Microfluidic synthesis of micrometer-sized photoresponsive actuators based on liquid crystalline elastomers
Microfluidic synthesis of micrometer-sized photoresponsive actuators based on liquid crystalline elastomers
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DOI：
10.1039/c6tc02587k
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发表时间：
2016-09
影响因子：
6.4
通讯作者：
Lukas Braun;Tristan Hessberger;R. Zentel
中科院分区：
文献类型：
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作者：
Lukas Braun;Tristan Hessberger;R. Zentel
本文首次报道了微米级光敏液晶弹性体(LCE)的制备。使用微流控装置，通过连续的“在飞”技术制备LCE颗粒，可以在不到2秒的照射时间内快速处理这些颗粒。为了加速聚合反应，并使制备几百微米厚的样品成为可能，我们通过添加漂白剂对近红外光引发体系进行了改进。除了光引发剂外，还使用了含有偶氮基和液晶交联剂的侧链液晶单体。为了优化聚合参数，首先制备了LCE薄膜。这些薄膜在向列相-各向同性相变时表现出超过40%的强烈热响应驱动，并且由于偶氮基的反顺异构化，在光照射仅8秒时，其长度改变了34%。研究了制备的颗粒对加热、光照射和在良好溶剂中溶胀的响应。对于这些粒子，发现了约24%的强烈光响应驱动，这可以通过红光照射(8分钟)或在黑暗中通过偶氮基的等温反向异构化(17分钟)而可逆。我们的粒子的光诱导驱动的可逆性使它们成为微型机器人中作为人造肌肉应用的有希望的候选者。
The fabrication of photoresponsive micrometer-sized liquid crystalline elastomer (LCE) particles has been described in this article for the first time. The preparation of the LCE particles using a microfluidic device by a continuous “on the fly” technique allows their fast processing with an irradiation time of less than 2 seconds. In order to accelerate the polymerization and to make the preparation of samples with thicknesses of several hundred microns possible, we modified a NIR-photoinitiation system by adding a bleaching agent. In addition to the photoinitiator, a side-chain liquid crystalline monomer containing an azo-group and a LC-crosslinker were used in the polymerization mixture. For the optimization of the polymerization parameters, LCE films were produced first. These films showed a strong thermoresponsive actuation of more than 40% upon the nematic–isotropic phase transition and changed their length by up to 34% during irradiation with light for just 8 seconds, due to the trans–cis isomerization of the azo-group. Fabricated particles were investigated with respect to their response to heating, irradiation with light and swelling in a good solvent. A strong photoresponsive actuation of about 24% was found for these particles, which was reversible either by irradiation with red light (8 minutes) or by an isothermal back-isomerization of the azo-group in the dark (17 minutes). The reversibility of the light induced actuation of our particles makes them promising candidates for application as artificial muscles in microrobotics.