeted Macroscale Response

Towards tunable defect arrangements in smectic liquid crystal shells utilizing the nematic–smectic transition in hybrid-aligned geometries

Intradomain Textures in Block Copolymers: Multizone Alignment and Biaxiality

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