Dynamic Liquid Crystalline Networks for Twisted Fiber and Spring Actuators Capable of Fast Light-Driven Movement with Enhanced Environment Adaptability

Jiang, Zhi‐Chao; Xiao, Yao‐Yu; Cheng, Ruidong; Hou, Junbo; Zhao, Yue

doi:10.1021/acs.chemmater.1c02073

Cited by 54 publications

(60 citation statements)

References 51 publications

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“…[50,51] In addition, fiber coiling can be achieved to provide diverse deformation modes in place of simple rotational motion if the fiber is prevented from rotating during actuation. The responsiveness of LCE to various stimuli such as, light, [52][53][54][55][56] heat, [57,58] electricity, [59][60][61] magnetic fields, [62] and solvents, [63] can be exploited to increase the functional versatility and performance of LCETFs for applications in energy harvesters, [64] artificial muscles, [46] and soft robots. [65,66] Adv.…”

Section: Discussionmentioning

confidence: 99%

Liquid Crystal Elastomer Twist Fibers toward Rotating Microengines

et al. 2022

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too small, the fibers will untwist before use; an excessive anchoring force will, on the other hand, prevent the fibers from moving and responding to external stimuli. [5][6][7][8] Therefore, the development of twist fibers in an untethered form will avoid the need for anchoring, simplify experimental design, and make various operations feasible. In practical applications, reversible rotational actuation is also important for twist fibers because it allows the fibers to respond to external stimuli repeatedly without the need to insert twists into the fibers each time before use. [9][10][11] In addition, high torque and rotational deformation are key factors in the operation of rotating microengines. The torque produced by the twist fibers must be sufficiently large to rotate objects. A large rotational deformation of the twist fibers is desirable for moving objects over a large distance in a wide range of applications. [12,13] So far, various materials have been utilized for untethered twist fibers that exhibit reversible rotational deformation upon stimuli. The actuation performance of these materials varies with the material. For example, twist fibers made from carbon materials or polymers can generate large rotational deformation of 588° mm −1 , but the generated specific torque reaches only 0.63 N m kg −1 . [9,10] To date, the construction of untethered twist fibers with reversible responsiveness, high torque, and large rotational deformation remains a challenge. A possible solution is the development of a material with high intrinsic deformation ratio and reversible responsiveness for fabricating twist fibers. [14] Among the various stimuli-responsive materials, liquid crystal elastomers (LCEs) have attracted increasing attention because of their dramatic and reversible stimuli-responsive deformation. [15][16][17][18][19][20][21][22][23] LCEs exhibit the two properties of high intrinsic deformation ratio and reliable reversibility which originate from the change in mesogenic alignment upon external stimuli. [24] These properties are important for improving the rotational performance of twist fibers. Here, we develop a template method based on a two-step cross-linking strategy to fabricate liquid crystal elastomer twist fibers (LCETFs). These untethered LCETFs can reversibly generate high torque and large rotational deformation. Fibers made from LCE have been widely exploited as actuators, [25][26][27][28] artificial muscles, [29][30][31][32] and soft robots. [33,34] In this work, we insert twists into LCE fibers Untethered twist fibers do not require end-anchoring structures to hold their twist orientation and offer simple designs and convenient operation. The reversible responsiveness of these fibers allows them to generate torque and rotational deformation continuously upon the application of external stimuli. The fibers therefore have potential in rotating microengines. In practical applications, high torque and rotational deformation are desirable to meet work capacity requirements. However, the simultan...

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Section: Discussionmentioning

confidence: 99%

Liquid Crystal Elastomer Twist Fibers toward Rotating Microengines

et al. 2022

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Section: Liquid Crystal Elastomers With Dynamic Covalent Bondsmentioning

confidence: 99%

“…The first example of incorporating dynamic bonds into LCE was demonstrated by Ji and coworkers in 2014. [241] Since then, a variety of dynamic chemistry has been introduced into LCEs, such as, transesterification, [58,59,149,241,242] addition−fragmentation chain transfer reaction, [243][244][245][246] Diels-Alder reaction, [247][248][249] and disulfide bond. [250][251][252] These dynamic systems can be activated by heat or light to decrosslink the LCE network, allowing the manipulation of molecular orientation and the fabrication of macroscopic LCE shape.…”

Section: Liquid Crystal Elastomers With Dynamic Covalent Bondsmentioning

confidence: 99%

“…Furthermore, due to the facile processing and the stable of orientation states, carbon nanotube composite based on this DA bond containing LCE has been fabricated by the same group, achieving hierarchically twisted geometries and their fast light-driven movement with the addition of carbon nanotube. [248] Cai et al reported a new LCE based on the "living" exchange reaction of disulfide bonds, which occurs at room temperature. [264] The "living" exchange reaction relies on the significantly extended lifetime of free radicals that are generated during the cleavage of the disulfide bond at high temperature (Figure 25a).…”

Section: Modulation Of Alignmentmentioning

confidence: 99%

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Progress in Utilizing Dynamic Bonds to Fabricate Structurally Adaptive Self‐Healing, Shape Memory, and Liquid Crystal Polymers

Zhang

Wang

et al. 2022

Macromol. Rapid Commun.

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Stimuli‐responsive structurally dynamic polymers are capable of mimicking the biological systems to adapt themselves to the surrounding environmental changes and subsequently exhibiting a wide range of responses ranging from self‐healing to complex shape‐morphing. Dynamic self‐healing polymers (SHPs), shape‐memory polymers (SMPs), and liquid crystal elastomers (LCEs), which are three representative examples of stimuli‐responsive structurally dynamic polymers, have been attracting broad and growing interest in recent years because of their potential applications in the fields of electronic skin, sensors, soft robots, artificial muscles, and so on. Recent advances and challenges in the developments toward dynamic SHPs, SMPs, and LCEs are reviewed, focusing on the chemistry strategies and the dynamic reaction mechanisms that enhance the performances of the materials including self‐healing, reprocessing, and reprogramming. The different dynamic chemistries and their mechanisms on the enhanced functions of the materials are compared and discussed, where three summary tables are presented: A library of dynamic bonds and the resulting characteristics of the materials. Finally, a critical outline of the unresolved issues and future perspectives on the emerging developments is provided.

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“…Active Janus beads were recently assembled to flexible chains in an electric field [17], but so far only in staggered orientation with no sideways propulsion. Other examples are anisotropic rollers, for instance flexible fibers propelled by a flux of heat or swelling agent to roll along their long axis [18,19] as well as light-driven rolling helices and spring actuators [20].…”

Section: Introductionmentioning

confidence: 99%