壓電材料誘發聲波對膽固醇液晶結構之影響;Impact of piezoelectric-induced acoustic waves on cholesteric liquid crystal structure

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題名:	壓電材料誘發聲波對膽固醇液晶結構之影響;Impact of piezoelectric-induced acoustic waves on cholesteric liquid crystal structure
作者:	林芳慈;Lin, Fang-Tzu
貢獻者:	光電科學與工程學系
關鍵詞:	膽固醇液晶;聲波;cholesteric liquid crystal;acoustic waves
日期:	2023-11-22
上傳時間:	2024-09-19 15:53:45 (UTC+8)
出版者:	國立中央大學
摘要:	一般而言，控制液晶分子排列通常以電控、光控以及熱控為主，然而利用聲波改變液晶分子排列的研究並不多見，因此本論文的研究主要為利用聲波改變膽固醇液晶分子的排列，而聲波的來源為環形壓電陶瓷板的振動。在第一部分中，實驗過程皆將液晶盒控溫於60°C下進行，膽固醇液晶為向列型液晶(HTW106700-100)以及手性分子(R-5011)之混合，且玻璃基板為圓形並作水平配向處理，將環形壓電陶瓷板黏貼於液晶盒邊緣並施加特定頻率之正弦交流電訊號使其產生聲波傳遞至膽固醇液晶當中，此時膽固醇液晶排列受聲波產生擾動自焦錐態切換為非完美平面態，最終關閉聲波後，由實驗結果可說明聲波能促使膽固醇液晶在水平配向之液晶盒中流動並穩定在非完美平面態。此外，藉由記錄施加不同聲波強度形成非完美平面態的速率，發現聲波的強度與液晶排列的速率呈現正相關，且在聲波強度較強的情況下會有熱效應的產生；在生成非完美平面態的過程當中，另發現部分區域存在混亂之膽固醇液晶結構，此結構生成之原因將於第五章之非完美平面態穿透頻譜作詳細討論。在第二部分實驗當中，使用與第一部分相同之膽固醇液晶注入基板無配向處理之圓形液晶盒，且實驗條件同為在溫控盒60°C下進行，持續施加特定頻率的正弦交流電於環形壓電陶瓷板產生聲波於液晶盒後，起始焦錐態會切換為多個具有亮暗態分佈的圓形特殊結構，且此特殊結構隨時間的推移而變大且相互推擠，最終關閉聲波後依舊穩定於此態，而此特殊結構之穿透率高，研究中為探究其結構之排列方式，我們藉由穿透頻譜、摻雜二色性染料以及更改短螺距膽固醇液晶為長螺距之膽固醇液晶進行分析，並命名此圓形特殊結構為徑向螺紋結構(Radial lying helix)。 ;In general, many methods exist to change the arrangements of liquid crystal (LC) molecules, including optical, electrical, and thermal approaches. However, research on changing LC arrangements by acoustic waves is relatively rare. Therefore, the main purpose of this thesis is to modify the arrangements of cholesteric liquid crystal (CLC) molecules using acoustic waves. Moreover, the source of acoustic waves is generated by the vibrations of a piezoelectric ceramic ring. In the first part, all experiments were conducted in a temperature controller at 60°C. The CLCs are a mixture of nematic LCs (HTW106700-100) and chiral dopant (R-5011). Furthermore, the shape of the glass substrates is circular and the substrate is treated with horizontal alignment. To induce acoustic waves in the CLCs, a piezoelectric ceramic ring was attached to the LC cell′s edge, and a sinusoidal voltage with a specific frequency was applied. These acoustic waves disrupted the CLC alignment, leading to a transition from the focal conic textures to the imperfect planar textures. After turning off the acoustic waves, the experimental results indicated that acoustic waves could induce the flow of CLCs in the LC cell and stabilize it in the imperfect planar textures. Additionally, it was found that the intensity of the acoustic waves was positively correlated with the rate of LC rearrangement, and under high acoustic wave intensity, a thermal effect was observed. Furthermore, during the process of generating the imperfect planar textures, disordered CLC structures were observed in certain regions, which will be analyzed by transmission spectra of the imperfect planar textures. In the second part, the composition of CLCs was the same as in the first part, and the cell was treated without any alignment layer. The experimental conditions remained the same, conducted in a temperature controller at 60°C. When we keep applying a sinusoidal voltage with a specific frequency to the piezoelectric ring to generate acoustic waves transmitted into the LC cell, the initial focal conic textures can be switched to multiple circular structures with bright and dark distributions. The experimental results show that these unique structures grew larger and larger and compressed over time. To explore the arrangement of its structure, we conducted an analysis using transmission spectra, doped dichroic dye, and changing the short-pitch CLCs to long-pitch CLCs. Ultimately, we named this circular unique structure the "Radial Lying Helix" structure.
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