Switching in a Biaxial Smectic A - like Phase

• Published in: Liquid crystals today Vol. 30; no. 2; pp. 20 - 25
• Main Authors: Panarin, Yuri P., Tschierske, Carsten, Vij, Jagdish K.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 03.04.2021; Taylor & Francis Ltd
• Subjects: Alignment; Antiferroelectricity; Biaxial Nematic; Biaxial Smectic A (SmA; Coupling (molecular); Crystal structure; Crystallinity; Crystals; Electric fields; Liquid crystals; Nematic crystals; Refractivity; Switching; Switching in bent-core liquid crystalline systems
• ISSN: 1358-314X; 1464-5181
• DOI: 10.1080/1358314X.2021.1991695

Comments and the work presented in this paper aim at initiating discussion within the liquid crystalline community about the nature of different biaxial phases and their switching mechanisms. The mechanisms have the potential for applications in switching devices for displays and photonics. Claire Meyer et. al. interestingly report recently a fast Freedericksz-like transition of the secondary director in the biaxial Smectic A b phase of a mixture of two compounds. Fast switching in liquid crystals occurs through a coupling of the biaxiality with the electric field. To realise this potential, one of the major goals of the liquid crystal community had been to discover biaxial nematic liquid crystals. In a biaxial liquid crystalline phase, the refractive indices along the three orthogonal axes are all different [n 11 ≠ n 22 ≠ n 33 ] as opposed to these being different only along the two orthogonal directions n 11 ≠ n 22  = n 33 in uniaxial nematics. In this notation 1, 2 and 3 are the three orthogonal axes that coincide with the major and the two minor directors. The biaxial nematic phase has been elusive for over half a Century. It has therefore proven to be almost impossible to meet the goal of achieving fast switching using biaxial nematics. Ferroelectric and antiferroelectric liquid crystals were discovered in 1975 and 1989 by R. Meyer in the USA and Atsuo Fukuda in Japan, respectively, for fast switching. These have been used in devices for niche but limited high-resolution applications as the devices using these liquid crystals suffered not only from achieving proper alignment at surfaces but also showed poor recovery of alignment following repeated cycles of switching.