Tapered elasticæ as a route for axisymmetric morphing structures

Liu, Mingchao; Domino, Lucie; Vella, Dominic

doi:10.1039/d0sm00714e

Cited by 44 publications

(27 citation statements)

References 46 publications

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“…The ability to change shape is as important to an emerging class of engineering applications as it is to biological organisms: just as animals and plants morph in response to external stimuli, soft robots must be able to change shape to adapt different environments and complete different tasks [1][2][3]. In both cases, our understanding of different artificial mechanisms through which this shape change can be achieved has exploded in recent years with examples including pneumatic inflation [4,5], multi-material 4D printing [6], magneto-responsive elastomers [7] and 3D-printed composites [8], designed director fields within liquid crystal elastomers [9] and designed cuts in planar sheets [10,11].…”

Section: Introductionmentioning

confidence: 99%

Frustrating frustration in snap-induced morphing

Liu¹,

Domino²,

Dinechin³

et al. 2021

Preprint

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The bistability of embedded elements provides a natural route through which to introduce reprogrammability to elastic meta-materials. However, attempts to leverage this programmability in objects that can change shape, or morph, have been limited by the tendency for the deformations induced by multiple elastic elements to be incompatible -deformation is frustrated by geometry. We study the root cause of this frustration in a particular system, the soft morphable sheet, which is caused by an azimuthal buckling instability of bistable elements embedded within a sheet. With this understanding we show that, for this system at least, the root of frustration can itself be frustrated by an appropriate design of the lattice on which bistable elements are placed.

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Section: Introductionmentioning

confidence: 99%

Frustrating frustration in snap-induced morphing

Liu¹,

Domino²,

Dinechin³

et al. 2021

Preprint

Self Cite

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“…In the case of the ribbon in C3 with a length of and a thickness of , the narrower end only bends around the transverse axis (uniaxial bending), while the conformation at the wider end gets controlled by the longitudinal and transverse axis (biaxial bending). This approach to data presentation was derived from the consideration that the 2D spiral should be controlled by the gradient in curvature and, as the ribbon width is increased, bending in the transverse direction plays an increasing role and results in an apparent stiffening of the ribbon [ 30 ], which we consider to be proportional to the gradient in width [ 31 ]. So far, we limit our analysis of the bending of the wedge like ribbons to the description of the experimental observation.…”

Section: Resultsmentioning

confidence: 99%

Microgel that swims to the beat of light

et al. 2021

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Complementary to the quickly advancing understanding of the swimming of microorganisms, we demonstrate rather simple design principles for systems that can mimic swimming by body shape deformation. For this purpose, we developed a microswimmer that could be actuated and controlled by fast temperature changes through pulsed infrared light irradiation. The construction of the microswimmer has the following features: (i) it is a bilayer ribbon with a length of 80 or 120 $$\upmu $$ μ m, consisting of a thermo-responsive hydrogel of poly-N-isopropylamide coated with a 2-nm layer of gold and equipped with homogeneously dispersed gold nanorods; (ii) the width of the ribbon is linearly tapered with a wider end of 5 $$\upmu $$ μ m and a tip of 0.5 $$\upmu $$ μ m; (iii) a thickness of only 1 and 2 $$\upmu $$ μ m that ensures a maximum variation of the cross section of the ribbon along its length from square to rectangular. These wedge-shaped ribbons form conical helices when the hydrogel is swollen in cold water and extend to a filament-like object when the temperature is raised above the volume phase transition of the hydrogel at $$32\,^{\circ } \hbox {C}$$ 32 ∘ C . The two ends of these ribbons undergo different but coupled modes of motion upon fast temperature cycling through plasmonic heating of the gel-objects from inside. Proper choice of the IR-light pulse sequence caused the ribbons to move at a rate of 6 body length/s (500 $$\upmu $$ μ m/s) with the wider end ahead. Within the confinement of rectangular container of 30 $$\upmu $$ μ m height and 300 $$\upmu $$ μ m width, the different modes can be actuated in a way that the movement is directed by the energy input between spinning on the spot and fast forward locomotion. Graphic abstract

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“…One way to easily construct spatial shapes from flat sheets is by appropriately folding paper [Dudte et al 2016;Massarwi et al 2007], which is inherently related to the Japanese art of Origami. Also Kirigami, a technique to cut patterns into planar sheets to allow solid faces to rotate about each other, deforming in three dimensions while remaining planar has been explored for deployable surfaces [Jiang et al 2020;Liu et al 2020] and recently also bi-stable structures .…”

Section: Related Workmentioning

confidence: 99%

Generalized deployable elastic geodesic grids

Pillwein

Weiss²

2021

ACM Trans. Graph.

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Given a designer created free-form surface in 3d space, our method computes a grid composed of elastic elements which are completely planar and straight. Only by fixing the ends of the planar elements to appropriate locations, the 2d grid bends and approximates the given 3d surface. Our method is based purely on the notions from differential geometry of curves and surfaces and avoids any physical simulations. In particular, we introduce a well-defined elastic grid energy functional that allows identifying networks of curves that minimize the bending energy and at the same time nestle to the provided input surface well. Further, we generalize the concept of such grids to cases where the surface boundary does not need to be convex, which allows for the creation of sophisticated and visually pleasing shapes. The algorithm finally ensures that the 2d grid is perfectly planar, making the resulting gridshells inexpensive, easy to fabricate, transport, assemble, and finally also to deploy. Additionally, since the whole structure is pre-strained, it also comes with load-bearing capabilities. We evaluate our method using physical simulation and we also provide a full fabrication pipeline for desktop-size models and present multiple examples of surfaces with elliptic and hyperbolic curvature regions. Our method is meant as a tool for quick prototyping for designers, architects, and engineers since it is very fast and results can be obtained in a matter of seconds.

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Tapered elasticæ as a route for axisymmetric morphing structures

Abstract: Transforming flat two-dimensional (2D) sheets into three-dimensional (3D) structures by combining carefully made cuts with applied edge-loads has emerged as an exciting manufacturing paradigm in a range of applications from...

Cited by 44 publications

References 46 publications

Frustrating frustration in snap-induced morphing

Frustrating frustration in snap-induced morphing

Microgel that swims to the beat of light

Generalized deployable elastic geodesic grids

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