Search Results (568)

In the context of fifth-generation (5G) communications and the dawn of sixth-generation (6G) networks, a surged societal demand on bandwidth and data rate and more stringent commercial requirements on transmission efficiency, cost, and reliability are increasingly evident and, hence, driving the maturity of reconfigurable millimeter-wave (mmW) and terahertz (THz) devices and systems, in particular, liquid crystal (LC)-based tunable solutions for delay line phase shifters (DLPSs). However, the field of LC-combined electronics has witnessed only incremental developments in the past decade. First, the tuning principle has largely been unchanged (leveraging the shape anisotropy of LC molecules in microscale and continuum mechanics in macroscale for variable polarizability). Second, LC-enabled devices’ performance has yet to be standardized (suboptimal case by case at different frequency domains). In this context, this work points out three underestimated knowledge gaps as drawn from our theoretical designs, computational simulations, and experimental prototypes, respectively. The first gap reports previously overlooked physical constraints from the analytical model of an LC-embedded coaxial DLPS. A new geometry-dielectric bound is identified. The second gap deals with the lack of consideration in the suboptimal dispersion behavior in differential delay time (DDT) and differential delay length (DDL) for LC phase-shifting devices. A new figure of merit (FoM) is proposed and defined at the V-band (60 GHz) to comprehensively evaluate the ratios of the DDT and DDL over their standard deviations across the 54 to 66 GHz spectrum. The third identified gap deals with the in-depth explanation of our recent experimental results and outlook for partial leakage attack analysis of LC phase shifters in modern eavesdropping. Full article

Fast-response liquid crystal (LC) displays have attracted attention for use as gaming displays with high frame rate and field-sequential displays. This work presents an LC display mode with vertical alignment and horizontal electric field driving, which achieves millisecond-scale response time. The proposed LC display mode may achieve an average grayscale-to-grayscale response time of 1.42 ms using low-rotational-viscosity LC material, optimized device architecture, and overdrive, offering a potential application for gaming displays and color-sequential displays. Full article

Multilayer liquid crystal devices can offer enhanced optical functionalities for augmented reality and photonic applications, but fabrication remains severely limited by solvent incompatibility between photoalignment materials and underlying polymerized layers. Conventional photoalignment agents use aggressive solvents like N,N-dimethylformamide that damage polymerized substrates, necessitating protective interlayers. This study demonstrates a water-soluble photoalignment approach using AbA-2522 that eliminates these fabrication barriers. The water-soluble alignment material enables direct multilayer processing without layer damage while maintaining alignment quality equivalent to conventional materials. We successfully fabricate compact transmissive devices integrating liquid crystal polarization gratings with quarter-wave plates, achieving a first-order diffraction efficiency of 65.4% for 9 μm period gratings for linearly polarized incident light (λ = 457 nm). The multilayer structure exhibits highly selective polarization-dependent diffraction with efficiency ratios exceeding 10:1 between preferred and suppressed orders, eliminating external polarization control elements. Polarized optical microscopy confirms excellent alignment uniformity, while the fabrication process offers environmental benefits and reduced complexity. This approach establishes a practical pathway for advanced multilayer photonic devices critical for next-generation augmented reality systems and photonic integration, addressing fundamental challenges that have limited multilayer liquid crystal device development. Full article

Liquid Crystal Elastomers combine the elasticity of polymer networks with the anisotropic ordering of liquid crystals, thus enabling reversible shape modifications and stimulus responsive actuation. Unfortunately, manual LCE fabrication remains limited by operator-dependent variability, which can lead to inconsistent film thickness and manufacturing times inadequate for a mass production. This work presents a low-cost, automated manufacturing framework that redesigns the mechanical assembly steps of the traditional one-step LCE fabrication process. The design includes rubbing, slide alignment, spacer placement, and infiltration cell assembly to ensure consistent film quality and scalability. A customized Cartesian robot, built by adapting a modified X–Y core 3D printer, integrates specially designed manipulator systems, redesigned magnetic slide holders, automated rubbing tools, and supporting fixtures to assemble infiltration devices in an automated way. Validation tests demonstrate reproducible infiltration, improved mesogen alignment confirmed via polarized optical microscopy, and high geometric repeatability, although glass-slide thickness variability remains a significant contributor to deviations in final film thickness. By enabling parallelizable low-cost production, the designed hardware demonstrates its effectiveness in devising the scalable manufacturing of LCE films suited for advanced therapeutic and engineering applications. Full article

Perovskite solar cells (PSCs) have achieved remarkable efficiencies, yet further progress is limited by defect-induced nonradiative recombination and instability associated with uncontrolled crystallization. Here, we develop a protic ionic-liquid precursor engineering strategy based on methylammonium acetate (MAAc) for high-performance inverted (p–i–n) triple-cation perovskite solar cells. Systematic variation of the MAAc content reveals that a moderate concentration yields perovskite films with enlarged grains, suppressed pinholes, and strongly reduced residual PbI₂. Steady-state and time-resolved photoluminescence measurements, together with electrochemical impedance spectroscopy and light-intensity-dependent analysis, demonstrate that MAAc effectively suppresses trap-assisted nonradiative recombination, prolongs carrier lifetime, and increases recombination resistance without introducing additional transport losses. As a result, optimized inverted devices deliver a champion power conversion efficiency of 23.68% with a high open-circuit voltage of 1.21 V, a fill factor of ~0.83, negligible J–V hysteresis, and excellent device-to-device reproducibility. Moreover, the MAAc-2M devices exhibit markedly improved operational and shelf stability, retaining 73.2% of their initial efficiency after 30 days, compared to 53.2% for the control. This work establishes MAAc as an effective ionic-liquid additive that simultaneously governs crystallization and defect chemistry, offering a general route to efficient and stable inverted perovskite solar cells via protic ionic-liquid-assisted precursor engineering. Full article

Utilization of natural processes can reduce the complexity and production cost of any device by limiting the necessary steps in the production scheme, especially when it comes to fibers with periodic changes in refractive index. One such process is the nematic–isotropic phase separation of liquid crystal-based composite confined in 1D space. In this paper, we analyze the behavior of polymer-stabilized liquid crystal-based self-assembled periodic structures in an external electric field. We performed a detailed analysis regarding the reorientation of liquid crystal molecules under two orthogonal directions of the external electric field applied to the examined sample. It was demonstrated that the period of the polymerized structure remains constant until full reorientation, as the electric field induces the formation of new periodic defects in LC orientation. Consequently, the structure’s effective birefringence changes quite drastically, and this observed change depends on the direction of the electric field vector. The obtained results seem promising when it comes to application of the proposed periodic structures as voltage or electric field sensors operating as long-period fiber gratings or fiber Bragg gratings for the visible or near-infrared spectral regions. Full article

With the discovery of amorphous oxide semiconductors, a new era of electronics opened. Indium gallium zinc oxide (IGZO) overcame the problems of amorphous and poly-silicon by reaching mobilities of ~10 cm²/Vs and demonstrating thin-film transistors (TFTs) are easy to manufacture on transparent and flexible substrates. However, mobilities over 30 cm²/Vs have been difficult to reach and other materials have been introduced. Recently, polycrystalline In₂O₃ has demonstrated breakthroughs in the field. In₂O₃ TFTs have attracted attention because of their high mobility of over 100 cm²/Vs, which has been achieved multiple times, and because of their use in scaled devices with channel lengths down to 10 nm for high integration in back-end-of-the-line (BEOL) applications and others. The present review focuses first on the material properties with the understanding of the bandgap value, the importance of the position of the charge neutrality level (CNL), the doping effect of various atoms (Zr, Ge, Mo, Ti, Sn, or H) on the carrier concentration, the optical properties, the effective mass, and the mobility. We introduce the effects of the non-parabolicity of the conduction band and how to assess them. We also introduce ways to evaluate the CNL position (usually at ~E_C + 0.4 eV). Then, we describe TFTs’ general properties and parameters, like the field effect mobility, the subthreshold swing, the measurements necessary to assess the TFT stability through positive and negative bias temperature stress, and the negative bias illumination stress (NBIS), to finally introduce In₂O₃ TFTs. Then, we will introduce vacuum and non-vacuum processes like spin-coating and liquid metal printing. We will introduce the various dopants and their applications, from mobility and crystal size improvements with H to NBIS improvements with lanthanides. We will also discuss the importance of device engineering, introducing how to choose the passivation layer, the source and drain, the gate insulator, the substrate, but also the possibility of advanced engineering by introducing the use of dual gate and 2 DEG devices on the mobility improvement. Finally, we will introduce the recent breakthroughs where In₂O₃ TFTs are integrated in neuromorphic applications and 3D integration. Full article

Photoluminescent liquid crystals with photoluminescence (PL) and liquid-crystalline (LC) properties have attracted attention as PL-switching materials owing to their thermally induced phase transitions, such as crystal → smectic A/nematic → isotropic phase transitions. Our group previously developed tetrafluorinated tolane mesogenic dimers linked by flexible alkylene-1,n-dioxy spacers, demonstrating that the position of the tetrafluorinated aromatic ring critically influences the LC behavior. However, these compounds exhibited very weak fluorescence owing to an insufficient D–π–A character of the π-conjugated mesogens, which facilitated internal conversion from emissive ππ* to non-emissive πσ* states. We designed and synthesized derivatives in which the mesogen–spacer linkage was modified from ether to ester, thereby enhancing the D–π–A character. Thermal and structural analyses revealed spacer-length parity effects: even-numbered spacers induced nematic phases, whereas odd-numbered spacers stabilized smectic A phases. Photophysical studies revealed multi-state PL across solution, crystal, and LC phases. Strong blue PL (Φ_PL = 0.39–0.48) was observed in solution, while crystals exhibited aggregation-induced emission enhancement (Φ_PL = 0.48–0.77) with spectral diversity. In LC states, Φ_PL values up to 0.36 were maintained, showing reversible intensity and spectral shifts with phase transitions. These findings establish design principles that correlate spacer parity, phase behavior, and PL properties, enabling potential applications in PL thermosensors and responsive optoelectronic devices. Full article

Among the recently developed ferroelectric nematic liquid crystals, FNLC-919, synthesized by Merck Electronics KGaA, stands out for its stable, room-temperature, ferroelectric nematic (N_F) phase. This renders it a promising candidate for both fundamental research and device-level applications. In this study, we present a comprehensive experimental investigation of FNLC-919, focusing on its structural, optical, dielectric, and elastic properties in the paraelectric nematic (N) and the intermediate antiferroelectric phase (dubbed N_X) that occur in a temperature range between the N and N_F phases. Key material parameters such as ferroelectric polarization, viscosity, and nanostructure are characterized as functions of temperature in all mesophases, while the orientational elastic constants are determined only in the N and N_X phases. Our findings are compared with prior results concerning the benchmark compound DIO that also exhibits the phase sequence N-N_X-N_F and reveals a smectic-like mass density wave coinciding with antiferroelectric ordering in the N_X phase. Full article

High-speed realization of computer-generated holograms (CGHs) is a crucial problem in the field of modern 3D visualization and optical image processing system development. Binary CGHs can be realized using high-resolution, high-speed spatial light modulators such as ferroelectric liquid crystals on silicon devices or digital micro-mirror devices providing the high throughput of optoelectronic systems. However, the quality of holographic images restored by binary CGHs often suffers from distortions, background noise, and speckle noise caused by the limitations and imperfections of optical system components. The present manuscript introduces a method based on the optimization of CGH models directly in the optical system with a camera-in-the-loop configuration using effective direct search with a random trajectory algorithm. The method was experimentally verified. The results demonstrate a significant enhancement in the quality of the holographic images optically restored by binary-phase CGH models optimized through this method compared to purely digitally generated models. Full article

Building-integrated photovoltaics (BIPVs) can benefit not only from transparent but also from opaque modules that maximize light capture. We present haze-assisted luminescent solar concentrators (HALSCs) that integrate scattering and luminescence in multilayer designs. Polymer–liquid crystal composites with embedded dyes form micron-scale domains that act as broadband Mie scattering centers, while the dye provides spectral conversion. Monte Carlo ray-tracing simulations and experiments reveal that edge-emitted intensity increases with haze thickness but saturates beyond a threshold; segmenting the same thickness into multiple thinner layers enables repeated scattering, markedly enhancing side-guided emission. When coupled with crystalline silicon solar cells, multilayer HALSCs converted this optical advantage into enhanced photocurrent, with triple-layer devices nearly doubling output relative to transparent controls. These findings establish opacity–luminescence coupling and multilayer haze engineering as effective design principles, positioning HALSCs as practical platforms for advanced BIPVs and optical energy-management systems. Full article

Electromagnetic phase reconfigurability is a critical functionality for many emerging applications in electronics, defence, and other disruptive technologies. This work addresses a significant challenge in developing nematic liquid crystal (NLC)-based phase shifters: inaccurate and ambiguous calculations of differential phase shift, which can jeopardise on-time, on-budget device development. We investigate and correct two vulnerable cases of these calculation errors, demonstrated using a 60 GHz strip line and a 300 GHz coaxial line. For completeness, we also present a third case—a 1 mm long 60 GHz strip line—that correctly calculates phase shift, illustrating a “false positive” scenario. A unique contribution of this paper is the statistical analysis of how often these different phase shift processing errors occur during NLC delay line parameterisation. This statistical insight provides practical guidance for research and development. By numerically testing common assumptions, we establish traceable know-how to support smarter design decisions for radiofrequency (RF) engineers and academics. This work aims to advance NLC devices beyond classical display applications towards commercial viability. It also serves as a valuable reference and educational resource for students, physicists, and designers working on the precise phase characterisation of NLC-based reconfigurable devices. Full article

Liquid crystal elastomers (LCEs), as a class of smart materials, have attracted significant attention across soft robotics, biomedical engineering, and intelligent devices because of their unique capabilities to undergo large, reversible, and anisotropic deformations under external stimuli. Over the years, fabrication methods have advanced from conventional molding and thin-film processing to additive manufacturing, with 4D printing emerging as a transformative approach by enabling time-dependent, programmable shape transformations. Among the available methods, direct ink writing (DIW) and vat photopolymerization are most widely adopted, with ink chemistry, rheology, curing, and printing parameters directly governing mesogen alignment and actuation performance. Recent advances in LCE actuators have demonstrated diverse functionalities in soft robotics, including bending, crawling, gripping, and sequential actuation, while biomedical applications span adaptive tissue scaffolds, wearable sensors, and patient-specific implants. This review discusses the conceptual distinction between 3D and 4D printing, compares different additive manufacturing techniques for LCE, and highlights emerging applications in the field of soft robotics and biomedical technologies. Despite rapid progress in LCE, challenges remain in biocompatibility, long-term durability and manufacturing scalability. Overall, innovations in 4D printing of LCEs underscores both the promise and the challenges of these materials, pointing toward their transformative role in enabling next-generation soft robotic and biomedical technologies. Full article

Polymer-dispersed liquid crystal (PDLC), as an electrically controlled dimming material, has broad application prospects in various fields, including smart glass, display technology, and optical devices. However, traditional PDLC materials still face some challenges in practical applications, such as a high driving voltage and insufficient optical contrast, which limit their further application in high-performance optoelectronic devices. In this study, PDLC composite films exhibiting low-voltage operation (23 V), high contrast ratios (135), and rapid response times (T_R ~1.28 ms, T_D ~48 ms) were developed. This was achieved by modifying the chain length of the crosslinking agent and polymer monomer as well as by incorporating molybdenum disulfide (MoS₂) nanosheets. It shows a good regulation ability in the sunlight range (ΔT_sol = 63.92%, ΔT_lum = 73.97%). Simultaneously, the various chemical bonds inside the film and its special network structure enable it to exhibit a good radiative cooling effect. The indoor sunlight simulation tests showed that the indoor temperature decreased by 5 °C. This study provides valuable ideas for the development and preparation of smart windows with high efficiency and energy savings. Full article

The permanent memory effect in polymer-dispersed liquid crystal systems imparts unique properties to these devices, making them well-suited for digital memory applications. By investigating the impact of homogeneous alignment layer types on this effect, we successfully developed and tested a proof-of-concept prototype capable of recording information in both opaque and transparent states within a digital process. Full article