| dc.description.abstract | 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. | en_US |