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High tilt angle (45 °) ferroelectric liquid crystal (F L C) in surface stabilized geometry, having no chiral smectic A (S m A ∗) phase, has been studied for the reorientation of the smectic layers near the transition temperature (T c). The electro-optical studies have shown the stripe domain formation in which the liquid crystal molecules are aligned along the rubbing direction, but the smectic layers are tilted away from the rubbing direction at room temperature. In such high tilt angle F L C s , the molecular alignment and smectic layer formation start from bottom and top rubbed grooves at T c. The domain formation of the FLC takes place in the middle of the top and bottom surfaces due to the frustration of the dipolar interaction. The smectic layer switching is observed by optical microscopy and confirmed by the dielectric spectroscopy method near T c of S m C ∗ and chiral nematic phases. Domain switching has shown a larger switching angle than the molecular tilt angle within the smectic layer. These studies are expected to be significant for understanding the smectic layer structure and the domain switching process, which may pave the way for large optical switching devices. [ABSTRACT FROM AUTHOR]

A great deal of effort has been recently devoted to the study of dielectric relaxation processes in ferroelectric nematic liquid crystals, yet their interpretation remains unclear. In this work, we present the results of broadband dielectric spectroscopy experiments of a prototypical ferroelectric nematogen in the frequency range 10 Hz–110 MHz at different electrode separations and under the application of DC bias fields. The results evidence a complex behavior in all phases due to the magnitude of polar correlations in these systems. The observed modes have been assigned to different relaxation mechanisms based on existing theoretical frameworks. [ABSTRACT FROM AUTHOR]

Owing to the passive nature of liquid crystal (LC) materials, achieving luminous displays using pure LC materials is challenging. In addition, it is difficult to achieve a fast switching time using pristine ferroelectric LC devices without compromising their cell thickness. Herein, we have developed a fast switching and highly luminescent electro-optical device by dispersing a minute concentration of bimetallic nanoparticles (Au@Ag NPs) having a spherical gold core and a silver shell within a ferroelectric liquid crystal (FLC) host matrix, ZLI3654. Au@Ag core–shell NPs having synergic attributes of both counterparts were successfully synthesized by a facile seed-mediated route. The Au core helps to tune the shape of the Ag shell and provides enhanced electron density as well as improved stability against oxidation. Introducing nanoparticles induces little structural modifications to the host FLC, resulting in an improvement in the mesogenic alignment. Interestingly, ∼29-fold enhancement in the photoluminescence (PL) intensity is observed on dispersing 0.25 wt% of Au@Ag NPs into the FLC host matrix. The enhanced electromagnetic field in the FLC-nanocomposite is attributed to the Localized Surface Plasmon Resonance of Au@Ag NPs, which strengthens the photon absorption rates by the FLC molecules, culminating in the massive enrichment of the PL intensity. In addition, the improved localized electric field inside the FLC device led to a noticeable enhancement in the spontaneous polarization, dielectric permittivity, and, most interestingly, ∼53% fastening in the switching time at an optimum concentration (0.25 wt%) of Au@Ag NPs. The improved electro-optical parameters of the Au@Ag NPs/FLC composite have been compared with the performance of both pristine Au NPs/FLC and Ag NPs/FLC composites, respectively, for the comprehensiveness of the study. The present study paves a systematic way to develop FLC-based advanced electro-optical devices with faster switching and higher luminescence properties. [ABSTRACT FROM AUTHOR]

Optically isotropic polymer stabilized liquid crystals with low haze (≈1% at 550 nm), large (≈0.09) field induced refractive index variation, and fast (<0.1 ms) relaxation time are reported. The impressive improvement compared to previous studies using conventional nematic liquid crystals are due to both the addition of novel highly polar ferroelectric nematic liquid crystals that decrease the required field to achieve the theoretically predicted refractive index variation and of the 6 wt.% of chiral dopant with high helical twisting power that suppressed the haze and made the system reversible with fast relaxation. It is also shown that the field induced refractive index variation can be increased over to 0.1 by using high intensity UV light for polymer stabilization. Although such polymer structure is not completely isotropic, it still provides polarization independent optical properties for normal incidence. Since fast and large switching of focal length is essential in AR/VR glasses, these systems offer significant potential for applications in highly tunable microlens arrays. [ABSTRACT FROM AUTHOR]

Viscosity, elasticity, and viscoelastic properties are one of the most fundamental properties of liquid crystalline materials; the main problem in determining these properties is the multitude of physical parameters needed to determine the values of elasticity and viscosity constants. In this paper, a number of different measurement methods for the complete characterization of viscoelastic properties for smectic liquid crystalline materials and their mixtures are analyzed, both theoretically and experimentally. The way in which viscoelastic material constants are determined depends mainly on the application/purpose of the materials under study. The subject of this work was to review the methods used to determine viscoelastic effects in ferroelectric and antiferroelectric chiral liquid crystals, their mixtures, composite materials, and even in dielectric systems, which would bear the hallmark of a universal method allowing the application of sufficiently low electric fields. In the case of chiral liquid crystals with ferroelectric and antiferroelectric phases and their subphases, the following assumption applies: fulfilment of Hooke's law (in the case of elastic coefficients) and preservation of laminar flow (in the case of viscosity coefficients). [ABSTRACT FROM AUTHOR]

The dielectric properties of synclinic (ferroelectric SmC*) and anticlinic (antiferroelectric SmCA*) smectic liquid crystals composed of molecules of one chiral version (S) are presented and compared with properties of racemic mixture (R, S), showing SmC and SmCA phases. The racemic mixture completely loses its ferroelectric and antiferroelectric properties. Surprisingly, only one dielectric mode observed in the antiferroelectric SmCA* phase disappeared in the dielectric response of the racemic SmCA phase. Additionally, we observed that in the SmC phase, seen in the racemic mixture, the weak dielectric mode (named the X mode) is detected, which seems to be the continuation of the PL mode existing in the racemic SmCA. Moreover, this mode in the racemic SmC has nothing to do with the Goldstone mode, typical for the SmC* phase. This paper describes in detail the real and imaginary parts of dielectric permittivity in smectic phases for the enantiomer and racemate with and without a DC field, compares the properties of the X and PL modes, and discusses the full scheme of dielectric modes in enantiomer and racemate. [ABSTRACT FROM AUTHOR]

Valleytronics has attracted much attention due to its potential applications in information progress and data storage. In this paper, monolayer Cr2S3 is proven to be a ferromagnetic (FM) semiconductor by using first-principles calculations. Moreover, monolayer Cr2S3 exhibits a perpendicular magnetic anisotropy energy of 30 μeV/f.u. Surprisingly, monolayer Cr2S3 presents spontaneous valley polarization, which means that it will be nonvolatile for data storage. Notably, monolayer Cr2S3 changes to an antiferromagnetic (AFM) state from the original FM state under biaxial tensile strain, and its easy axis will be reorientated from out-of-plane to in-plane when the compressive strain is larger than −2%. Importantly, for AFM monolayer Cr2S3, the valley polarization reversion can be realized by an external electric field along the z direction. In brief, valley polarization has been achieved in both FM and AFM monolayer Cr2S3, which is very rare in other valleytronics research. The present research provides a tantalizing candidate for realizing and manipulating valley and spin physics. [ABSTRACT FROM AUTHOR]

The mesogenic behavior and electronic properties of hydrogen bond ferroelectric liquid crystal (HBFLC) complex are studied using experimental and theoretical techniques. HBFLC complex is synthesized from mesogenic 4-hexyloxy benzoic acid (6O BA) as the proton donor and nonmesogenic chiral DL-tartaric acid (DLTA) as the proton acceptor through intermolecular hydrogen bonding. Molecular geometry of DLTA+6O BA HBFLC complex is optimized by density functional theory (DFT) calculation. An interesting observation is that polarizing optical microscope (POM) study confirms that the HBFLC complex exhibits thermochromic behavior in chiral nematic (N ∗) along with induced nontitled smectic G* phases. Another noteworthy observation is the manifestation of tripartite temperature stages. Fourier-transform infrared spectroscopy (FTIR) and natural bond orbital (NBO) analysis elucidate the intermolecular hydrogen bond between mesogenic (6O BA) and nonmesogenic (DLTA) compounds. Further, frontier molecular orbital (FMO) study and electrostatic potential (ESP) analysis explore the reactivity sites, intermolecular charge transfer and electronic behavior of HBFLC complex. [ABSTRACT FROM AUTHOR]

We report the synthesis and experimental studies on the liquid crystalline phase of a homologous series of compounds comprised of strongly asymmetric bent-core banana shaped molecules. Our x-ray diffraction studies clearly indicate that the compounds exhibit a frustrated tilted smectic phase with layer undulated structure. The low value of the dielectric constant as well as switching current measurements indicate the absence of polarization in this layer undulated phase. In spite of the absence of polarization, a planar aligned sample can be transformed irreversibly to a higher birefringent texture on the application of a high electric field. The zero field texture can only be retrieved by heating the sample to the isotropic phase and cooling it subsequently to the mesophase. We propose a double tilted smectic structure having layer undulation to account for the experimental observations with the layer undulation arising due to the leaning of the molecules in the layer. [ABSTRACT FROM AUTHOR]

The electro-optic coefficients of ferroelectric materials were obtained by Landau thermodynamic theory. It is proved that if the permittivity tensor is diagonal, then some ratios of the electro-optical coefficients are equal to the ratios of its diagonal components. The dependence of electro-optic coefficients on the external electric field for single-crystal barium titanate was studied and discussed. It is shown that electro-optic coefficients are rather high for barium titanate due to a non-linear response of dielectric susceptibility to electric field strength. [ABSTRACT FROM AUTHOR]

Dielectric properties of a ferroelectric liquid crystal 2-methylbutyl 4-decyloxybenzylidene-4'-n-aminocinnamate (DOBAMBC) confined in untreated and treated porous Anopore membrane were investigated depending on the frequency and temperature. The confinement of a ferroelectric liquid crystal in an untreated Anopore membrane leads to the disappearance of the Goldstone mode. Moreover, despite the modification of the pore surface with various surfactants, no the Goldstone mode or other additional relaxation processes were observed. The relaxation rate of the molecular δ-process is slightly shifted for untreated and treated Anopore membrane in comparison to the bulk. Generally, the relaxation rate temperature dependence shows the Arrhenius-type course, while for lecithin-treated Anopore, it is similar to the Vogel–Fulcher–Tammann-type dependence. Dielectric spectra are dominated at low frequencies by conductivity and electrode polarization effects and are modified in geometric constraints. [ABSTRACT FROM AUTHOR]

In this investigation, α -Fe2O3 was prepared via co-precipitation and nano-NiO and NdFeO3 were synthesized using the sol–gel method. For NdFe 0. 5 Ni 0. 5 O3 synthesis, Nd2O3, α -Fe2O3, and nano-NiO compounds were mixed via the solid state method. The effect of each component and that of nano-NiO on the NdFe 0. 5 Ni 0. 5 O3 crystal properties was characterized by using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible (UV–Vis), vibrating sample magnetometer (VSM), impedance and bandgap analyses. The orthorhombic perovskite structure was confirmed by the XRD data. With the doping of nano-NiO, the unit cell volume was found to decrease. The UV–Vis spectroscopy showed that the nano-NiO-doped optical bandgap ( E g ) had increased. The VSM analysis demonstrated that by doping nano-NiO to weak ferromagnetic NdFeO3, the resulting NdFe 0. 5 Ni 0. 5 O3 was rendered superparamagnetic. The real and imaginary parts of dielectric permittivity ( ′ and ″) and the loss tangent (tan δ) characteristic of the compounds were measured at AC-signaled frequencies of 100 Hz–10 MHz and a voltage range of 0–20 V DC. The increase in active charge transmission with the doping of nano-NiO reduced the ′ values. In addition, the large differences between the ′ values were thought to be caused by the breakdown voltage ( E b ) effect of the compounds. The ″ and tan δ changes revealed the dipole formation of the compounds at different voltages, their relaxation regions and their polarization mechanism type. The dielectric loss behavior of the compounds demonstrated their good dielectric material properties. This study investigated the effect of method difference and doped material particle size on magnetic and dielectric properties. [ABSTRACT FROM AUTHOR]

We clarified that a ferroelectric liquid crystal (FLC) has high resolution display capability as small as 1 × 1 μm pixel pitch using an FLC pixel array with a two‐layer electrode, which has a 1 × 1‐μm‐checkered apertured electrode and a plane electrode separated by an insulation layer. By applying +2 V to the apertured electrode and −10 V to the plane electrode in the two‐layer electrode and 0 V to the transparent common electrode, a checkered pattern was clearly observed, which indicates the successful individual pixel driving with a pixel pitch of 1 × 1 μm. When fabricating 1 × 2‐μm‐pitch rectangular FLC pixels, we elucidated that the liquid crystal alignment direction should be along the shorter side of the pixels to avoid asymmetric transmittance distribution in each pixel. Moreover, we successfully reconstructed a 3D holographic image using 10 × 10 k FLC pixel array with a pitch of 1 × 1 μm driven by the two‐layer electrode with hologram‐patterned apertures. We showed that FLC is a strong candidate material for realizing spatial light modulator with extremely small pixel pitches, which is essential for holographic displays with wide‐viewing‐zone angles. [ABSTRACT FROM AUTHOR]

In this investigation, α -Fe2O3 was prepared via co-precipitation and nano-NiO and NdFeO3 were synthesized using the sol–gel method. For NdFe 0. 5 Ni 0. 5 O3 synthesis, Nd2O3, α -Fe2O3, and nano-NiO compounds were mixed via the solid state method. The effect of each component and that of nano-NiO on the NdFe 0. 5 Ni 0. 5 O3 crystal properties was characterized by using X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX), ultraviolet-visible (UV–Vis), vibrating sample magnetometer (VSM), impedance and bandgap analyses. The orthorhombic perovskite structure was confirmed by the XRD data. With the doping of nano-NiO, the unit cell volume was found to decrease. The UV–Vis spectroscopy showed that the nano-NiO-doped optical bandgap ( E g ) had increased. The VSM analysis demonstrated that by doping nano-NiO to weak ferromagnetic NdFeO3, the resulting NdFe 0. 5 Ni 0. 5 O3 was rendered superparamagnetic. The real and imaginary parts of dielectric permittivity ( ′ and ″) and the loss tangent (tan δ) characteristic of the compounds were measured at AC-signaled frequencies of 100 Hz–10 MHz and a voltage range of 0–20 V DC. The increase in active charge transmission with the doping of nano-NiO reduced the ′ values. In addition, the large differences between the ′ values were thought to be caused by the breakdown voltage ( E b ) effect of the compounds. The ″ and tan δ changes revealed the dipole formation of the compounds at different voltages, their relaxation regions and their polarization mechanism type. The dielectric loss behavior of the compounds demonstrated their good dielectric material properties. This study investigated the effect of method difference and doped material particle size on magnetic and dielectric properties. [ABSTRACT FROM AUTHOR]

We achieve high‐framerate (< 100 μs) high‐contrast‐ratio ferroelectric liquid crystal displays (FLCD) on Gen 4.5. Innovatively, a new polyimide (PI) that is suitable for ferroelectric liquid crystal (FLC) alignment is synthesized and tested on the production line. It replaces Nylon 6 (N6), which was the barrier to the commercialization of FLCD. Moreover, a new FLC is synthesized to match requirements in mass production. Additionally, various materials were studied to investigate the surface energy and relative performance. It is not only proof of the feasibility on the production line, but also a significant step towards the commercialization of field‐sequential‐color high‐resolution FLCDs. [ABSTRACT FROM AUTHOR]

Usually, the resolution loss is serious in light field display due to the spatial multiplexing of several neighboring pixels to display images from different directions. With the limitation in the resolution of the flat panel display, the light field 3D display shows insufficient display size, image depth, or resolution. This article utilized the FLC with a fast response at 2 kHz and the optimized charge compensation method to achieve a high refresh time multiplexing method, which can effectively increase the display resolution by up to 32 times and is very promising for light field 3D displays in the future. [ABSTRACT FROM AUTHOR]

We developed a novel method for achieving long‐term (>24 hours) true bi‐stability in helix‐free Ferroelectric Liquid Crystals (FLCs). Instead of employing asymmetric boundary conditions, traditionally used for achieving bi‐stability, we utilized symmetric boundary conditions and carefully optimized the anchoring conditions on both the top and bottom substrates using the photoalignment technology. The key to the newly observed long term bi‐stability is the twisted alignment structure. Surface roughness was found to play a crucial role in achieving sustained bi‐stability. This breakthrough holds promise for developing truly bi‐stable, fast modulators for photonic applications. [ABSTRACT FROM AUTHOR]

Ferroelectric liquid crystals (FLCs) have two attractive characteristics: very fast switching speeds and stable alignment against electrical fringe fields from neighboring pixels. However, care needs to be taken because FLC panels can be prone to alignment defects caused by Chevron structures. At this time, we have succeeded in developing a new FLC which has an improved temperature range, with a wider SmC phase, and which is more stable, thus making it less likely to have alignment defects. We look forward to demonstrating this to you with LCOS panels containing this new FLC. [ABSTRACT FROM AUTHOR]

The first demonstration of converse piezoelectricity in 3D fluids is presented by measuring a linear electromechanical effect in ferroelectric nematic liquid crystals. The observed piezoelectric coupling constant below 6 kHz electric field is larger than 1 nC/N, comparable to, or better than, values for the strongest solid piezoelectric materials. Symmetry considerations indicate that the alignment of the ferroelectric nematic liquid crystal in the experimental study is not optimized, so the observed signal is likely only a fraction of the theoretically achievable signal. Understanding the electromechanical response of ferroelectric nematics will enable mechanical energy harvesting and open up a new avenue for developing fluid actuators, micro positioners, and electrically tunable optical lenses. [ABSTRACT FROM AUTHOR]

The synthesis and characterisation of 10 members of the [4[(E)-[4-[4-[ω-(4-cyanophenyl)phenoxy]alkyloxy]-3-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates is reported in which the number of methylene units in the flexible spacer is increased from three to twelve. The mesogenic units are based on cyanobiphenyl and 3-nitrobenzylideneaniline benzoate and linked by the spacer such that their dipoles are parallel giving rise to a large longitudinal dipole moment. All 10 members of the series show a nematic phase, and the nematic-isotropic transition temperatures, TNI, and associated entropy changes show a strong dependence on the length and parity of the spacer. This behaviour is attributed to the average shapes of the molecules and their flexibility. The heptyl member was further characterised using dielectric spectroscopy revealing a high value of dielectric permittivity reflecting the large dipole moment of the molecules and possibly indicating local short-range ferroelectric order. The synthesis and characterisation of two members of the [4[(E)-[4-[4-[3-(ω-cyanophenyl)phenoxy]alkyloxy]-4-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates are also described for which the difference in shape between odd and even members is reduced. Both dimers are exclusively nematogenic and the difference between TNI for the odd and even member is smaller reflecting the more similar molecular shapes. The potential for developing dimers that exhibit the ferroelectric nematic phase is discussed. [ABSTRACT FROM AUTHOR]

A nonlinear phenomenological model of flexoelectricity in thermoelastic solids is presented within the frame of continuum mechanics and extended thermodynamics, incorporating the quasi-electrostatic approximation where the time derivative of the electric displacement vector can be neglected in Maxwell–Ampère's law. An expression for the energy flux is proposed, including many internal variables. An advantage of the proposed model is that it presents a unified approach to study several thermo-electromechanical couplings, including electrostriction, piezoelectricity, dependence of entropy and spontaneous polarization on flexoelectricity, among others. The model may be of interest in revealing the effects of such couplings on the properties of polarizable media, in particular ferroelectrics, when simple boundary conditions prevail. For a fully dynamic description of flexoelectricity, Hamilton's principle and the variational principle for external forces should be used instead. [ABSTRACT FROM AUTHOR]

In this work, the impact of Ag–In–S quantum dots (QDs) on the dielectric and electro-optical characteristics of E7 nematic liquid crystal (NLC) is investigated. To realize the objective, various concentrations of Ag–In–S QDs (0.2, 0.4, 0.6, 0.8, and 1 wt%) were added to E7 NLC, and the resulting composites were then introduced into homogeneous, homeotropic, and twisted nematic aligned cells. The temperature dependence property of the parallel and perpendicular components of the dielectric constant (ɛ∥ & ε ⊥ ) for pure and QDs-doped NLCs was measured. ɛ∥ significantly enhanced in the presence of 0.8 wt% of the QDs, which led to a ~ 23% rise in the dielectric anisotropy of the system. The dielectric results demonstrated that NLC hosts prompt QDs to form self-assembled arrays within the NLC system. In addition, electro-optical measurements revealed the considerable impact of QDs doping on the reduction of threshold voltage (Vth). Importantly, a ~ 15% decrease in Vth was observed for NLC doped with 0.8 wt% of the QDs compared to pure NLC. Besides, the addition of QDs significantly accelerates the NLC electro-optical response. The switch-on and -off response times for the QDs-doped NLC cell were reduced by ~ 34% and ~ 41%, respectively, compared to those for the pure NLC cell. A combination of increased dielectric anisotropy, improved mutual interactions of components, and reduced rotational viscosity of the mixture may result in much faster electro-optical switching responses. The presented achievements in this study will be beneficial in the development of LC-based display panels as well as switchable smart windows. [ABSTRACT FROM AUTHOR]

Usually, the resolution loss is severe in light‐field display due to the spatial multiplexing of several neighboring pixels to display images from different directions. However, limited by the resolution of the flat panel display, the light‐field 3D display shows insufficient display size, 3D image depth, or resolution. This article uses optimized ferroelectric liquid crystal (FLC) shutters with high contrast (~1000:1), ultra‐fast response (<20 μs), and polarity‐related binary switching at low operating voltage (5 V). This article utilized 32 time‐sequentially opened FLC light valve arrays refreshed at 2 kHz to display images from different directions. Because of the polarity‐sensitive switching nature of FLC, the reverse phase induces serious crosstalk between different images. This work uses the timing synchronization method of dual‐FLC liquid crystal cells to achieve independent control of 32 light valves without reverse phase, reducing the crosstalk and increasing the equivalent 3D resolution by multiplexing the flat panel display 32 times within 60 Hz. [ABSTRACT FROM AUTHOR]

Recent experiments devoted to characterizing the behavior of sessile ferroelectric liquid droplets on ferroelectric solid substrates have shown the existence of a droplet electromechanical Rayleigh-like instability. The instability is induced by the bulk polarization of the ferroelectric fluid, which couples to the polarization of the underlying substrate through its fringing field and solid–fluid interface coupling. With the aim of characterizing this phenomenon, namely the coupling between the polarizations of a fluid and a solid material, we studied the behavior of ferroelectric liquid droplets confined between two solid substrates, arranged in different configurations, realized to generate fringing fields with different profiles. The results show that the features of the droplets instability are indeed affected by the specific fringing field shape in a way dominated by the minimization of the electrostatic energy associated with the bulk polarization of the ferroelectric fluid. [ABSTRACT FROM AUTHOR]

In light field displays, the resolution loss is a serious problem, leading to insufficient image depth, display size, and resolution. Here, we achieve a high refresh time multiplexing method that can effectively increase the display resolution by up to 32 times. Ferroelectric Liquid Crystal (FLC) with a fast response at 2 kHz and an optimized charge compensation method is proposed in this article. It is very promising for light field 3D displays in the future. [ABSTRACT FROM AUTHOR]

Optimized ODF machine for large scale display filled by ferroelectric liquid crystals (FLCs) is developed. Fast FLC filling at high temperature (100°C) in the vacuum, and sealing can automatically be done in one reaction pot. An uniform cell with good alignment quality and electro‐optical (E&O) performance are achieved which shows high contrast ratio (CR) =10000 :1 and a fast response time (33 μs) at room temperature, respectively. The realized FLC cell by ODF indicates that there are no mass production barriers for large scale FLC display. [ABSTRACT FROM AUTHOR]

A successful test of Ferroelectric Liquid Crystal Displays (FLCD) on Gen 4.5 is realized in this paper. A new polyimide (PI) that can replace Nylon 6 (N6) is synthesized and tested on the production line. This used to be the barrier in the commercialization of FLCD. Apart from that, a new FLC for mass production is synthesized. To investigate the surface energy and relative performance, various materials are compared. This proof of the feasibility on the production line is a significant step towards the commercialization of field‐sequential‐color high‐resolution FLCDs. [ABSTRACT FROM AUTHOR]

Since the discovery of the first ferroelectric liquid crystal (FLC) in the chiral smectic C (SmC*) phase, ferroelectricity in liquid crystals has attracted much attention due to not only the fundamental interest but also the applications. This review focuses on the evolution of the design concept for ferroelectric smectic liquid crystals. It progresses from considering macroscopic phase symmetry to designing intermolecular interactions. For the purpose of understanding the molecular organization in smectic phases, we propose a dynamic model of constituent molecules in the smectic A (SmA) and SmC* phases based on 13C NMR studies. Then, we follow the structure–property relationship in ferroelectric SmC* liquid crystals for FLC displays. We reconsider de Vries-like materials that can provide defect-free alignment. We pay attention to the electro-optical switching in the chiral de Vries smectic A phase. Finally, we show several liquid crystals exhibiting polar smectic A phases and discuss how the polar order occurs in the highest symmetric smectic A phase. [ABSTRACT FROM AUTHOR]

Ferroelectric nematic liquid crystals are formed by achiral molecules with large dipole moments. Their three-dimensional orientational order is described as unidirectionally polar. We demonstrate that the ground state of a flat slab of a ferroelectric nematic unconstrained by externally imposed alignment directions is chiral, with left- and right-handed twists of polarization. Although the helicoidal deformations and defect walls that separate domains of opposite handedness increase the elastic energy, the twists reduce the electrostatic energy and become weaker when the material is doped with ions. This work shows that the polar orientational order of molecules could trigger chirality in soft matter with no chemically induced chiral centers. [ABSTRACT FROM AUTHOR]

Freestanding slender fluid filaments of room‐temperature ferroelectric nematic liquid crystals are described. They are stabilized either by internal electric fields of bound charges formed due to polarization splay or by external voltage applied between suspending wires. The phenomenon is similar to those observed in dielectric fluids, such as deionized water, except that in ferroelectric nematic materials the voltages required are three orders of magnitudes smaller and the aspect ratio is much higher. The observed ferroelectric fluid threads are not only unique and novel but also offer measurements of basic physical quantities, such as the ferroelectric polarization and viscosity. Ferroelectric nematic fluid threads may have practical applications in nano‐fluidic micron‐size logic devices, switches, and relays. [ABSTRACT FROM AUTHOR]

Tunable optical lenses are in great demand in modern technologies ranging from augmented and virtual reality to sensing and detection. In this work, electrically tunable microlenses based on a polymer‐stabilized chiral ferroelectric nematic liquid crystal are described. The power of the lens can be quickly (within 5 ms) varied by ≈500 diopters by ramping an in‐plane electric field from 0 to 2.5 V µm−1. Importantly, within this relatively low‐amplitude field range, the lens is optically isotropic; thus, its focal length is independent of the polarization of incoming light. This remarkable performance combines the advantages of electrically tuned isotropic lenses and the field‐controlled shape of the lens, which are unique properties of chiral ferroelectric nematic liquid crystals and have no counterpart in other liquid crystals. The achieved lens performance represents a significant step forward as compared to liquid lenses controlled by electrowetting and opens new possibilities in various applications such as biomimetic optics, security printing, and solar energy concentration. [ABSTRACT FROM AUTHOR]

The ferroelectric liquid crystals (FLC) composites with improved electro-optic properties, obtained by incorporating CdSe (CS) nanoplatelets (NPLs), are reported. Noticeable improvementin optical contrast, saturation voltage, response time, and brightness of FLC have been found. The improvements of electro-optical properties are the results of enhanced molecular alignment of FLC due to the presence of CS NPLs. Time resolved photoluminescence (TRPL) measurements reveal NPLs surface energy transfer in FLC. Two types of Fӧrster resonant energy transfer (FRET) is observed in CS incorporated FLC. First is homo FRET which is the transfer of exciton within stacked CS NPLs and second is FRET between FLC and CS NPLs. FRET are supporting the CS incorporated FLC to get superior electro-optic properties. These findings may create opportunity of future CS NPLs incorporated FLC based display devices having better electro-optical properties. [ABSTRACT FROM AUTHOR]

The discovery of polar liquid crystals, such as ferroelectric and helielectric liquid crystals, provides fascinating platforms for designing and modulating polarisation structures that generate strong second harmonic generation. Here, we report that the helielectric nematics, i.e. the polar cholesteric liquid crystals, realise an unprecedented phase-matching condition for the second harmonic generation in the photonic bandgap. Like the circular dichroism in the linear optical regime, the phase-matched second harmonic generation generated in a helielectric nematic medium exhibits a circular polarisation selectivity in the nonlinear optical regime. The maximum g-factor for the second harmonic generation is over ~ 1.95. [ABSTRACT FROM AUTHOR]

The huge dielectric constant of ferroelectric nematic liquid crystals (FNLCs) seems to bring about a difficulty of molecular alignment control in exchange for a potential device application. To obtain a satisfactory level of uniform molecular alignment, it is essential to understand how the molecules near the alignment surface are anchored. In this study, bulk molecular alignment with an anti-parallel rubbing manner, which has not yet been investigated extensively, is explained using a conventional torque balance model introducing a polar anchoring function, and it is shown that the disappearance of the bulk twist alignment with decreasing cell thickness can be explained self-consistently. To validate this estimation for a room-temperature FNLC substance, the Brewster angle reflection method was attempted to confirm the surface director's deviation from the rubbing direction caused by the polar surface anchoring. [ABSTRACT FROM AUTHOR]

Bio-waste-based porous carbon nanoparticles (PCNPs) were synthesized using green synthesis and investigated their doping effect on the optical and electrical properties of polymer-dispersed ferroelectric liquid crystals (PDFLCs) composites. Here we employed the polymerization-induced phase separation (PIPS) approach for constructing the PDFLCs. Our results indicate that the dispersion of PCNPs into the PDFLC material results in an alteration to several physical parameters, including morphology, dielectric permittivity, conductivity and optical band gap. A decrease in the ac conductivity of the doped samples was seen. Additionally, UV-Visible study reveals that inclusion of PCNPs resulted in a decrease in the optical band gap of PDFLC, with a value of approximately 3.1 eV. These findings demonstrate the potential of using PCNPs as dopants in PDFLCs for various applications, including sensing, energy storage and optoelectronics. [ABSTRACT FROM AUTHOR]

Ferroelectric liquid crystals(FLCs), an exciting class of liquid crystals(LCs), found potential applications in the display as well as non-display regimes due to their fast response, low driving voltage and nonvolatile memory. The amalgamation of nanoparticles into FLCs has opened up new avenues in the LCs research field by alterations/modification of the existing properties of LCs. In this work, porous carbon nanoparticles (PCNPs) were dispersed into FLC mixture (W206E) and investigated their doping effect on FLC's textural, phase transition temperatures and dielectric studies in planar-aligned cells. Dielectric spectroscopy was carried out in the frequency range of 20 Hz to 10 MHz to explore the frequency as well as the temperature dependent of FLC in the entire SmC* region. The transition temperature of FLC mixture is increased by 4 °C in PCNPs doped FLC sample then undoped FLC sample. Nearly 8.42% increase in permittivity is observed. A Gold stone relaxation mode at ∼627 Hz was observed at lower frequency. [ABSTRACT FROM AUTHOR]

High-tilt angle ferroelectric liquid crystal material in surface stabilised geometry (SSFLC) is investigated for the smectic layer reorientation and its molecular dynamics by electro-optical and dielectric spectroscopy techniques. Smectic layer reorientation (5 $^o$ o to 45 $^o$ o ) is obtained by controlled cooling rate and applying electric field in the vicinity of transition temperature from chiral nematic (${N^*}$ N ∗ ) to chiral smectic C ($Sm{C^*}$ Sm C ∗ ) phase. After slow cooling down to room temperature, the stripe domain textures along the rubbing are observed with quasi-bistable states. Dielectric spectroscopy has revealed the unusual increment in the dielectric permittivity. A dielectric relaxation process at lower frequency than Goldstone mode with the increase in DC bias up to 2 $V$ V is observed in the sample cooled without any bias. This increment is found to be originated by the heliconical structure within the stripes which is seen in the optical textures recorded at the time of dielectric scan. However, this increment is not observed in the sample cooled under DC bias. Thus, there exist different phenomena in the high tilt angle SSFLC sample cooled in different conditions of DC bias; stripe domains, smectic layers reorientation, heliconical stricture and twisted structure within stripes which are significant to explore deeply in high-tilt angle ferroelectric liquid crystals. [ABSTRACT FROM AUTHOR]

KCFLC 7S, a ferroelectric liquid crystal (FLC) shows improved dielectric and electro-optic properties by the incorporation of alloyed quaternary ZnCuGaS2/ZnS core/shell (ZCZ) quantum dots (QDs). Four different Zn alloyed ZCZ QDs (ZCZ-0, ZCZ-0.5, ZCZ-1, and ZCZ-1.5) incorporated in FLC and have been studied with the help of optical, dielectric and ferroelectric characterisations. Substantial changes of optical contrast, molecular ordering, photoluminescence, dielectric constant, dielectric loss factor, response time, and helical pitch of FLC are observed and attributed to varying molecular ordering. The effective confinement of exciton wavefunction in core of QDs results in improved molecular ordering of FLC material. The Zn alloyed ZCZ QDs incorporated FLC may be resulted for future brighter, high contrast, large viewing angle and memory based display device. [ABSTRACT FROM AUTHOR]

The properties of ferroelectric liquid crystal (FLC) in the mixtures of FLC and quantum dots have been studied. The theory is modelled with well-known Flory–Huggins theory and Landau theory. The effect quantum dots concentrations and temperature on the pitch length, spontaneous polarisation and tilt angle in the chiral smectic-C* phase of the smectic-A to chiral smectic-C* transition has been discussed. Theoretical analysis shows the increase of the pitch length, spontaneous polarisation and tilt angle with the increase of concentrations of quantum dots in the quantum dots-doped FLC system.A qualitativee comparison between theoretical and experimental results has been discussed. [ABSTRACT FROM AUTHOR]

In the present work one biphenyl benzoate cored liquid crystal was characterized using geometrical optimization and electro-optic study. Geometry of the molecule was optimized using Hartree-Fock method with 3-21G basis. The simulated value of molecular length and dipole moment was reported. The Infrared (IR) spectra were also simulated and analyzed. The energy gap between highest occupied molecular orbit (HOMO) and lowest unoccupied molecular orbit (LUMO) was calculated. The phase transition temperatures and phase sequences were identified by observing the topological defects in the optical textures at different temperatures under polarizing microscope. It exhibited ferroelectric smectics C* (SmC*) phase for a wide range of temperature and then directly melted into isotropic phase. The optical tilt angle of the compound was measured in SmC* phase and was fitted with mean field model to explore the nature of phase transition. The applicability of the compound for display applications were judged based on the parameters measured. [ABSTRACT FROM AUTHOR]

Extensive research has been devoted to spiral phase contrast imaging because of its notable capacity to enhance the edges of both phase and amplitude objects. We demonstrate a setup using ferroelectric liquid crystal (FLC) fork grating (FG) to enable switchable spiral phase contrast imaging within sub-milli-second responses. This system enables the electrical toggling between images featuring edge enhancement and those without it. The specially designed FLC FG generates a vortex beam while in a diffractive state and transmits a Gaussian beam when in a transmissive state. Using a two-step photo-alignment method, the produced FLC FG exhibits exceptional efficiency at approximately 35% and impressively rapid switching at around 307 μs. By introducing this method, we expand the potential applications of spiral phase contrast imaging, particularly in fields such as bio-sensing and photonics. [ABSTRACT FROM AUTHOR]

The study demonstrates high‐quality pulsed‐laser‐deposited (PLD) barium titanate (BTO) thin‐films on a magnesium oxide substrate. The frequency response of the relative permittivity (dielectric constant) and the linear electro‐optical coefficient (Pockels coefficient) are measured. At 0.2 GHz, the Pockels coefficient is fitted to be r42 ≈ 1030 pm V−1. It decreases to ≈390 pm V−1 at 10 GHz after which it remains constant up to 70 GHz. The unbiased BTO permittivity is measured to be εa ≈ 7600 at 0.2 GHz, dropping to ≈1100 at 67 GHz, while the biased BTO had a permittivity εa ≈ 2000 at 0.2 GHz, dropping to ≈500 at 67 GHz. These results fill an important experimental characterization gap for high‐speed BTO applications and show the high quality of PLD‐grown BTO films. Lastly, the material's crystalline quality is characterized and the domain distribution is imaged. The findings enable the design and fabrication of a new generation of BTO‐based components for sensing and communications. [ABSTRACT FROM AUTHOR]

We represent a detailed study of a dilute suspension of ferroelectric barium titanate nanoparticles (BaTiO3 NPs) in a nematic matrix by probing dielectric, electro-optical, and optical properties. The strong local surface electric field (order of ~1010 Vm-1) of BaTiO3 produces pseudonematic domains within the matrix, which renders an enhancement in both the perpendicular and parallel components of dielectric permittivity that increases with increasing NP concentrations. Due to changes in molecular ordering, the dielectric anisotropy of pristine nematic increases by 10.7%, 24.6%, and 33.3% after the addition of 0.1, 0.3, and 0.5 wt. % BaTiO3 NPs with subsequent lowering in threshold voltage. Interestingly, the nematic-BaTiO3 blended cells showed 23.2%, 49.3% and 67.6% faster electro-optic response for 0.1, 0.3, and 0.5 wt. % of NPs, respectively. In the nematic matrix, BaTiO3 NPs act like chromophores resulting in a bathochromic shift in fluorescence spectra due to an enhanced degree of conjugation. This investigation reveals that the ferroelectric BaTiO3 NPs-nematic composites will be suitable for superior fluorescent electro-optical devices. [ABSTRACT FROM AUTHOR]

The molecular properties of a biphenyl benzoate based ferroelectric liquid crystal compound were estimated using DFT/6-31G method. Non Linear Optical properties of the compound have been estimated by calculating its polarizability and hyperpolarizability. Frontier molecular orbital (FMO), Molecular electrostatic potential (MEP) and Infrared (IR) spectra have been simulated. Global parameter and a few thermodynamic parameters have also been calculated. The phase sequence has been confirmed by polarizing optical microscopy. The spontaneous polarization and rotational viscosity of the compound have been measured. From results the efficacy of the compound in NLO or electro optical applications have been inferred. [ABSTRACT FROM AUTHOR]

The problem of formation a reproducible spatially-uniform alignment of smectic С* ferroelectric liquid crystals (FLCs) in liquid-crystal (LC) cells has not been completely solved yet. We investigated aligning layers (anisotropic coatings) of different types (island and continuous). These layers contact with FLC in LC cells and form a selected direction for molecular orientation. It was investigated the influence of mechanical cycles numbers of rubbing polymer alignment layers made of polyvinyl alcohol and polyamide 66 on the optical quality of FLC cells to which electric field was not applied. It is shown that there is an optimal number of rubbing cycles for obtaining the best optical quality of FLC cells; the number of cycles is individual for each polymer alignment layer and coating type. [ABSTRACT FROM AUTHOR]

In this paper, the refractive index and extinction coefficient of ferroelectric liquid crystals have been examined by the terahertz time-domain spectroscopy system. Two modes of ferroelectric liquid crystal materials, deformed helix ferroelectric liquid crystal (DHFLC), and electric suppressed helix ferroelectric liquid crystal (ESHFLC) are tested as experimental samples. Nematic liquid crystal (NLC) was also investigated for comparison. The birefringence of DHFLC 587 slowly increases with the growth of frequency, and it averages at 0.115. Its extinction coefficients gradually incline to their stable states at 0.06 for o-wave and 0.04 for e-wave. The birefringence of ESHFLC FD4004N remains between around 0.165 and 0.175, and both of its e-wave and o-wave extinction coefficients are under 0.1, ranging from 0.05 to 0.09. These results of FLC will facilitate the examination and improve the response performance of THz devices using fast liquid crystal materials. [ABSTRACT FROM AUTHOR]

Complex structure formation inside or through turbid media is a challenging task due to refractive index inhomogeneity, random light scattering, and speckle noise formation. In this article, we have coupled the data regression model in the R-squared metric and used its advantages as a fitness function in the genetic algorithm to advance the resolution and structural uniformity. As a compatible system with the binary genetic algorithm, we have presented a cost-effective iterative wavefront shaping system-design with binary phase modulation using an affordable ferroelectric liquid crystal (FLC) based binary-phase spatial light modulator (SLM). R-squared metric in the genetic algorithm is analyzed to optimize the binary phase mask, and the prototype system based on iterative binary phase modulation has been validated with a 120-grit ground glass diffuser and fresh chicken tissues of thickness 307 μ m and 812 μ m . The detailed results show that the proposed cost-effective wavefront shaping system with data regression model assisted R-squared fitness function can construct high-resolution multiple complex hetero-structures simultaneously in 3D volume using an optimized single phase-mask. [ABSTRACT FROM AUTHOR]

The chiral smectic-C to smectic-C (SmC *-SmC) phase transition has been studied using dynamic renormalization group (DRG) analysis. Langevin equations are derived from the nonlinear elastic model of the SmC *-SmC phase transition. The DRG equations are derived. The DRG analysis predicts the Kosterlitz-Thouless transition at low frequency limit and Kardar-Parisi-Zhang (KPZ) fixed point. The DRG calculation confirms that the SmC*-SmC phase transition belong to the KPZ universality class. [ABSTRACT FROM AUTHOR]

The effect of graphene nanoparticles on the smectic-C* to smectic-C*A (SmC* to SmC*A) phase transition in antiferroelectric liquid crystal is studied theoretically. Model free energy is based on Flory-Huggins free energy of isotropic mixing and Landau theory of phase transition. The effect of graphene nanoparticles concentration on tilt angle, spontaneous polarization and dielectric susceptibility in the smectic-C*A phase of the SmC* to SmC*A phase transition has been studied extensively. The qualitative agreement between theoretical and experimental results is found. [ABSTRACT FROM AUTHOR]

This article presents an approach to achieve a fast and analog geometrical phase modulation based on the optical axis rotation of the defect‐free Deformed Helix Ferroelectric Liquid Crystal (DHFLC) with a short pitch. This study demonstrates a Spatial Light Modulator (SLM) prototype with a feature size of 3 µm without Fringe Field Effect (FFE), having a phase depth of 1.9π, fast switching time (<250 µs) at a low operating voltage (<7 V), and high diffraction efficiency (>77%). The high phase modulation depth is achieved by developing DHFLC with a cone angle of up to 85˚, which is inherently immune to FFE. The ellipticity is minimized by using a compensation film that can suppress the changes in birefringence under the applied electric field. The proposed SLM is promising in applications such as a real‐time hologram and dynamic beam steering in Light Ranging and Detector (LiDAR). [ABSTRACT FROM AUTHOR]