Programmed morphing of liquid crystal networks

Haan, Laurens T. de; Schenning, Albert P. H. J.; Broer, Dirk J.

doi:10.1016/j.polymer.2014.08.023

Cited by 129 publications

(136 citation statements)

References 69 publications

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“…[19] The light-triggered deformation of an LCN actuator is governed by the alignment distribution of the constituent liquid-crystal molecules within the polymer network, and developing methods for precise control over the director distribution in order to obtain desired photoactuation mode is an important topic of research. [14,[20][21][22] Photoalignment has proven to be a successful technique in patterning complex alignments into liquid-crystalline materials [23][24][25] and in devising on-demand actuations into LCNs. [21] The technique is based on illuminating a thin photoresponsive layer, a "command surface," [26] with linearly polarized light.…”

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confidence: 99%

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Wani

Zeng

Wasylczyk

et al. 2017

Advanced Optical Materials

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have emerged as promising materials for fabricating soft actuators. [12][13][14] LCNs combine the anisotropy of the constituent liquid-crystal (LC) molecules and the elasticity of polymer networks, and are capable of stimuli-responsive shape change at the macroscopic scale. LCNs can be actuated by various stimuli such as light, [15] heat, [16] solvent, [17] and humidity. [18] Being a clean, remote, and precisely controllable stimulus, light is a particularly attractive energy source. [19] The light-triggered deformation of an LCN actuator is governed by the alignment distribution of the constituent liquid-crystal molecules within the polymer network, and developing methods for precise control over the director distribution in order to obtain desired photoactuation mode is an important topic of research. [14,[20][21][22] Photoalignment has proven to be a successful technique in patterning complex alignments into liquid-crystalline materials [23][24][25] and in devising on-demand actuations into LCNs. [21] The technique is based on illuminating a thin photoresponsive layer, a "command surface," [26] with linearly polarized light. Upon illumination, the photoalignment layer becomes anisotropic, thereby changing the boundary conditions experienced by the liquid-crystal molecules in the vicinity, and forcing them to align either perpendicular [27] or parallel [28] to the light polarization. Photopatterning of director orientation can be achieved by spatially modulating the light polarization, [27] or exposure through mask(s). [28,29] White and co-workers have used a laser setup to raster scan a focussed laser beam with controlled polarization across the sample, and thus achieved local control in the director distribution. [30][31][32] Also spatial light modulators and digital micromirror devices have been used for high-throughput patterning. [17,[33][34][35] These demonstrations require either prepatterned masks or relatively complex optical set-ups for programming the desired director distribution.Herein, we use a laser projector with a microelectromechanical system (MEMS)-based scanning mirror assembly (PICO, Sony) to program the liquid-crystal alignment within a monolithic LCN film. Photopatterning is achieved by projecting an arbitrary computer-generated image onto the photoalignment layer, using predefined light polarization. The projector is capable of addressing a minimum feature size of 50 µm over an area of 25 × 14 mm 2 . A series of complex photoactuators, such as defect buckling, coiling strip with gradient in pitch, four-arm gripper, and bidirectional bending in an octopod, are demonstrated by engineering different director orientations via photopatterning. The photoactuators are fabricated by polymerizing LC monomer mixtures inside LC cells that have been A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relative...

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confidence: 99%

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Wani

Zeng

Wasylczyk

et al. 2017

Advanced Optical Materials

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“…This may be constant throughout a material, creating simple uniaxial deformation of up to 300 %, or vary in orientation creating twists [58] and out of plane effects [59]. Programmable orientation of the director in discrete volume elements across an LCE was demonstrated in 2015, unlocking arbitrary deformation through 'voxelation' [60].…”

Section: Skeletal Muscle-active Contractionmentioning

confidence: 99%

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

2016

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Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials-skeletal muscle, tendons and plant tissues-and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.

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“…Experimentalists became adept at imposing a desired orientation on a liquid-crystalline film, either optically [16,17] or by surface relief grating [18], before it is polymerised into an elastic structure. The various shapes have been produced by heating the frozen texture above the NIT point [19][20][21][22]. Reversible transitions of this kind were used for the construction of artificial walkers [23,24].…”

Section: Introductionmentioning

confidence: 99%

Textures and shapes in nematic elastomers under the action of dopant concentration gradients

Zakharov

Pismen

2017

Soft Matter

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We explore a novel strategy of patterning nematic elastomers that does not require inscribing the texture directly. It is based on varying the dopant concentration that, beside shifting the phase transition point, affects the nematic director field via coupling between the gradients of concentration and nematic order parameter. Rotation of the director around a point dopant source causes topological modification manifesting itself in a change of the number of defects. A variety of shapes, dependent on the dopant distribution, are obtained by anisotropic deformation following the nematic-isotropic transition.

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Programmed morphing of liquid crystal networks

Cited by 129 publications

References 69 publications

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Programming Photoresponse in Liquid Crystal Polymer Actuators with Laser Projector

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

Textures and shapes in nematic elastomers under the action of dopant concentration gradients

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