https://orbilu.uni.lu/bitstream/10993/20503/1/Lagerwall%20%26%20Scalia%202012.pdf

A new era for liquid crystal research: Applications of liquid crystals in soft matter nano-, bio- and microtechnology

The sensitive response of the nematic graphene oxide (GO) phase to external stimuli makes this phase attractive for extending the applicability of GO and reduced GO to solution processes and electro-optic devices. However, contrary to expectations, the alignment of nematic GO has been difficult to control through the application of electric fields or surface treatments. Here, we show that when interflake interactions are sufficiently weak, both the degree of microscopic ordering and the direction of macroscopic alignment of GO liquid crystals (LCs) can be readily controlled by applying low electric fields. We also show that the large polarizability anisotropy of GO and Onsager excluded-volume effect cooperatively give rise to Kerr coefficients that are about three orders of magnitude larger than the maximum value obtained so far in molecular LCs. The extremely large Kerr coefficient allowed us to fabricate electro-optic devices with macroscopic electrodes, as well as well-aligned, defect-free GO over wide areas.

Electro-optical switching of graphene oxide liquid crystals with an extremely large Kerr coefficient

Electric-field-induced birefringence of a polymer-stabilized blue-phase liquid crystal (BPLC) is investigated In the low field region, conventional Kerr effect holds As the electric field increases, the induced birefringence gradually saturates and deviates from Kerr effect An exponential convergence model, called extended Kerr effect, is proposed to fit the experimental data Good agreement between experiment and model is obtained This extended Kerr effect will make a significant impact to the optimization of emerging BPLC display devices

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Extended Kerr effect of polymer-stabilized blue-phase liquid crystals

A protrusion electrode structure is proposed to dramatically lower the operation voltage of the emerging blue-phase liquid crystal displays (BP-LCDs). Simulation results indicate that the generated horizontal electric field is not only strong but also penetrates deeply into the bulk LC layer. As a result, a low voltage (∼10 Vrms) and reasonably high transmittance (∼70%) BP-LCD can be achieved. This approach enables the BP-LCDs to be addressed by amorphous silicon thin-film transistors (TFTs). Widespread application of TFT BP-LCDs is foreseeable.

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Low voltage blue-phase liquid crystal displays

3D photonic nanostructures with desirable functionalities in the visible light region and beyond have been recently given vast and increasing attentions because of the ability to control or confine electromagnetic waves in all three dimensions. Although substantial progress has been made in fabricating 3D nanostructures by means of lithography and nanotechnology, various bottlenecks still need to be overcome, and developing soft 3D stimuli-directed nanostructures with tailored properties remains a challenging but exciting work. In this context, soft nanotechnology—i.e., exploiting self-organized soft materials in nanotechnology—is emerging as a vibrant and burgeoning field of research in the bottom-up nanofabrication of intelligent stimuli-driven 3D photonic materials and devices. Liquid-crystalline materials undoubtedly represent such a marvelous dynamic system that combines the liquid-like fluidity and crystal-like ordering from molecular to macroscopic material levels. Importantly, being “soft” makes the materials responsive to various stimuli such as temperature, light, mechanical force, and electric and magnetic fields as well as chemical and electrochemical reactions, resulting in a fascinating tunability of dynamic photonic bandgaps in the 3D nanostructure that provides numerous opportunities in all-optical integrated circuits and next-generation communication systems. Here, the development of 3D photonic nanostructures is reviewed, culminating with perspectives for the future scope and challenges of these emerging soft 3D photonic nanostructures towards device applications.

Stimuli-Directing Self-Organized 3D Liquid-Crystalline Nanostructures: From Materials Design to Photonic Applications

Polymer-stabilized optically isotropic liquid crystals, including blue phases, are emerging as a strong contender for next-generation display technology because they exhibit some revolutionary features such as no need for surface alignment, submillisecond response time, isotropic dark state, and cell gap insensitivity. The basic material properties, including electric field-induced birefringence, dispersion relation of Kerr constant, and temperature dependent Kerr constant, are reviewed. Recent progress on blue phase liquid crystal material development and device structures for lowering the operating voltage are introduced. Promising applications and remaining technical challenges are also discussed.

/pdf/polymer-stabilized-optically-isotropic-liquid-crystals-for-3gazz4at1n.pdf

Polymer-stabilized optically isotropic liquid crystals for next-generation display and photonics applications

A polymer-stabilized blue phase liquid crystal (BPLC) composite with a large Kerr constant (K∼13.7 nm/V2) is developed and its electro-optic properties characterized. In addition to the reduced operating voltage, this BPLC also exhibits a fast response time (∼1 ms), high contrast ratio (>1000:1), and relatively small hysteresis (<6%). It will undoubtedly accelerate the emergence of BPLC for next-generation display and photonic devices.

/pdf/a-large-kerr-constant-polymer-stabilized-blue-phase-liquid-34kcaubp0w.pdf

A large Kerr constant polymer-stabilized blue phase liquid crystal

We propose a numerical model based on Kerr effect for simulating the electro-optics of polymer-stabilized blue phase liquid crystal displays (BP-LCDs). Parameters affecting the electro-optics of BP-LCDs in in-plane-switching (IPS) structures, such as wavelength, temperature, electrode dimension, and cell gap are investigated. In addition, viewing angle and color shift of IPS BP-LCDs are studied.

/pdf/modeling-of-blue-phase-liquid-crystal-displays-4jyrye3zjx.pdf

Linghui Rao

Papers

Extended Kerr effect of polymer-stabilized blue-phase liquid crystals

Low voltage blue-phase liquid crystal displays

Polymer-stabilized optically isotropic liquid crystals for next-generation display and photonics applications

A large Kerr constant polymer-stabilized blue phase liquid crystal

Modeling of Blue Phase Liquid Crystal Displays