Solid polymer electrolytes (SPEs) offer a compelling path toward next-generation all-solid-state batteries (ASSBs), but their practical application remains constrained by low ionic conductivity and poor interfacial stability. These limitations arise from the intrinsically low dielectric constant of polymer matrices that fail to effectively dissociate lithium salts. Meanwhile, the disordered ion pathways induce tortuous migration routes and nonuniform current density at electrode interfaces. This perspective introduces the concept of programming ionic transport, which integrates ferroelectric liquid crystals (LCs), dielectric field engineering, and process-programmed assembly to overcome these challenges. Ferroelectric LCs offer a unique combination of high dielectric anisotropy and programmable molecular order, enabling the creation of low-tortuosity ion highways with built-in polarization fields. The spontaneous polarization of ferroelectric nematic phases can generate local electric fields that actively repel anions and guide lithium ions, potentially overcoming the limitations of conventional SPEs. To translate this molecular order into macroscopic device function, we highlight the critical role of advanced manufacturing techniques. Process-programmed assembly, including shear-induced alignment in 3D printing and electrospinning, provides a direct means to control alignment of LCs into designed architectures. The integration of material design and digital fabrication enables electrolytes with graded dielectric properties, hierarchical ion transport networks, and customized device geometries for ASSBs. We outline a roadmap for the future development of ASSBs that moves beyond facilitated ion transport toward actively programmed ion transport.

ABSTRACT With the rise of the “metaverse” concept, 3D display technologies that deliver strong presence and immersion, are attracting increasing attention. Among them, holographic 3D displays are regarded as one of the most promising solutions, because they directly reconstruct the complete wavefront of a 3D light field and provide all depth cues to the human eye, including vergence‐accommodation. This review systematically summarizes recent advances in liquid crystal (LC)‐based holographic 3D displays from the perspectives of materials systems and device architectures. It concentrates on LC devices that leverage the intrinsic optical anisotropy, programmable alignment and their field‐tunable properties, covering chiral structured LC devices, LC polarization elements, LC metasurfaces, and other representative LC optical components. Their roles in holographic wavefront modulation and ultra‐thin holographic optical elements (HOEs) are highlighted. This review also discusses the opportunities and challenges of cascaded multilayer LC devices for multidimensional, programmable wavefront control and high‐capacity holographic displays. Overall, this review provides a systematic reference for the design, optimization, and integration of LC‐related materials and devices, and offers insights into next‐generation holographic 3D display systems with immersive and visually comfortable performance.

ABSTRACT Chiral liquid crystals (CLCs) are widely explored for polarization‐selective photonic applications due to their photonic bandgap and strong Bragg reflection, yet a predictive framework linking bulk eigenmodes to external wave propagation remains underdeveloped. Here, we introduce a Floquet‐based theoretical framework that rigorously describes electromagnetic eigenstates in periodic helicoidal media and establishes a direct mapping between bulk 3D modes and their emission into external media. This approach enables quantitative prediction of key optical phenomena, including Bragg reflection, total internal reflection, and polarization‐selective mode routing, in both planar and tilted CLC configurations. We experimentally validate these predictions through angular‐resolved measurements, demonstrating excellent agreement with theory. Beyond visualization of dispersion relations, our framework provides a unified and predictive tool to engineer light transport in chiral photonic media. These results establish a predictive design framework for cholesteric photonic devices and highlight their potential for advanced diffractive optics, including emerging AR/XR applications.

This research addresses the challenge of controlling complex director fields in confined chiral liquid crystal (CLC) geometries. CLC droplets were inkjet-printed onto high-resolution photoalignment patterns to study the competition among chiral pitch, geometric confinement, and surface-alignment periodicity. Polarized microscopy analysis and conceptual 3D modeling reveal that surface photoalignment dictates the droplet structure, steering the director field independently of the curved droplet's profile. Findings show that at small periods Λ, surface anchoring suppresses domain curvature in favour of a well-defined 1D director lattice. This transition confirms that photoalignment can either enforce directional orientation or allow curvilinear fields depending on the confinement.

The growing demand for holography and its wide-ranging applications necessitate advancements to make this technology more accessible and adaptable to modern technological requirements. Nematic liquid crystals (NLCs) enable holographic projection by exploiting the geometric phase of light through carefully designed phase patterns. However, NLC-based holography faces challenges, particularly in terms of projection quality and the presence of zero-order leakage-a bright spot that overlaps the reconstructed image. The efficiency of the reconstructed image is strictly related to the thickness of the NLC layer, which is challenging to control with high precision. In this work, we use chiral liquid crystal (CLC) to fabricate reflective holograms. To address the issue of leakage waves overlapping the reconstructed image, we propose an interference-based fabrication approach. This approach combines the phase pattern of the hologram with a diffraction grating by interfering a plane wave with a tailored wavefront precisely matching the hologram's phase pattern. As a result, the image is reconstructed away from the zero-order reflection, and the leakage overlapping with the reconstructed image is reduced significantly.

Starting from our previously proposed line element and considering more “surface color” datasets, we derive a simplified version which matches experimental datasets equally well and resulted into a conformally-Euclidean line element, which is conceptually much simpler than any existing color difference metrics. The color difference is written as an Euclidean difference multiplied with a simple factor which depends on the luminance only. In a subspace with constant luminance, as considered by MacAdam, this factor becomes constant and the subspace is flat. The same holds for sufficiently large luminances. Based on this LE we derive perceptual coordinates (A,l_c,s_c) very similar to the CIELab (L^*,a^*,b^*).

ABSTRACT Liquid crystal (LC) photoalignment and photopatterning provide versatile, non‐contact approaches for encoding spatially varying molecular orientation, enabling compact, flat, and reconfigurable optical elements for structured light generation. This review summarizes recent advances in photoalignment strategies and patterned LC architectures that directly tailor optical phase, polarization, and amplitude, therefore producing a wide range of structured beams and wavefronts. We cover multiple LC phases including nematic, chiral nematic, blue phase (BP), and ferroelectric nematic (N F ) systems. Emphasis is placed on the translation from photoaligned LC director patterns to core structured‐light functionalities, including geometric‐phase modulation, and vector beams (VBs), orbital angular momentum (OAM) mode generation, as well as beam steering, lattice formation and intensity‐profile shaping. By explicitly linking fabrication routes and patterning fidelity to structured light metrics, this review establishes a unified framework for the rational design of photoaligned LC photonic systems and identifies pathways toward scalable manufacturing. We further discuss emerging LC‐enabled opportunities for quantum structured light and quantum information processing, and outline promising research directions at the intersection of advanced LC materials and integrated photonics.

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.

Structured light features spatially or temporally modulated amplitude, phase, or polarization. It supports high-dimensional encoding for optical communication and enables new capabilities in quantum communication. However, conventional isotropic optics often cannot generate or process these fields efficiently because they do not provide the required spatially varying anisotropy. Liquid crystals (LCs) address this limitation by combining long-range orientational order with reconfigurable control of optical anisotropy through engineered molecular alignment. This perspective summarizes two complementary implementation strategies. Photopatterned alignment in LC cells offers high-resolution beam shaping and can be combined with electrical driving for tunable operation. Crystallization-assisted locking permanently fixes a designed molecular configuration and provides robust, long-term performance. Together, these strategies offer compact and practical pathways for generating, modulating, and multiplexing structured light. Applications prioritizing long-term stability generally benefit from structural locking.

With nematic liquid crystal (LC) topological defects can be created that are important for the generation of laser beams with orbital angular momentum. Arrays of defects have been realized through photoalignment, by projecting images of a spatial light modulator or digital mirror device. However, such pixel-based approaches seriously limit the achievable density of defects. Here, we propose a scalable method based on two-step interference illumination to achieve a much higher density. In the first step, a rotating director pattern is generated by the interference of two circularly polarized beams. In the second step, amplitude modulation by two-beam interference is used to rewrite the pattern and introduce the defects. By adjusting the illumination doses and angles of incidence in both steps, 2D defect patterns are obtained, with spacing down to 1.25 micrometer. The resulting disclination lines are analyzed, and the proposed structure is supported by numerical simulations. For the first time, a high defect density defect grid is obtained through a scalable two-step photoalignment procedure. This approach enables optical components with large-angle diffraction and bridges the gap between LC topological optics and metasurfaces.

The development of all-solid-state batteries (ASSBs) is critical for overcoming the safety and performance limitations of conventional lithium-ion batteries with liquid electrolytes. Solid polymer electrolytes (SPEs) offer promising processability and interfacial contact but suffer from low room-temperature ionic conductivity. Liquid crystal electrolytes (LCEs) have emerged as a solution, leveraging their self-assembling mesophases to create ordered ion transport channels that enhance conductivity. However, translating the molecular advantages of LCEs into high-performance devices requires advanced manufacturing techniques capable of precise structural control. This work introduces a novel 3D-printed, ultra-thin (20 µm) composite LCE membrane engineered for high dielectric constant (εr' ∼ 40) and ionic conductivity (~10-3 S cm-1). The membrane is composed of a polymer matrix (PVDF), a polymer network formed by the reaction of liquid crystal (LC) monomer RM257 and thiol monomers, and the high-dielectric small molecule LC 4-cyano-4'-pentylbiphenyl (5CB). When integrated into ASSBs with a lithium metal anode and LiCoO2 cathode, the printed LCE membrane enables outstanding long-term cycling stability (retaining a capacity of 76.6% over 3000 cycles). This study demonstrates that combining molecular design with additive manufacturing provides a powerful strategy for developing high-performance, durable, and safe ASSBs.

Chiral liquid crystal forms a helical structure and when the pitch in the range of visible light, efficient Bragg reflection can occur. In combination with patterned photoalignment, the diffractive reflection can be steered in an arbitrary direction with high efficiency (>90%). This approach can be used in many applications, such as augmented reality, compact spectrometers or asymmetric reflectors.

We developed a new Riemannian color difference metric for static spatial sinusoidal color variations. With this metric, one can predict, in any direction of the color space, the detection threshold of sinusoidal color variations. The metric includes the angular size, spatial frequency, luminance, and chromaticity of the grating. The metric is based on the Riemannian color difference metric for split fields that we developed earlier and models for contrast sensitivity functions of the isolated achromatic, red-green, and blue-yellow detection mechanisms. We validated the models of the contrast sensitivity functions against various datasets. The color difference metric was validated against datasets of isoluminous chromatic Gabor gratings at various spatial frequencies and various color centers. We found adequate agreement with these datasets. The results are presented in the CIELAB (a & lowast;,b & lowast;)$$ \left({a}<^>{\ast },{b}<^>{\ast}\right) $$ plane.

Liquid Crystal Waveguiding A layer of nematic liquid crystal forms a complex three-dimensional structure on top of a substrate with patterned alignment, to minimize the total free energy. Roughly in the middle of the layer, there is a region where the director is perpendicular to the substrates, forming a multimode waveguide for TE polarized light. The figure illustrates how a green laser beam follows the curved waveguide formed by the patterned liquid crystal. More details can be found in article 2402174 by Kristiaan Neyts and co-workers.

Optical trapping of small particles with laser light is a versatile method for manipulation. In this work two laser trapping experiments are described. In the first experiment the charge of a trapped particle in water is measured with the resolution of the elementary charge, by measuring the displacement in an electric field. An ac electric field is used to exert a sinusoidal force onto the particle, and the amplitude of the oscillation is measured with a quadrant photodetector. This setup has extended the limits of sensitivity, which allows to see discrete steps in the charge of the nanoparticles, even in a highly polar material such as water. In the second experiment micrometer size particles consisting of polymerized chiral liquid crystal start spinning under influence of the polarization of the laser trapping beam. This work consists of experimental results, showing the period of the rotation as a function of the polarization of the laser beam, and simulation results, in which the torque exerted by the laser beam on the chiral particle is calculated. It is observed that some particles can be rotated in both directions when the degree of circular polarization is sufficiently high, while other particles only rotate in one direction.

Chiral liquid crystals spontaneously arrange into a helical structure of which the pitch depends on the concentration of the chiral dopant. If the effective wavelength inside the liquid crystal matches the period of the helix, Bragg reflection occurs and light is efficiently reflected. A periodic photoalignment pattern at the surface of a substrate can be used to tilt the axis of the helical structure and redirect the reflected light into a desired direction. This principle is used in waveguide-based beam combiners for augmented reality devices and in single component spectrometers.

All-solid-state batteries (ASSBs) are widely regarded as one of the most promising candidates for next-generation energy storage technologies. Among the various components of ASSBs, solid polymer electrolytes (SPEs) have attracted significant attention due to their excellent mechanical toughness, low densities, ease of processing, and good interfacial contact with electrodes. In recent years, liquid crystal polymer (LCP) electrolytes have emerged as a research hotspot. Unlike traditional classifications of dielectric and non-dielectric phases, the unique ordered self-assembled structures of LCP electrolytes can provide highly efficient ion transport pathways. This perspective presents a systematic perspective on regulating the performance of lithium-ion batteries (LIBs) (especially ASSBs) through the synergistic combination of dielectric and liquid crystal (LC) phases. The aim of this work is to offer detailed and timely insight into the advantages and disadvantages of polymers and their composite electrolytes from the perspectives of dielectric and ferroelectric phases, while also evaluating the potential of LCPs from the viewpoints of LC and non-LC phases. By combining the advantages of dielectric and LC phases, this work envisions a future for SPEs where ferroelectric LCPs and their composites emerge as a new class of SPEs.