Speaker：Prof. Deng-Ke Yang ,Kent State University
Title: Flexoelectric Effect in Liquid Crystals and Its Applications
Invited by Prof. Mingjun Huang
Time：May 20, 2022 (Friday 9：30 am)
Venue: Lecture Room 324, AISMST (Building #2, KeJiYuan, North Campus)
Online：Tencent Conference 777-261-318
Faculties and students are warmly welcome.
Abstract:
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.
Brief Biography：
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.