Anisotropic crystal growth in blue phase I transitioned from a uniformly oriented cholesteric phase.

Phase transitions in blue phase liquid crystals (BPLCs) have attracted significant attention from the technical perspective of BP orientation control and the theoretical perspective of analogs with crystalline solids. The phase transition phenomena in BPs significantly depend on the phase state before the transition. In this study, we focused on the cholesteric (Ch)-BPI phase transition and found that BPI crystals exhibited a square shape upon the phase transition from the uniformly oriented Ch phase to the BPI phase. This square crystal shape was common across three BPLC materials with different elastic constants, and the shape reflected the crystal axis. The in-plane crystal orientation correlates with the easy axis on the substrate surface, suggesting that the [011] axis tends to coincide with the easy axis. However, the easy axis has little effect on the crystal growth rate. Furthermore, scratches on the substrate surface promoted nucleation. Based on this behavior, it was demonstrated that the nucleation position and density could be controlled by intentionally disturbing the Ch orientation by locally changing the easy axis using photoalignment. This study focused on the anisotropic crystal growth of BPI, providing interesting insights into LC phase transitions and soft matter crystal growth. In addition, it offers techniques for the fabrication of large BPI crystals, contributing to the enhanced electrical and optical performances of BPLC devices.

Tunable polarization volume gratings based on blue phase liquid crystals.

A large-angle polarization volume grating (PVG) with circular-polarization selectivity is demonstrated using a three-dimensional chiral liquid crystal with simple cubic symmetry - the blue phase (BP) II. We confirm defect-free alignment of the BP crystal on a periodically patterned substrate down to a period of 700 nm, with Kossel diagrams and far-field diffraction patterns suggesting that the lattice becomes slanted within the cell to accommodate to the imprinted pattern. We further demonstrate a tunable PVG by exploiting the external field-responsivity of BPs, making this PVG attractive for a wide range of applications from tunable photonics to augmented reality.

Generation of a focused optical vortex beam using a liquid crystal spiral zone plate.

Optical vortices (OVs) with orbital angular momenta show promise for various optical applications. Spiral zone plates (SZPs) can generate a focused OV and are thus used in applications like edge-enhanced imaging. However, conventional SZPs have low diffraction efficiency because they operate based on amplitude modulation. This study proposes a liquid crystal spiral zone plate (LCSZP) that operates based on phase modulation and demonstrates the generation of a focused OV with high efficiency and electric tunability. The LCSZP has no threshold voltage owing to its homeotropic/planar hybrid alignment regions, and it can find applications in imaging, laser processing, and optical manipulation.

Three-dimensional lattice deformation of blue phase liquid crystals under electrostriction.

In this work, we investigate the three-dimensional lattice deformation of blue phase (BP) liquid crystals under electrostriction. Using the in situ measurement of light diffraction signals from a twinned crystal, we propose a method to experimentally determine the lattice constants of BPs under an electric field; the overlap angle in the diffraction pattern of BP twinning domains gives the ratio of lattice constants in the lateral direction of the field, which can be analyzed together with the Bragg reflection peak wavelength along the field direction to yield three-dimensional lattice constants. The obtained values are confirmed to show good agreement with the diffraction data measured from a converging monochromatic light. Furthermore, by applying the method to BPs in a thin cell and specifying the transitions of azimuthal orientation, three-dimensional lattice deformation of BP I crystals and evolution of the azimuthal orientation are clarified under the electrostriction. Results reveal that the BPs confined to thin films undergo discrete elongation along the field direction and the BP I crystal undergoes larger lattice deformation in the field-perpendicular directions than that along the field. Our work allows a relatively easy determination of three-dimensional lattice constants of deformed BP crystals under an electric field, and the obtained results provide important insights into the understanding of the electrostriction behaviour of BPs towards improvement of the electro-optical performance of BP devices in practical applications.

Extended conjugation of ESIPT-type dopants in nematic liquid crystalline phase for enhancing fluorescence efficiency and anisotropy.

Organic compounds capable of excited-state intramolecular proton transfer (ESIPT) show fluorescence with a large Stokes shift and serve as solid-state emitters, luminescent dopants, and fluorescence-based sensing materials. Fluorescence of ESIPT molecules is usually increased in the solid state, but is weak in solvents due to the accelerated non-radiative decays by rotational motions of a part of the molecular core in these environments. Here we report, using a representative ESIPT motif 2-(2-hydroxyphenyl)benzothiazole (HBT), the extended-conjugation strategy of keeping sufficient fluorescence efficiency both in the solid state and in organic media. The introduction of an alkyl-terminated phenylene-ethynylene group into the HBT molecule dramatically enhances the fluorescence quantum yield from 0.01 to 0.20 in toluene and from 0.07 to 0.32 in a representative room-temperature nematic liquid crystal, 4-pentyl-4'-cyano biphenyl (5CB). The newly-synthesized CnP-C[triple bond, length as m-dash]C-HBT (n = 5 or 8) serves as a fluorescent dopant in 5CB and exhibits anisotropic fluorescence with the order parameter of 0.48, where the luminescence is controlled by the applied electric-field. The enhanced emission efficiency is rationalized by the larger height of energy barrier for the ESIPT process due to the introduction of phenylene-ethynylene groups.

[A Case of Effective Endovascular Treatment for Recurrent Bleeding from Advanced Breast Cancer].

A-58-year-old woman was diagnosed with breast cancer 8 years ago at another hospital, but refused surgical treatment. From 2 years ago, her skin invasion of cancer lesions began bleeding. The patient required frequent blood transfusions due to anemia associated with repeated bleeding. She was referred to our department for local treatment and palliative care. Diagnostic imaging revealed multiple lung, bone and liver metastasis. The patient refused to receive systemic chemotherapy, and she was recommended radiation therapy for repeated massive bleeding, but her consent was not obtained. She agreed to receive arterial embolization from the tumor-bearing vessels plus intravenous anti-cancer drug therapy. The hemostatic effect was observed for 4 to 5 weeks per treatment, and tumor reduction was also observed. She received a total of 6 treatments during 8 months until her death. These treatments were effective in maintaining quality of life at the end of life.

Topologically Protected Generation of Stable Wall Loops in Nematic Liquid Crystals.

The nematic liquid crystal (LC) director field can contain defects that are both singular and nonsingular, but nonsingular defects with an integer winding number of the director are typically metastable because of their high energy. We demonstrate topology-mediated generation and stabilization of nonsingular wall loops in a sandwich-type LC cell by combining a patterned substrate with a planar substrate. We implement a design which imposes a topological constraint on a singular disclination loop such that it irreversibly annihilates upon application of a field, and it results in the generation of a stable nonsingular wall loop when the field is removed. Theoretical modeling agrees with experimental observations, providing insight into the wall generation mechanism and its stability. The concept to stabilize high-energy structures through orientation-patterning-defined topological constraints extends our ability to control orientationally ordered matter.

Highly Miscible Hybrid Liquid-Crystal Systems Containing Fluorescent Excited-State Intramolecular Proton Transfer Molecules.

Doping of luminescent molecules in a nematic liquid-crystal (LC) host is a convenient approach to develop light-emitting LC displays that would be a promising alternative to conventional LC displays. The requirements for the luminescent guest molecules include high miscibility in the host LC, high-order parameters in the host LC media to show anisotropic luminescence, lack of self-absorption, transparency in the visible region, and a large photoluminescence quantum yield independent of its concentration. To address these issues, here, we newly synthesize a highly miscible and fluorescent excited-state intramolecular proton transfer molecule, C4-C≡C-HBT, based on 2-(2-hydroxyphenyl)benzothiazole (HBT). This compound is highly miscible in a conventional room-temperature nematic LC 4-pentyl-4'-cyano biphenyl (5CB) up to 14 wt % (∼12 mol %) and exhibits a large photoluminescence quantum yield of ΦFL = 0.32 in the 5CB host, both of which were achieved by the introduction of an alkynyl group into the HBT core. C4-C≡C-HBT possesses a high-order parameter of S = 0.46 in 5CB, and the C4-C≡C-HBT/5CB mixtures show anisotropic fluorescence whose intensity is controlled by the applied electric field. A patterned image is demonstrated, which is not visible under an ambient environment but is readable upon UV illumination, relying on the orientational differences of ordered C4-C≡C-HBT molecules.

Field strength and frequency tunable, two-way rotation of liquid crystal micro-particles dispersed in a liquid crystal host.

Liquid crystal (LC) micro-particles are functional materials possessing anisotropies of LCs originating from their inner molecular alignment, and are fabricated by polymerizing pre-aligned rod-like molecules in the LC state. Here we demonstrate field strength and frequency tunable two-way rotation control of LC micro-particles in a LC host, and unravel its mechanism by theoretically calculating the contributing free energies. Cuboid-shaped micro-particles with inner molecular alignment along the long axis are fabricated via two-photon excited direct laser writing, and dispersed in a dual-frequency (DF) LC to be electrically driven by a voltage applied in the in-plane direction of the cell. Under an electric field, the particles rotate either clockwise or anticlockwise to align the inner molecular alignment parallel or perpendicular to the applied field; however, unlike conventional LCs, the rotation direction depends not only on the frequency, but also on the strength of the field. The complex motion is found to be the result of a delicate balance between the elastic energy of the host LC around the particle and the electrostatic energies of the host and the particle. Understanding complex rotational motion in LC/LC-particle composites is a step towards the development of advanced switching materials with superior performance.

Polychromatic Optical Vortex Generation from Patterned Cholesteric Liquid Crystals.

Generation of optical vortices is described in cholesteric liquid crystals with a singular point in the spatial distribution of a helix phase. The phenomenon uses the fact that a Bragg reflected light phase varies in proportion to the spatial phase of the helix, both at normal and oblique incidences. Our proposal enables high-efficiency, polychromatic generation of optical vortices without the need of a cumbersome fabrication process and fine-tuning.

Reversible switching of liquid crystal micro-particles in a nematic liquid crystal.

Liquid crystal micro-particles are functional materials possessing optical and dielectric anisotropies originating from the arrangement of rod-like molecules within the particles. Although they can be switched by an electric field, particles dispersed in isotropic hosts usually cannot return to their original state, because there is no restoration force acting on the particles. Here, we describe reversible switching of liquid crystal micro-particles by dispersing them in a nematic liquid crystal host. We fabricate square micro-particles with unidirectional molecular alignment and investigate their static and dynamic electro-optic properties by applying an in-plane electric field. The behavior of the micro-particles is well-described by the theoretical model we construct, making this study potentially useful for the development of liquid crystal-liquid crystal particle composites with engineered properties.

Molecular Packing Structure of Mesogenic Octa-Hexyl Substituted Phthalocyanine Thin Film by X-ray Diffraction Analysis.

The molecular packing structure in a thin film of the liquid crystalline phthalocyanine, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), which is a promising small-molecular material for solution-processable organic thin-film solar cells, has been investigated by X-ray diffraction (XRD) measurement. The crystal structure of C6PcH2 in the spin-coated film was determined to be a centered rectangular structure (a = 36.4 Å, b = 20.3 Å). The tilt angle of the phthalocyanine core normal vector was 34-39° from the column axis, and the shortest intermolecular distance was 3.9-4.0 A. The crystal structure determined by XRD analysis was ascertained to be consistent with that calculated by Fourier analvsis.

Polarization-independent submillisecond phase modulation utilizing polymer/short-pitch cholesteric liquid crystal composite.

A broadband, polarization-independent phase modulation spanning the visible range is demonstrated using a polymer/cholesteric liquid crystal composite with optical pitch in the ultraviolet. Polarization insensitivity is achieved as a result of two effects: (1) optical anisotropy of the rod-like molecules is canceled out by the short helical pitch, and (2) stabilization of the Grandjean texture by the polymer network suppresses depolarization. Polarization-independent modulation of the refractive index by approximately 0.045, corresponding to a phase modulation of π at 500 nm, is achieved with submillisecond response times. Our material system opens new avenues for polarization-independent, tunable optical devices, such as narrow bandpass filters, gratings, and adaptive lenses.

Apparent Diffusion Coefficient Value Is Not Dependent on Magnetic Resonance Systems and Field Strength Under Fixed Imaging Parameters in Brain.

OBJECTIVE: The aim of the study was to investigate the causes of apparent diffusion coefficient (ADC) measurement errors and to determine the optimal scanning parameters that are independent of the field strength and vendors of the magnetic resonance (MR) system. MATERIALS AND METHODS: Brain MR images of 10 healthy volunteers were scanned using 6 MR scanners of different field strengths and vendors in 2 different institutions. Ethical review board approvals were obtained for this study, and all volunteers gave their informed consents. Coefficient of variation (CV) of ADC values were compared for their differences in various MR scanners and in the scanned subjects. RESULTS: The CV of ADC values for 6 different scanners of 6 brains was 3.32%. The CV for repeated measurements in 1 day (10 scans per day) and in 10 days (scan per day for 10 days) for 1 subject was 1.72% and 2.96%, respectively (n = 5, P < 0.001). The CV of measurements for 10 healthy subjects was 5.22%. The measurement errors of the ADC values for 6 different MR units in 1 subject were higher than the intrascanner variance for the same subject but were lower than the intersubject variance for the same scanner. CONCLUSIONS: The variance in the ADC values for different MR scanners is reasonably small if appropriate scanning parameters (repetition time, >3000 ms; echo time, minimum; and high enough signal-to-noise ratio of high-b diffusion-weighted image) are used.

High-speed driving of liquid crystal lens with weakly conductive thin films and voltage booster.

Liquid crystal (LC) lenses with weakly conductive thin films are known to have driving voltages of several volts, which are much smaller than those of devices without them; however, their response characteristics have not been investigated in much detail. Here, we show that low-voltage LC lenses, with the help of an overdrive pulse, can show response times of several 10 ms, which are comparable with voice coil motors currently used for focus-tuning of mobile cameras. We provide data on the lens power as well as real images captured using a lens module and a camera; we also present a compact circuit design that can boost a 3.5 V(rms) square pulse from a mobile battery to 15 V(rms). The results of this study should accelerate the use of LC lenses in mobile applications.

Photonic band structure and transmission analysis of cholesteric blue phase II: electrostriction in the [100] direction.

The photonic band structure and transmission properties of a cholesteric blue phase II liquid crystal, which is elongated in the [100] direction by electrostriction, are analyzed by finite-difference time-domain method. The simple cubic lattice deforms into a tetragonal lattice under the influence of an electric field, resulting in a change of the photonic band structure. Moreover, we show that the circular polarization dependence of the transmittance spectrum changes in an electric field, a behavior that has yet to be observed in experiment.

Tunable enhanced 0th-order transmission in a metal-dielectric hole array covered with a subwavelength liquid crystal layer.

We demonstrate tunable, enhanced 0th-order transmission through a metal-dielectric nanohole array device with a subwavelength-thick liquid crystal (LC) layer. The LC filled the nanoholes and formed a subwavelength covering layer, which is then capped by a top cover layer. The wavelength where the transmittance dip associated with the LC occurs is determined by the anisotropic refractive-index component of the LC, which is normal to the surface of the hole array. A low-refractive-index cover layer suppresses unwanted higher-order diffraction, which results in an enhancement of the 0th-order transmission, which is closely related to laterally propagating surface plasmon polaritons. The proposed design is expected to help realize tunable plasmonic devices with high optical transmittance.

Transparaumbilical Intravariceal Sclerotherapy for Duodenal Varices Using Outflow Embolization.

A 55-year-old patient was admitted for variceal treatment, a complication of chronic portal hypertension and liver cirrhosis. Imaging studies revealed prominent duodenal varices, the pancreaticoduodenal vein as its afferent pathway, a drainer vessel into the inferior vena cava, and a paraumbilical vein. We successfully performed complete obliteration of the varix, including its afferent and efferent vessels, via the paraumbilical vein approach.

Percutaneous transhepatic sclerotherapy for ascending colonic varices due to left-sided portal hypertension.

Left-sided portal hypertension (LSPH) causes varices and splenomegaly due to splenic vein issues. Colonic varices are rare and lack standardized treatment. We report the successful treatment of colonic varices caused by LSPH, by addressing both the afferent and efferent veins. A 70-year-old man with distal cholangiocarcinoma had surgery without splenic vein resection, leading to proximal splenic vein stenosis and varices at multiple locations. Percutaneous transhepatic splenic venography revealed that collateral veins flowed into the ascending colonic varices and returned to the portal vein. Complete thrombosis of the varices was achieved by injecting sclerosants and placing coils in both the afferent and efferent veins. The procedure was safe and effective, with no variceal recurrence. This approach provides a minimally invasive option for treating colonic varices associated with LSPH.

A rat-based preclinical platform facilitating transcatheter hepatic arterial infusion in immunodeficient rats with liver xenografts of patient-derived pancreatic ductal adenocarcinoma.

Liver metastases from pancreatic ductal adenocarcinoma (PDAC) are highly fatal. A rat-based patient-derived tumor xenograft (PDX) model is available for transcatheter therapy. This study aimed to create an immunodeficient rat model with liver xenografts of patient-derived primary PDAC and evaluate efficacy of hepatic arterial infusion chemotherapy with cisplatin in this model. Three patient-derived PDACs were transplanted into the livers of 21 rats each (totally, 63 rats), randomly assigned into hepatic arterial infusion, systemic venous infusion, and control groups (n = 7 each) four weeks post-implantation. Computed tomography evaluated tumor volumes before and four weeks after treatment. Post-euthanasia, resected tumor specimens underwent histopathological examination. A liver-implanted PDAC PDX rat model was established in all 63 rats, with first CT identifying all tumors. Four weeks post-treatment, arterial infusion groups exhibited significantly smaller tumor volumes than controls for all three tumors on second CT. Xenograft tumors histologically maintained adenocarcinoma features compared to original patient tumors. Ki67 expression was significantly lower in arterial infusion groups than in the other two for the three tumors, indicating reduced tumor growth in PDX rats. A liver-implanted PDAC PDX rat model was established as a rat-based preclinical platform. Arterial cisplatin infusion chemotherapy represents a potential therapy for PDAC liver metastasis.