报告题目：Flexoelectric Effect in Liquid Crystals and Its Applications（液晶的挠曲电效应及其应用）

报告人：Prof. Deng-Ke Yang （杨登科） 肯特州立大学液晶研究中心及化学物理系终身教授

邀请人：黄明俊

报告时间：2022年5月20日（周五）上午9:30

线下报告地点：五山校区北区科技园2号楼324报告厅

线上腾讯会议：777-261-318 

欢迎广大师生踊跃参加！ 

前沿软物质学院

华南软物质科学与技术高等研究院

2022年5月18日

报告摘要：

　　由棒状分子组成的向列型液晶是一种介电介质，一般处于均匀取向状态，不表现出自发电极化。它们可以在介电相互作用下通过外部施加电压重新定向，并且对电压的极性不敏感。然而，具有特殊分子形状的向列型液晶在某些限域下表现出自发极化，这种现象称为挠曲电效应。在挠曲电相互作用下液晶分子会被外加电压重新定向，同时对电压的极性敏感。挠曲电效应可用于开发许多在介电相互作用下不可能实现的器件。本报告将讨论挠曲电效应的机制，讨论它在可重构光栅、波导显示和双模式智能窗户中的应用。例如，可以通过改变施加的电压来调整光栅的衍射角和强度；波导显示器可以显示图像并且被看穿，适用于增强显示；智能窗户可同时控制隐私和辐射能量。

　　Nematic liquid crystals, consisting of elongated molecules, in uniformly oriented state do not exhibit spontaneous electric polarization and are dielectric media. They can be reoriented by externally applied voltage under dielectric interaction and are not sensitive to the polarity of the voltage. Nematic liquid crystals of specially shaped molecules in special confinements or configurations exhibit, however, spontaneous polarization, a phenomenon known as flexoelectricity. They can also be reoriented by applied voltage under flexoelectric interaction and is sensitive to the polarity of the voltage. The flexoelectric effect can be made use to develop many devices, which are impossible under dielectric interaction. I will discuss the mechanism of flexoelectric effect. I will also discuss its applications in reconfigurable optical grating, waveguide display and dual mode switchable window. The diffraction angle and intensity of the grating can be adjusted by varying applied voltage. The waveguide display can display images and can be seen through, and is suitable for augmented display. The switchable window can control both privacy and radiant energy flow.

报告人简介：

　　杨登科（Yang Deng-Ke）教授于1984年在清华大学获得物理学学士学位，随后在夏威夷大学从事蓝相液晶的研究，并于1989年获得物理学博士学位，此后在肯特州立大学液晶研究中心开展液晶领域的研究工作并任职，目前是液晶研究中心及化学物理系的终身教授。杨登科教授的主要研究方向为胆甾相液晶、液晶/聚合物复合材料及电光器件，是世界著名的液晶物理与器件方面的科学家，是高分子稳定液晶材料和双稳态液晶显示材料与器件的奠基者之一。杨登科教授已从事液晶科学与应用的研究近30年，是本领域内公认的具有影响力的学者，同时也是液晶显示相关企业所熟知的科学家，在国内外具有非常高的知名度。已发表学术论文190余篇，申请专利23项，著有专著3本，参与编写章节的专著5本，近十年独立申请项目近20项，与多家业内知名企业开展合作。参加 APS、SID和ILC等协会，并积极参与国际会议、国际交流等。2005年因其在聚合物稳定器件与反射型液晶显示领域的开创性工作获得SID的特殊贡献奖 ( Information Display Society Special Recognition Award )，2007年因其在双稳态、反射型胆甾相液晶显示、聚合物稳定液晶器件方面的科学与技术贡献及其对液晶科学和技术领域的教育所做出的突出贡献被聘为SID Fellow；其指导的学生论文也多次在重要的国际会议上获奖。他在 2017 年获得了 SID 的 Slottow-Owaki 奖，以表彰他对液晶显示领域学生教育和培训的杰出贡献。他还于 2017 年获得肯特州立大学年度杰出研究和奖学金。他被斯坦福大学评为世界前 2% 的科学家之一。

　　Deng-Ke Yang is a professor in the department of physics and the materials science program in advanced materials and Liquid Crystal Institute at Kent State University. He received his B.S. in physics from Tsinghua University in China in 1984 and his Ph.D. in physics from the University of Hawaii in 1989.  He joined Kent State University in 1989. His main research interest is in liquid-crystal physics and devices. He has coauthored three books and 10 book chapters. He also has published more than 200 papers in refereed journals and SID proceedings. He holds more than 30 patents. He received the Society for Information Display’s Special Recognition Award in 2005 for his pioneering work on polymer-stabilized cholesteric devices and reflective displays. He was elected a fellow of the SID in 2007 for his significant scientific and technological contributions to bistable, reflective cholesteric displays and to polymer-stabilized cholesteric devices, and for his outstanding contributions to education in the field of liquid-crystal technology. He received SID’s Slottow-Owaki Prize in 2017 for his outstanding contributions to the education and training of students and professionals in the field of liquid-crystal displays. He also received Kent State University’s annual Outstanding Research and Scholarship Award in 2017. He has been named one of the world’s top 2% of scientists by Stanford University.