Patterning nonisometric origami in nematic elastomer sheets

Abstract

Nematic elastomers dramatically change their shape in response to diverse stimuli including light and heat. In this paper, we provide a systematic framework for the design of complex three dimensional shapes through the actuation of heterogeneously patterned nematic elastomer sheets. These sheets are composed of nonisometric origami building blocks which, when appropriately linked together, can actuate into a diverse array of three dimensional faceted shapes. We demonstrate both theoretically and experimentally that the nonisometric origami building blocks actuate in the predicted manner, and that the integration of multiple building blocks leads to complex, yet predictable and robust, shapes. We then show that this experimentally realized functionality enables a rich design landscape for actuation using nematic elastomers. We highlight this landscape through examples, which utilize large arrays of these building blocks to realize a desired three dimensional origami shape. In combination, these results amount to an engineering design principle, which provides a template for the programming of arbitrarily complex three dimensional shapes on demand.

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

“…[ 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 in‐plane director orientation field to generate a desired profile of Gaussian curvature, [ 14–17 ] 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.…”

Contrasting bending energies from bulk elastic theories

“…We may now evaluate the forms of the energy density E from (10) that take as input the axial component of the four strains (5-8) containing the bulk axial stretch (11). For each density, this will result in quadratic terms involving one of the four corresponding mid-line strains ε(x), namely…”

“…Much recent work in soft matter mechanics has explored the interplay of stretching and bending elasticity in incompatible plates and shells composed of isotropic gels or elastomers, or nematic solids [1][2][3][4][5]. This subject has inspired, among other things, fundamental questions about embeddings [6][7][8], design principles for shape-programmable materials [9][10][11][12], and insight into the complex shapes of leaves and torn plastic trash bags [13,14].…”

Design of Soft Origami Mechanisms with Targeted Symmetries

“…Folding motions have also been demonstrated in reprogrammable SMP systems based on shifting of the polymer glass transition temperature through local protonation/de-protonation of the polymer film [15]. Reversible actuating materials, such as shape memory alloys [7,16] and liquid crystal elastomers [17,18], have also been utilized for self-folding. Hydrogel-based self-folding materials have extended origami utility into the ultrasoft regimes, as demonstrated by photo-crosslinkable hydrogel hinges with programmable swelling [19].…”