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Angew. Chem., Tsinghua University's Associate Professor Ji Yan Group: Thermo-editability of "switchable" LCD elastomer drivers
2020-01-08 Source: Polymer Technology
Keywords: LCD elastomer driver

The rapid development of smart devices in various emerging and mature fields (such as energy, aerospace and biomedicine) has created an urgent need for high-performance soft actuators. Among them, the software driver with thermal reprogrammability can not only flexibly change the structure or driving mode without being limited by its shape, but also is expected to be used to build a new generation of adaptive equipment with high accuracy and excellent deformation ability. . However, this seemingly fascinating performance often comes at the expense of performance stability, such as drive stability and dimensional stability. The fatal contradiction between thermal reeditability and drive performance stability has prevented further development of high-performance thermally adaptable software drives.

Recently, Associate Professor Ji Yan and his research team at Tsinghua University , inspired by circuit control, think that if the thermal reeditable performance is as flexible as a circuit, it can be “switched on”, that is, when it is necessary to edit the shape and function (ON) And when the drive is working and storing, it can be completely turned off (OFF), then the above contradictions can be solved. They used a quenchable dynamic exchange reaction of silicon and oxygen, and used the "swell after synthesis" processing method to achieve the thermal reeditability of repeatedly "switching" liquid crystal elastomer (LCEs) drivers (Figure 1, Figure 2). .

Figure 1 (a) Schematic diagram of thermal reeditability of a controllable "switch" liquid crystal elastomer driver; (b) Anion-regulated dynamic silicon-oxygen exchange reaction.

This "swelling after synthesis" treatment method does not require a complex dynamic network design to activate the dynamic exchange reaction of silicon and oxygen in a very commonly used classic silicone liquid crystal elastomer to achieve editable preparation from originally inert materials. Three-dimensional complex driver; and the dynamic network can be deactivated by heating, that is, thermal reeditability is turned off, and the drive's drive, size, and performance stability are well guaranteed (Figure 2, Figure 3).

Figure 2 (a) Chemical structure of a silicon-oxygen liquid crystal elastomer; (b) Preparation of a stable single-domain liquid crystal elastomer driver through a switching strategy; (c) Thermal drive cycle test.

Figure 3 Starting from ordinary silicone liquid crystal elastomer through the "switch" strategy to prepare a three-dimensional driver

下高温环境中放置超过72小时,材料的驱动性能也能保持不变。 The driving performance of the material remains unchanged even after being left in a high-temperature environment at 180 C for more than 72 hours. Through the iteration of the above methods, this type of drive can be repeatedly edited, reused and reused with excellent stability (Figure 4). In addition, with black ink for partial patterning, thermal reeditability can also be partially turned off, enabling seamless integration of completely different drive modes into one actuator to perform more sophisticated and complex tasks (Figure 5 ).

Figure 4 Editing and recycling of stable drives again

Figure 5 (a) Schematic diagram of selectively turning off thermal reeditability; (b) thermal drive of a hook drive, reversible telescopic drive on the upper part and reversible bending drive on the lower part; (c) light drive of the hook drive, The lower part drives the light response.

This switching strategy is universal and easy to operate, and can be used in many silicone polymer networks. Therefore, many previously known materials with unique and good properties can be modified by the above methods to prepare more A variety of thermally adaptable devices with stable performance will greatly promote the innovation and application of flexible drivers, liquid crystal elastomers and silicone materials.

The results were published in Angew. Chem. Int. Ed., DOI: 10.1002 / anie.201915694. The first author of the article was Dr. Yahe Wu , Department of Chemistry, Tsinghua University , and the corresponding author was Associate Professor Ji Yan, Tsinghua University. Professor Wei Yan, Dr. Yang Yang, Dr. Chen Qiaomei, and Dr. Qian Xiaojie from Tsinghua University participated in the research.

Paper link:

Liquid crystalline soft actuators with switchable thermal reprogrammability,

http://onlinelibrary.wiley.com/doi/10.1002/anie.201915694

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