Mechanically programmed 2D and 3D liquid crystal elastomers at macro- and microscale <i>via</i> two-step photocrosslinking

Lee, Jieun; Guo, Yiting; Choi, Yu‐Jin; Jung, Soonho; Seol, Daehee; Choi, Subi; Kim, Jae Hong; Kim, Yunseok; Jeong, Kwang‐Un; Ahn, Suk‐kyun

doi:10.1039/c9sm02237f

Cited by 29 publications

(23 citation statements)

References 86 publications

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“…Compared to nematic networks, smectic networks show larger magnitudes of actuation. Traugutt et al [ 16 ] compared the influence of liquid-crystal orientation on the thermo-mechanical properties of the main chain LCEs, they found that the actuation performance, work capacity, dissipation, and elastic modulus of the LCEs are all dependent on the alignment state of the mesogenic unit during synthesis.…”

Section: Application Of Lces For Soft Robotsmentioning

confidence: 99%

“…Therefore, the LCE networks will contract along the LC direction and expand in the vertical direction with the order–disorder transition of mesogens, resulting in the macroscopic shape changes of the bulk LCEs [ 14 , 15 ]. Similar to small molecule liquid crystals, the phase transition of LCEs can be achieved by environmental stimuli, such as temperature [ 16 , 17 ], humidity [ 18 , 19 ], organic solvent [ 20 , 21 ], electric [ 22 , 23 , 24 , 25 , 26 , 27 ], and ion [ 28 ] or remote stimuli, such as light [ 29 ], magnetic field [ 30 , 31 , 32 ], etc. Furthermore, the shape change of LCEs is fully reversible since their phase transition is dictated by thermodynamic equilibrium [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

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Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges

et al. 2021

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Liquid crystalline elastomers (LCEs) are lightly crosslinked polymers that combine liquid crystalline order and rubber elasticity. Owing to their unique anisotropic behavior and reversible shape responses to external stimulation (temperature, light, etc.), LCEs have emerged as preferred candidates for actuators, artificial muscles, sensors, smart robots, or other intelligent devices. Herein, we discuss the basic action, control mechanisms, phase transitions, and the structure–property correlation of LCEs; this review provides a comprehensive overview of LCEs for applications in actuators and other smart devices. Furthermore, the synthesis and processing of liquid crystal elastomer are briefly discussed, and the current challenges and future opportunities are prospected. With all recent progress pertaining to material design, sophisticated manipulation, and advanced applications presented, a vision for the application of LCEs in the next generation smart robots or automatic action systems is outlined.

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Section: Application Of Lces For Soft Robotsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges

et al. 2021

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“…In the example highlighted here, Lee and co‐workers fabricated thermoresponsive, 3D shape‐morphing LCEs in the macroscale as well as microscale. [ 116 ] The aza‐Michael addition‐based step growth polymerization used here was developed by the White group in 2015. [ 117,118 ] First, a commercially available LC monomer underwent chain extension with n‐butylamine, which resulted in a diacrylate‐functionalized poly(β‐amino ester)‐type LC oligomer.…”

Section: Synthetic Techniquesmentioning

confidence: 99%

Polymer Chemistry for Haptics, Soft Robotics, and Human–Machine Interfaces

Schara

Blau

Church

et al. 2021

Adv Funct Materials

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Progress in the field of soft devices—that is, the types of haptic, robotic, and human‐machine interfaces (HRHMIs) in which elastomers play a key role—has its basis in the science of polymeric materials and chemical synthesis. However, in examining the literature, it is found that most developments have been enabled by off‐the‐shelf materials used either alone or as components of physical blends and composites. A greater awareness of the methods of synthetic chemistry will accelerate the capabilities of HRHMIs. Conversely, an awareness of the applications sought by engineers working in this area may spark the development of new molecular designs and synthetic methodologies by chemists. Several applications of active, stimuli‐responsive polymers, which have demonstrated or shown potential use in HRHMIs are highlighted. These materials share the fact that they are products of state‐of‐the‐art synthetic techniques. The progress report is thus organized by the chemistry by which the materials are synthesized, including controlled radical polymerization, metal‐mediated cross‐coupling polymerization, ring‐opening polymerization, various strategies for crosslinking, and hybrid approaches. These methods can afford polymers with multiple properties (i.e., conductivity, stimuli‐responsiveness, self‐healing, and degradable abilities, biocompatibility, adhesiveness, and mechanical robustness) that are of great interest to scientists and engineers concerned with soft devices for human interaction.

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“…LCEs are more deformable and have more versatile processing conditions than LCNs; therefore, they can be fabricated into various geometries, including 0D particles, [23] 1D fibers, [24] 2D films, [25] and complex 3D shapes. [26] Therefore, the development of a new class of humidity-responsive actuators based on LCEs is highly desirable to overcome the aforementioned challenges associated with LCNs.…”

Section: Introductionmentioning

confidence: 99%

4D Printing of Hygroscopic Liquid Crystal Elastomer Actuators

Kim

Guo

Bae

et al. 2021

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100

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Liquid crystal elastomers (LCEs) are broadly recognized as programmable actuating materials that are responsive to external stimuli, typically heat or light. Yet, soft LCEs that respond to changes in environmental humidity are not reported, except a few examples based on rigid liquid crystal networks with limited processing. Herein, a new class of highly deformable hygroscopic LCE actuators that can be prepared by versatile processing methods, including surface alignment as well as 3D printing is presented. The dimethylamino‐functionalized LCE is prepared by the aza‐Michael addition reaction between a reactive LC monomer and N,N′‐dimethylethylenediamine as a chain extender, followed by photopolymerization. The humidity‐responsive properties are introduced by activating one of the LCE surfaces with an acidic solution, which generates cations on the surface and provides asymmetric hydrophilicity to the LCE. The resulting humidity‐responsive LCE undergoes programmed and reversible hygroscopic actuation, and its shape transformation can be directed by the cut angle with respect to a nematic director or by localizing activation regions in the LCE. Most importantly, various hygroscopic LCE actuators, including (porous) bilayers, a flower, a concentric square array, and a soft gripper, are successfully fabricated by using LC inks in UV‐assisted direct‐ink‐writing‐based 3D printing.

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Mechanically programmed 2D and 3D liquid crystal elastomers at macro- and microscale via two-step photocrosslinking

Abstract: A facile method for fabricating 3D-shaped liquid crystal elastomers at the macro- and microscales was developed by mechanical programming coupled with two-step photocrosslinking.

Cited by 29 publications

References 86 publications

Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges

Toward Application of Liquid Crystalline Elastomer for Smart Robotics: State of the Art and Challenges

Polymer Chemistry for Haptics, Soft Robotics, and Human–Machine Interfaces

4D Printing of Hygroscopic Liquid Crystal Elastomer Actuators

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