We describe reshaping of active textiles actuated by bending of Janus fibres comprising both active and passive components. A great variety of shapes, determined by minimising the overall energy of the fabric, can be produced by varying bending directions determined by the orientation of Janus fibres. Under certain conditions, alternative equilibrium states, one absolutely stable and the other metastable coexist, and their relative energy may flip its sign as system parameters, such as the extension upon actuation, change. A snap-through reshaping in a specially structured textile reproduces the Venus flytrap effect.
We consider three-dimensional reshaping of thin nemato-elastic sheets containing half-charged defects upon nematic-isotropic transition. Gaussian curvature, that can be evaluated analytically when the nematic texture is known, differs from zero in the entire domain and has a dipole or hexapole singularity, respectively, at defects of positive or negative sign. The latter kind of defects appears in not simply connected domains. Three-dimensional shapes dependent on boundary anchoring are obtained with the help of finite element computations.Liquid crystal elastomers and glasses [1], made of crosslinked polymeric chains with embedded mesogenic structures, combine orientational properties of liquid crystals with shear strength of solids, and were envisaged by de Gennes as prototype artificial muscles [2]. Their specific feature is a strong coupling between the director orientation and mechanical deformations, which can be controlled by the various physical and chemical agents. When the material undergoes a phase transition from the isotropic to nematic state, it strongly elongates along the director and, accordingly, shrinks in the normal direction to preserve its volume; the opposite effect takes place as result of the reverse transition. Stresses arising due to these intrinsic deformations were investigated for flat sheets where they were shown to lead to phase separation of isotropic and nematic domains [3] or formation of persistent defects that are not necessitated by topology [4].Internal stresses can be relaxed when three-dimensional (3D) deformations are allowed. The reshaping effect causes bending of flat thin sheets into curved shells. Aharoni et al [5] studied the various nematic textures that can be impressed in the material to induce a desired two-dimensional (2D) metric that would determine a 3D shape upon transition from nematic to isotropic state (NIT). This opens the way to construct surfaces with nonzero Gaussian curvature out of flat sheets with no stretching [6], or, more generally, to change the Gaussian curvature of shells. While the Gaussian curvature is an intrinsic property that can be computed based a surface metric only [7], computing an actual 3D shape is a far more challenging task, which is still more complicated by constraints on nematic tissues imposed by boundary conditions or topology of closed manifolds that necessitate emergence of defects. A 3D shape can be computed analytically only for a symmetric texture, and the only available example is deformation of a circle containing a defect with unit circulation into a cone or an anticone [6,8]. This case is exceptional in two respects. First, the natural nematic texture induced within a circle by either tangential or normal boundary anchoring contains two halfcharged defects which have a lower energy than a single defect of unit charge. Second, the Gaussian curvature induced by a unit charge defect vanishes everywhere except the vicinity of the defect itself [5], where it can be regularized either by local stretching [6] or by the de...
Morphogenetic dynamics of tissue sheets require coordinated cell shape changes regulated by global patterning of mechanical forces. Inspired by such biological phenomena, we propose a minimal mechanochemical model based on...
We consider the reshaping of closed Janus filaments acquiring intrinsic curvature upon actuation of a driven component-a nematic elastomer elongating upon phase transition. Linear stability analysis establishes instability thresholds of circles with no imposed twist, dependent on the ratio q of the intrinsic curvature to the inverse radius of the original circle. Twisted circles are proven to be absolutely unstable but the linear analysis well predicts the dependence of the looping number of the emerging configurations on the imposed twist. Modeling stable configurations by relaxing numerically the overall elastic energy detects multiple stable and metastable states with different looping numbers. The bifurcation of untwisted circles turns out to be subcritical, so that nonplanar shapes with a lower energy exist at q below the critical value. The looping number of stable shapes generally increases with q.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.