Title: Photocontrolled Liquid Transportation in Microtubes by Manipulating Mesogen Orientations in Liquid Crystal Polymers

Author: Quan Liu, Yuyun Liu, Jiu-an Lv, Erqiang Chen, Yanlei Yu*

Journal: Adv. Intell. Syst., 2019, 1(6), 1900060

Abstract:

Tubular microactuators (TMAs) fabricated by photodeformable liquid crystal polymers (LCPs) pave a significant way for smart microfluidic applications with contactless, spatial, and precise manipulation of liquids. To realize liquid transportation in these TMAs, LCPs should have excellent photodeformation property and suitable mechanical properties. Herein, linear liquid crystal polymers (LLCPs) with different mesogen orientations are used to prepare TMAs to study their liquid transportation behaviors. The mesogen orientation in each LLCP is formed spontaneously and varies with the spacer length, leading to different deformations of LLCP films. It is found that only LLCPs with mesogens oriented out-of-plane realize self-support of the TMAs, whereas the TMAs with mesogens oriented in-plane are so weak that they collapse in the radial direction, indicating the importance of mesogen orientation in fabricating three-dimensional structures. Upon attenuated 470 nm light irradiation, the TMAs deform to an asymmetric conical structure, leading to the motion of liquid slug toward the narrow side. The liquid motion is accelerated in the TMA with longer spacer, showing the control of liquid speed by the mesogen orientation. These photocontrolled TMAs are expected to be applied in biological applications, such as whole blood analysis and flow cytometry, for precise liquid manipulation.

论文链接：https://onlinelibrary.wiley.com/doi/pdf/10.1002/aisy.201900060

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本文通过开环易位聚合（ROMP）合成了三种不同间隔基长度的偶氮苯光致形变液晶聚合物（LLCP），分别是PC-AB6，PC3AB6，PC7AB6。其中PC-AB6的液晶基元自发形成面内取向，PC3AB6和PC7AB6的液晶基元为面外取向。由于平行于液晶基元取向方向的LLCP微管状执行器（TMA）的杨氏模量大约是垂直方向的两倍。因此，紫外光照射时，PC-AB6 TMA在径向上会塌陷，而PCnAB6 TMAs具有良好的自支撑性，表明了LCP中的平面外取向对于在制造3D管状结构时提供足够的机械强度至关重要。