Alignment properties of a ferroelectric nematic liquid crystal on the rubbed substrates.

The orientation characteristics of FNLC-919, a new material with a ferroelectric nematic phase at room temperature, were investigated. Its alignment characteristics varied greatly depending on the relative rubbing direction on both substrates of a liquid crystal cell. In a cell where the two substrates were rubbed in the same direction, they were arranged homogeneously along the rubbing direction without domains or defects in the ferroelectric nematic phase. In a cell where the two substrates were rubbed in the anti-parallel direction, the two domains were twisted in the opposite direction. We quantitatively obtained the twisted direction and angle by matching the experimental data and calculation results using Jones matrix calculations. From the electro-optical experiment, it was confirmed that the polarization direction was opposite to the rubbing direction. In addition, the wavelength and temperature dependence of birefringence was measured for FNLC-919. In a cell where the rubbing direction between two substrates was 90°, two domains of opposite directions were observed in the nematic phase. When it becomes a ferroelectric nematic phase on cooling, the twist is determined to be only in one direction. The twist direction and angle were quantitatively obtained in the nematic and ferroelectric nematic phases. It was twisted more in the ferroelectric nematic phase than in the nematic phase.

Electro-optical synaptic characteristics of ferroelectric liquid crystals for artificial intelligence.

We propose electro-optical synaptic devices using surface-stabilized ferroelectric liquid crystals. Typical synaptic characteristics were observed for varying pulse time intervals, numbers of pulses, and signal voltages. Plasticity only occurred when pulses were applied at intervals shorter than the response time of the ferroelectric liquid crystal. Moreover, the plasticity increased with a higher pulse voltage and number of pulses. This demonstrates the importance of repeated learning. The synaptic weights required to make connections through learning in an artificial neural network can be determined by tuning the pulse signal. We discuss the high-speed computational potential of optical neuromorphic devices using liquid crystals.

Management of overwintering pine sawyer beetle, Monochamus alternatus with colonized Beauveria bassiana ERL836.

Monochamus alternatus is a major forest pest that spreads pine wilt disease in pine trees as a vector of pine wilt nematodes. Chemical insecticides used as fumigants to control overwintering M. alternatus in forests are highly toxic to the environment, so we investigated entomopathogenic fungus Beauveria bassiana ERL836 as an eco-friendly and alternative material to control overwintering M. alternatus. In this work, we evaluated the insecticidal activity of B. bassiana ERL836 against M. alternatus adults, the possibility of fungal colonization on pine tree bark, and finally the control efficacy of fungal pre-treatment on pine tree logs against emerging M. alternatus adults in semi-field and field conditions. M. alternatus adults were killed on the pine tree logs pre-treated with the B. bassiana ERL836. White conidia were observed not only on the surface of the dead adults but also on the pine tree logs, suggesting that the adults were killed by the fungus on the pine. A formulated ERL836 powder treatment on larvae-infested pine logs showed high insecticidal activity against adults, similar to that with the fungal powder suspension treatment, but we demonstrated that using the fungal powder was simpler than using the suspension in field conditions. Even in the field condition, the fungal powder treatment showed high insecticidal activity against M. alternatus adults, which we attribute to its ability to maintain fungal activity for a long time in field conditions by covering the pine tree logs with a film during overwintering. We confirmed that the risk that fungus-infected M. alternatus adults would spread the fungus to other non-target forest insects was low. Thus, even a high-concentration treatment in a specific area is unlikely to transmit the fungus outside that area, so it can be safely used to control this pine wilt nematode vector in forest ecosystems.

Hacking detection based on the elastic properties of liquid crystals in different phases.

We present a security device that can detect and block hacking using the characteristics of liquid crystals. This device is based on a liquid crystal cell consisting of a uniformly aligned layer and a photo-alignment layer. To inscribe a pattern, the device is illuminated when the liquid crystal is in the smectic phase. The resulting image is invisible after light irradiation. Heating to the nematic phase improves this alignment and reveals the recorded pattern. Returning to the smectic phase distorts the pattern. Because the pattern is not shown without heating and the trace of the pattern does not disappear once viewed, it is possible to detect whether data has been hacked. The device is easy to fabricate, cost-effective, and sensitive to outside intrusion.

Tuning photoluminescence spectra of MoS2 with liquid crystals.

The photoluminescence (PL) and Raman spectra of molybdenum disulfide (MoS2) can be tuned with liquid crystals. A nematic liquid crystal, 5CB, was aligned in a zigzag direction on an MoS2 monolayer flake. The PL and A1g Raman mode peaks of the MoS2 monolayer were shifted by 46 meV and 2 cm-1, respectively, owing to the interaction between MoS2 and the liquid crystal. Based on Lorentzian fitting analysis, it was confirmed that the peak positions and intensity ratios of the trion PL and exciton PL varied with the phase transition of the liquid crystal. This phenomenon was possibly caused by the transfer of electrons from MoS2 to the liquid crystal. This electron transfer varies with the temperature-dependent change in the liquid crystal phase. Therefore, the PL spectra of MoS2 can be tuned simply by controlling the phase, without changing the type of added material.

Bidirectional rotation control of a carbon fiber in nematic liquid crystal using AC electric field.

Colloidal particles dispersed in nematic liquid crystals are aligned along the orientation that minimizes the elastic free energy. Through applying an electric field to a nematic colloidal system, the orientation of the director can change. Consequently, colloidal particles realign to minimize the total free energy, which is the sum of the elastic and electric free energies. Herein, we demonstrate that if the preferred rotation directions given by the electric and elastic free energies are different during realignment, the rotation direction of the particle can be controlled by how we apply the electric field. When the strength of the electric field gradually increases, the particles rotate in the same direction as the rotation of the director. However, when a sufficiently high electric field is suddenly applied, the particles rotate in the opposite direction. In this study, we analyzed the effect of free energy on the bidirectional rotation behavior of the particles using a theoretical model. This study provides an effective approach to control the rotational behavior of colloidal particles over a wide-angle range between two orientational local minima.

Characterization of T-DNA insertion mutants with decreased virulence in the entomopathogenic fungus Beauveria bassiana JEF-007.

The bean bug, Riptortus pedestris, is a major agricultural pest that reduces crop quality and value. Chemical pesticides have contributed to pest management, but resistance to these chemicals has significantly limited their use. Alternative strategies with different modes of action, such as entomopathogenic fungi, are therefore of great interest. Herein, we explored how entomopathogenic fungi can potentially be used to control the bean bug and focused on identifying virulence-related genes. Beauveria bassiana (JEF isolates) were assayed against bean bugs under laboratory conditions. One isolate, JEF-007, showed >80 % virulence by both spray and contact exposure methods. Agrobacterium tumefaciens-mediated transformation (AtMT) of JEF-007 generated 249 random transformants, two of which (B1-06 and C1-49) showed significantly reduced virulence against Tenebrio molitor and R. pedestris immatures. Both species were used for rapid screening of virulence-reduced mutants. The two transformants had different morphologies, conidial production, and thermotolerance than the wild type. To determine the localization of the randomly inserted T-DNA, thermal asymmetric interlaced (TAIL) PCR was conducted and analysis of the two clones found multiple T-DNA insertions (two in B1-06 and three in C1-49). Genes encoding complex I intermediate-associated protein 30 (CIA30) and the autophagy protein (Atg22) were possibly disrupted by the T-DNA insertion and might be involved in the virulence. This work provides a strong platform for future functional genetic studies of bean bug-pathogenic B. bassiana. The genes putatively involved in fungal virulence should be experimentally validated by knockdown in future studies.

Production of antibacterial Bombyx mori cecropin A in mealworm-pathogenic Beauveria bassiana ERL1170.

Efforts are underway to produce antimicrobial peptides in yellow mealworms (Tenebrio molitor), which can be developed as more effective and safer animal feed additives. In this work, we expressed Bombyx mori (Bm) cecropin-A in mealworms by the infection of transformed entomopathogenic Beauveria bassiana ERL1170. The active domain of Bm cecropin A gene was tagged with a signal sequence of B. bassiana for extracellular secretion, and the fragment was inserted into ERL1170 by the restriction enzyme-mediated integration method. Transformant D-6 showed antibacterial activity against Bacillus subtilis and Listeria monocytogenes. Against T. molitor larvae, D-6 had similar mortality to wild-type, and D6-infected mealworm suspension showed strong antibacterial activity against the two bacteria, but not in the wild-type-infected mealworms, thereby increasing the value of mealworms as animal feed additives.

Mapping of the atomic lattice orientation of a graphite flake using macroscopic liquid crystal texture.

The electronic properties of graphene depend critically on its lattice orientation and edge type. However, it is very difficult to identify them, and they are accessible only using sophisticated tools. In this paper, we show an easy and reliable way to reveal the lattice orientation and edge type of graphene and graphite flakes, i.e. multi-layered graphene. Nematic liquid crystals have the potential to align themselves into three symmetric and equivalent orientations on crystalline graphite. The director of macroscopic texture due to the elasticity indicates the lattice orientation of the top graphite layer. By analyzing the director orientation using a polarizing optical microscope, we were able to show the lattice orientation, chiral angle and edge type of graphene and graphite flakes on the macroscopic scale. As liquid crystals are soft and easily removable, our technique has little chance of influencing the following processes for graphene manipulation.

Characteristics of localized surface plasmon resonance of nanostructured Au patterns for biosensing.

Periodic arrays of pseudotetrahedal-shaped gold nanoparticles were fabricated using nanosphere lithography (NSL) and examined for localized surface plasmon resonance (LSPR). The dependence of the LSPR on particle size of the periodic gold nanostructures was explored for potential application as a new biosensor. With increasing size and height of the Au nanoparticles, the absorption peak of the LSPR shifts to the longer wavelength and becomes relatively sharper. With thinner metal deposition or finer Au nanostructure, the absorption signal varies more sensitively for the changes in the Au particle size. The binding affinity study for biotin-streptavidine system on the Au nanopat-terns resulted in blue-shifted absorption signal, opening up the possibility of the nanostructured Au pattern as a new LSPR biosensor.