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Three different types of polyols-poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and poly(tetramethylene glycol)-with different molecular weights ( Mn) were incorporated into the prepolymer structure, and the effects were examined with regard to the morphology and performance of holographic polymer dispersed liquid crystal. Among them, PEG showing the lowest glass transition temperature ( Tg) exhibited the lowest threshold voltage ( Vth), lowest operating voltage ( Vop), and lowest diffraction efficiency with slow grating formation owing to its high viscosity of prepolymer mixture. The Tg decreased with increasing Mn because of the decreased crosslink density and hydrogen bonding, which reduced the anchoring strength, Vth and Vop. PPG400 gave Vth and Vop of approximately 7 and 24 V, respectively, with a contrast ratio of approximately 12. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

Cholesteric liquid crystal elastomers (CLCEs) are unique anisotropic rubbers that can change their structural color in response to various stimuli such as heat, chemicals, electric fields, and mechanical stress. Methods such as anisotropic deswelling and surface alignment have been adopted to prepare CLCEs; however, they have limitations in creating spatially controlled CLCE geometries. In this work, a direct ink writing (DIW)‐based 3D‐printable CLCE that can be prepared by extruding viscous CLC ink is developed through a 3D printer nozzle, followed by photopolymerization. Interestingly, the helical axis is inclined to the printing direction by ≈32° due to a combination of the shear‐induced alignment causes during extrusion and the elongational force generated during deposition onto the substrate. This unusual helical axis distortion leads to both blue and red shifts of the reflection color depending on the direction of observation relative to the printing axis. Notably, the printed CLCE exhibits anisotropic mechanochromism upon stretching, because of the stretching‐direction‐dependent variations in the slant angle of the helical axis. This anisotropic mechanochromism can be harnessed to develop a unique CLCE‐based strain sensor displaying intricate color patterns upon stretching, with significant application potential in encryption, anticounterfeiting, and structural health monitoring. [ABSTRACT FROM AUTHOR]

In an article published in Advanced Functional Materials, Suk‐kyun Ahn and their colleagues discuss the creation of cholesteric liquid crystal elastomers (CLCEs) with slanted helices using direct ink writing. The researchers observed an anisotropic mechanochromic response in the printed CLCEs when they were stretched in relation to the printing direction. This unique property allows for the development of strain sensors that display intricate and programmable color patterns when stretched. The study was conducted by Jihye Choi, Yeongyu Choi, Jin‐Hyeong Lee, Min Chan Kim, Sungmin Park, Kyu Hyun, Kyung Min Lee, Tae‐Hoon Yoon, and Suk‐kyun Ahn. [Extracted from the article]

We propose a single-layered electrode structure using three voltage levels instead of two to achieve high transmittance in an in-plane switching liquid crystal display device. The proposed structure consists of two pixel electrodes and one common electrode. By using three voltage levels, we can generate an in-plane electric field higher than that in a conventional in-plane switching device. We confirmed that by using the proposed structure, the transmittance of a liquid crystal device can be increased from 29% to 35% at a slightly lower operating voltage without using the double-layered electrode structure required for the fringe-field switching mode. The transmittance of the proposed device is higher than that of the fringe-field switching device. [ABSTRACT FROM AUTHOR]

Chiral photonics has emerged as a key technology for future optoelectronics, such as quantum information and encryption, by making use of photonic waves from enantiomeric structures. An inevitable challenge for realizing such chiral optoelectronics is the development of near‐infrared circularly polarized (NIR CP) light‐sensing photodetectors that convert optical power and circular polarization direction into distinguishable electrical signals. Herein, a simple and promising strategy for high‐performance NIR CP light‐sensing organic phototransistors (NIR CPL‐OPTRs) applicable to highly secure optoelectronic encryption is proposed. By directly assembling a standalone cholesteric liquid‐crystal network film in a thin‐film NIR CPL‐OPTR, remarkable responsivity and distinguishability are achieved. The synergetic effect of amplification of the photocurrent signal by the applied electric field and improved light absorption by the reduced reflection in the multilayered structure leads to high responsivity. As a proof‐of‐concept, the chiral phototransistor arrays are demonstrated as a physically unclonable function device and exhibit enhanced cryptographic characteristics. [ABSTRACT FROM AUTHOR]