Engineering of Complex Order and the Macroscopic Deformation of Liquid Crystal Polymer Networks

Haan, Laurens T. de; Sánchez‐Somolinos, Carlos; Bastiaansen, Cees M. W.; Schenning, Albertus P. H. J.; Broer, Dirk J.

doi:10.1002/ange.201205964

Cited by 89 publications

(94 citation statements)

References 40 publications

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“…Based on this mechanism, we have developed various surface topographical transformations that are reversibly controlled by light for substrate-constrained glassy LC films. 25,30,31 The high-resolution imprinting of the internal molecular order using photo-alignment command layers provides the possibility to design complex director distributions and material anisotropies, [32][33][34] and allows for miniaturization into the micrometer regime. 26,27,35 In this study, we use a recently-developed optomechanical model 25 to design travelling surface waves under a uniform continuous polarized light source that rotates in time.…”

Section: Introductionmentioning

confidence: 99%

Travelling waves on photo-switchable patterned liquid crystal polymer films directed by rotating polarized light

2019

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Nature employs travelling waves to generate propulsion of fluids, cells and organisms. This has inspired the development of responsive material systems based on different external triggers. Especially lightactuation is suitable because of its remote control and scalability, but often complex, moving light sources are required. Here, we developed a method that only requires flood exposure by rotating the linear polarization of light to generate propagating surface waves on azobenzene-modified liquid crystalline polymer films. We built a photomechanical computational model that accounts for the attenuation of polarized light and trans-to-cis isomerization of azobenzene. A non-uniform in-plane distribution of the liquid crystal molecules allows for the generation of travelling surface waves whose amplitude, speed and direction can be controlled through the intensity, rotation direction and rotation speed of the linear polarization of a light source. Our method opens new avenues for motion control based on light-responsive topographical transformations for application in microfluidic lab-on-chip systems and soft robotics.

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Section: Introductionmentioning

confidence: 99%

Travelling waves on photo-switchable patterned liquid crystal polymer films directed by rotating polarized light

2019

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“…As explained in [5,6,7], the nematic mesogens, whether in LCE or LCG, are responsive to heat and light. When cooled, the mesogens in a chain tend to order and therefore 'lineup' in a single orientation, thus having the effect of elongating the chain by uncoiling the spaghetti-like conformation.…”

Section: Actuation Of Nematic Glass Sheetsmentioning

confidence: 97%

“…The basic engineering design goal of actuation of nematic glass sheets is to determine imprinted director distributions in a flat (or curved) sheet of nematic glass material, in order to achieve particular actuated shapes on exposure to appropriate stimuli. Based on the creative fabrication techniques of Broer, Sanchez-Somolinos and co-workers [5], Modes, Warner and Bhattacharya [6,7] 1 have considered this question in some restricted special cases and in the context of determining the final deformed shapes when the patterned director field in the undeformed flat state is known. The inverse problem, that of determining the undeformed (unactuated) shape and a nematic director distribution on it that results in a known actuated shape, is significantly more difficult [8,9,10] using the techniques that have been employed till date.…”

Section: Introductionmentioning

confidence: 99%

A Design Principle for Actuation of Nematic Glass Sheets

Acharya

2018

J Elast

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A continuum mechanical framework is developed for determining a) the class of stressfree deformed shapes and corresponding director distributions on the undeformed configuration of a nematic glass membrane that has a prescribed spontaneous stretch field and b) the class of undeformed configurations and corresponding director distributions on it resulting in a stress-free given deformed shape of a nematic glass sheet with a prescribed spontaneous stretch field. The proposed solution rests on an understanding of how the Lagrangian dyad of a deformation of a membrane maps into the Eulerian dyad in three dimensional ambient space. Interesting connections between these practical questions of design and the mathematical theory of isometric embeddings of manifolds, deformations between two prescribed Riemannian manifolds, and the slip-line theory of plasticity are pointed out.

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“…Shearing surface force [44], electrical [180] and magnetic fields [61] are all well-known methods for aligning mesogens before initiating polymerisation to preserve this orientation. Photoalignment can create spatially varying responses in two dimensions, demonstrated both continuously [181,182] and using a discrete voxel approach [60]. The development of local feature manipulation in LCEs is reviewed comprehensively by White et al [37].…”

Section: Reproducing Positioning and Orientationmentioning

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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Engineering of Complex Order and the Macroscopic Deformation of Liquid Crystal Polymer Networks

Abstract: Auf‐ oder abwärts: Komplex strukturierte freistehende Polymerfilme mit einer dreidimensionalen molekularen Ordnung wurden durch Photoausrichtung polymerisierbarer Flüssigkristalle hergestellt. Die gebildeten Filme verformen sich beim Erhitzen zu Kegel‐ und Sattelformen.

Cited by 89 publications

References 40 publications

Travelling waves on photo-switchable patterned liquid crystal polymer films directed by rotating polarized light

Travelling waves on photo-switchable patterned liquid crystal polymer films directed by rotating polarized light

A Design Principle for Actuation of Nematic Glass Sheets

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

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