Shape-responsive liquid crystal elastomer bilayers

Agrawal, Alpna; Yun, TaeHyun; Pesek, Stacy L.; Chapman, Walter G.; Verduzco, Rafael

doi:10.1039/c3sm51654g

Cited by 92 publications

(82 citation statements)

References 45 publications

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“…Crosslinked liquid crystalline polymers (LCPs) have received much attention as candidates for this purpose since they can exhibit large macroscopic scale mechanical response to different external stimuli such as heat, light, pH, or moisture . Thin‐films of these materials with controlled molecular orientation, defined by the director ( n ), have predominantly been investigated as building blocks to implement a variety of responsive elements or devices .…”

Section: Introductionmentioning

confidence: 99%

4D Printed Actuators with Soft‐Robotic Functions

López-Valdeolivas

Liu

Broer

et al. 2017

Macromol. Rapid Commun.

291

307

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troactive polymers, [7] as well as patterned hydrogels that shape-shift on swelling. [8,9] Further development of soft elements capable to perform complex motions or functions requires adequate materials and processing technologies that enable accurate control of the mechanical response. Moreover, on the route toward practical applications, there is often a necessity to have the possibility to miniaturize these elements, produce them in large dimensions or over large areas, or integrate them with other materials, elements, or devices.Crosslinked liquid crystalline polymers (LCPs) have received much attention as candidates for this purpose since they can exhibit large macroscopic scale mechanical response to different external stimuli such as heat, light, pH, or moisture. [10][11][12] Thinfilms of these materials with controlled molecular orientation, defined by the director (n), have predominantly been investigated as building blocks to implement a variety of responsive elements or devices. [13][14][15][16][17][18][19][20][21][22] However the thinfilm character of these elements markedly limits the energy available for actuation. Even more, the reported systems, including their processing toolbox, are limited to one single material and therefore multifunctional and multiresponsive systems are difficult to create. For the true development and incorporation of these LCP structures in real life applications, the capability to generate elements of different sizes, from very small to very large, is fundamental. This needs to be done with a precise control of the material morphology and properties as well as director orientation in well-defined complex geometries, all together leading to an accurate control of the mechanical response.Additive manufacturing techniques enable digital generation of material patterns in surfaces or fabrication of 3D objects. While 3D printing of conventional materials leads to inanimate 3D objects with static shape, 4D printing of responsive materials adds a 4th dimension as it leads to architectures that, with an appropriate stimulus, change their shape over time. [9,23] Here, we report the 4D printing of liquid crystalline elastomer (LCE) macro-and microstructures. Digital control of the local anisotropy of the applied LC material is advantageously achieved through the printing process. This allows to precisely program the magnitude and directionality of the forces in response to the external stimulus, temperature in our case, and therefore well-defined reversible shape-morphing of the structures in space and time. Although 4D printing has been recently described with hydrogels charged with anisotropic cellulose fibrils that get oriented during printing, [9] the mechanical response of these materials is based on water swelling, which limits the applicability due to the specific and stringent environment required for actuation as well as the slow response 3D Printing Soft matter elements undergoing programed, reversible shape change can contribute to fundamental advance in areas such as ...

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Section: Introductionmentioning

confidence: 99%

4D Printed Actuators with Soft‐Robotic Functions

López-Valdeolivas

Liu

Broer

et al. 2017

Macromol. Rapid Commun.

291

307

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“…When macroscopically aligned, such materials also exhibit large dimensional changes, making them interesting as actuating polymers. Both stimulus‐responsive free standing films as well as LCEs confined to a solid substrate have been reported with programmable shapes and topographies . For CLC elastomers, dimensional changes along the helical pitch direction even resulted in changes in reflective color .…”

Section: Introductionmentioning

confidence: 99%

“…Both stimulus-responsive free standing films as well as LCEs confined to a solid substrate have been reported with programmable shapes and topographies. [27][28][29][30][31][32][33][34][35][36][37][38][39] For CLC elastomers, dimensional changes along the helical pitch direction even resulted in changes in reflective color. [40][41][42][43] However, simultaneously changing both the topography and reflectivity by one stimulus remains a challenge.…”

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confidence: 99%

Easily Processable and Programmable Responsive Semi‐Interpenetrating Liquid Crystalline Polymer Network Coatings with Changing Reflectivities and Surface Topographies

Kragt

Broer

Schenning

2017

Adv Funct Materials

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The fabrication of stimulus-responsive coatings that change both reflectivity and topography is hampered by the lack of easy processable, patternable, and programmable elastomers. Here, an easily applied reflective coating based on a semi-interpenetrating polymer network composed of a liquid crystal elastomer and a liquid crystal network (>15 wt%) is reported. The reflective wavelength of these polysiloxane elastomer photonic coatings can be readily programed by the concentration of chiral reactive mesogen dopant that forms the network. The coatings show a fast and reversible decrease in reflection band intensity with increasing temperature, which can be tuned by the polymer network density. In addition, hierarchical surface relief structures are prepared, which can be reversibly changed with temperature.

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“…The bilayer device consisted of a passive silicone polymer layer and a SWCNT‐doped LCE layer that efficiently converted IR energy into heat, causing shrinking of the LCE along the long axis and bending of the bilayer film due to the bulk LCE nematic ‐isotropic phase transition. Agrawal et al also used a bilayer strategy to convert uniaxially aligned LCEs into 3D actuators . Another strategy to create LCE actuators capable of complex shape change without complex alignment is to spatially control the stimulus response of a film.…”

Section: Applications Of Lcesmentioning

confidence: 99%

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

Kularatne

Kim

Boothby

et al. 2017

J Polym Sci B Polym Phys

288

232

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Liquid crystal elastomers (LCEs) are a unique class of materials which combine rubber elasticity with the orientational order of liquid crystals. This combination can lead to materials with unique properties such as thermal actuation, anisotropic swelling, and soft elasticity. As such, LCEs are a promising class of materials for applications requiring stimulus response. These unique features and the recent developments of the LCE chemistry and processing will be discussed in this review. First, we emphasize several different synthetic pathways in conjunction with the alignment techniques utilized to obtain monodomain LCEs. We then identify the synthesis and alignment techniques used to synthesis LCE-based composites. Finally, we discuss how these materials are used as actuators and sensors.

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Shape-responsive liquid crystal elastomer bilayers

Cited by 92 publications

References 45 publications

4D Printed Actuators with Soft‐Robotic Functions

4D Printed Actuators with Soft‐Robotic Functions

Easily Processable and Programmable Responsive Semi‐Interpenetrating Liquid Crystalline Polymer Network Coatings with Changing Reflectivities and Surface Topographies

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

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