液晶彈性體(liquid crystal elastomers, LCEs)為聚合液晶物網絡(liquid crystal networks, LCNs)的一種，其形狀可以通過光或熱等刺激產生靈活改變。液晶彈性體優越的形狀變化能力在發展人造肌肉、微型機器人，以及軟式電子產品等領域具有巨大的應用潛力。近幾年3D列印技術的迅速發展與普及，使得結合液晶彈性體與3D列印技術這件事成為可能，進而衍生出新型的4D列印技術，也就是讓列印出的三維液晶彈性體結構隨著受刺激的時間產生整體形狀變化。由於液晶彈性體的變形方式與聚合物網絡中液晶分子的配向方向有顯著相關，因此了解液晶彈性體中液晶分子在列印過程中的排列狀況，並進一步加以控制，對於3D列印液晶彈性體來說就顯得特別重要。先前的文獻曾報導，可利用列印的噴頭所提供的拉力在彈性體內部產生剪切應力來排列液晶分子，排列方向將平行於列印噴頭的移動方向。


在本論文中，我們設計並構建了一台專用於列印液晶彈性體的自製3D列印機，測試了兩種文獻常見的液晶彈性體配方，並討論了不同列印參數對所印出之液晶彈性體配向整齊度的影響，所探討的因素包括噴頭和基板之間的距離、噴頭溫度、列印速度，以及光聚合條件。通過調整上述因素，成功列印出了具有不同配向整齊程度和紋理的液晶彈性體，並從中找出最適合用於3D列印液晶彈性體的參數，優化了製程的良率。此外也可利用不同的列印參數來設計液晶彈性體的整體形變程度與方向，拓寬設計空間並推動4D列印的發展。期盼本論文可以提供列印液晶彈性體相關研究做為製程調整上的參考，並且有助於軟機器人和柔性電子產品的研發與製造。

Liquid crystal elastomers (LCEs) are polymeric liquid crystal networks whose shape can be flexibly changed by stimuli such as light or heat. The superior shape-changing capability of LCEs has great potential in the development of artificial muscles, micro-robots, and soft electronics. With the rapid development and popularization of 3D printing technology in recent years, the combination of LCEs and 3D printing technology can be realized and results in a new type of printing technology, 4D printing, which allows the printed 3D structure based on LCEs to change its shape with the stimulation time. Since the deformation of LCEs is significantly related to the orientational direction of the liquid crystal mesogens within the polymer networks, it is important to realize how the mesogens are aligned during the printing process of the elastomers and to further propose a method for the control of the mesogens orientations within the LCEs during the printing process. According to the previous literature, the pulling force provided by the nozzle can induce shear stress inside the elastomer to align the liquid crystal mesogens, and the alignment direction will be parallel to the moving direction of the nozzle.


In this thesis, we demonstrate a home-made 3D printer designed for printing LCEs and test two LCE recipes commonly reported in related works. Moreover, the influence of various factors, including the distance between nozzle and substrate, nozzle temperature, printing speed, and photopolymerization conditions, on the orientation of the printed LCEs are discussed. By adjusting the above factors, LCEs with various degrees of homogeneous alignment and textures can be obtained. The optimal parameters for 3D printing LCEs can be further found out to improve the yield. In addition, by adopting different printing parameters, the overall deformation degree and direction of the LCEs can be controlled, which is expected to broaden the design possibility and promotes the development of 4D printing. We expect that this work can be a reference or guide for researches or adjustment for the fabrication process of printing LCEs and helpful for the development and manufacture of soft robots and flexible electronic products.

致謝 I
摘要 III
Abstract IV
目錄 VI
圖目錄 VIII
第一章 緒論 1
1.1 前言 1
1.2 研究背景 2
1.3 研究動機 3
第二章 原理 5
2.1 液晶基本介紹 5
2.1.1 液晶介紹 5
2.1.2 液晶的相態與結構 7
2.1.3 液晶的光學異向性 13
2.1.4 液晶的介電異向性 14
2.1.5 連續彈性體形變理論 15
2.2 液晶聚合物簡介 16
2.2.1 液晶聚合物分子結構 16
2.2.2 液晶聚合物之熱機械響應原理 19
2.2.3 液晶聚合物之光機械響應原理 21
第三章 3D列印液晶彈性體 25
3.1 3D列印技術 25
3.1.1 主流3D列印技術簡介 25
3.2 3D列印液晶彈性體與其配向原理 31
3.2.1 形狀記憶高分子(Shape memory polymers, SMPS) 32
3.2.2 黏彈性(Viscoelasticity) 38
3.2.3 剪切作用與噴頭配向原理 43
第四章 實驗架構與材料製備 47
4.1 自製三維液晶彈性體列印設備架設 47
4.1.1 溫控設備選擇 49
4.2 液晶彈性體材料混合物製備 54
4.2.1 材料介紹 54
4.2.2 製備方式 56
第五章 結果與討論 57
5.1 RM105+257墨水列印討論 57
5.1.1 溫度對列印RM105+257墨水的影響 57
5.1.2 聚合光強度對列印RM105+257墨水的影響 66
5.1.3 列印線寬與材料的缺陷 68
5.2 RM82墨水列印討論 73
5.2.1 噴頭溫度對配向效果之影響 73
5.2.2 噴頭移動速度對配向效果之影響 85
5.2.3 噴頭高度對配向效果之影響 88
5.2.4 噴頭移動速度與線寬之關係 89
第六章 結論與未來展望 95
6.1 結論 95
6.2 未來展望 96
參考文獻 98

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