Liquid crystal microwave phased arrays (LC-MPAs) are regarded as an ideal approach to realize compact antennas owing to their advantages in cost, size, weight, and power consumption. However, the shortcoming in low radiation deflection efficiency has been one of LC-MPAs’ main application limitations. To optimize the steering performance of LC-MPAs, it is essential to model the channel imperfections and compensate for the phase errors. In this paper, a phase error estimation model is built by training a neural network to establish a nonlinear relationship between the near-field phase error and the far-field pattern, hence realizing fast calibration for LC-MPAs within several measured patterns. Simulations and experiments on a 64-channel, two-dimensional planar antenna were conducted to validate this method. The results show that this method offers precise phase error estimations of 3.58° on average, realizes a fast calibration process with several field-measured radiation patterns, and improves the performances of the LC-MPA by approximately 4%–10% in deflection efficiency at different steering angles.

In this paper, the feasibility of a high laser damage threshold liquid crystal spatial light modulator based on gallium nitride (GaN) transparent conductive electrodes is proved. The laser-induced damage threshold (LIDT) is measured, and a high LIDT reflective optically addressed liquid crystal light valve (OALCLV) based on GaN is designed and fabricated. The proper work mode of the OALCLV is determined; the OALCLV obtained a maximum reflectivity of about 55% and an on–off ratio of 55:1, and an image response is demonstrated.

In this paper, we propose an effective method to compensate for the performance degradation of optically addressed spatial light modulators (OASLMs). The thermal deposition problem usually leads to the on-off ratio reduction of amplitude OASLM, so it is difficult to achieve better results in high-power laser systems. Through the analysis of the laser-induced temperature rise model and the liquid crystal layer voltage model, it is found that reducing the driving voltage of the liquid crystal light valve and increasing the driving current of the optical writing module can compensate for the decrease of on–off ratio caused by temperature rise. This is the result of effectively utilizing the photoconductive effect of Bi12SiO20 (BSO) crystal. The experimental results verify the feasibility of the proposed method and increase the laser withstand power of amplitude-only OASLM by about a factor of 2.5.

In order to improve the damage threshold and enlarge the aperture of a laser beam shaper, photolithographic patterning technology is adopted to design a new type of liquid crystal binary mask. The inherent conductive metal layer of commercial liquid crystal electro-optical spatial light modulators is replaced by azobenzene-based photoalignment layers patterned by noncontact photolithography. Using the azobenzene-based photoalignment layer, a liquid crystal binary mask for beam shaping is fabricated. In addition, the shaping ability, damage threshold, write/erase flexibility and stability of the liquid crystal binary mask are tested. Using a 1 Hz near-IR (1064 nm) laser, the multiple-shot nanosecond damage threshold of the liquid crystal mask is measured to be higher than $15~\text{J}/\text{cm}^{2}$. The damage threshold of the azobenzene-based photoalignment layer is higher than $50~\text{J}/\text{cm}^{2}$ under the same testing conditions.

In recent decades, increasing research interest has shifted from traditional rigid skeleton robotics to flexible, shape-programmable, environmentally adaptive and stimuli-responsive “soft robotics”. Within this discipline, soft-robots capable of untethered and/or remote-controlled operation are of particular interest given their utility for actuation in complex situations with larger range of mobility and higher degrees of freedom. The use of new materials and the development of advanced fabrication techniques enable better performance and expand the utility of such soft actuators, moving them towards real-world applications. This review outlines some recent advances in untethered soft robotics and actuators to illustrate the promise of these applications at the interface of material science and device engineering.

Multifunctionality was created by coupling an electronic charge carrier transport with ionic conductivity or ferroelectricity in polarized liquid crystal phases. Liquid-crystalline perylene bisimide derivatives bearing cyclotetrasiloxane rings and triethylene oxide chains formed nanosegregated columnar structures which could conduct ions as well as electrons. The spin-coated thin films could be insolubilized by the exposure on acid vapors and display electrochromism. Phenylterthiophene derivatives bearing a chiral alkyl side chain exhibited a ferroelectric phase, in which a photovoltaic effect was caused by the interaction between photogenerated charge carriers with the internal electric field formed by the spontaneous polarization of the ferroelectric phase.

The drying process, self-assembly of the proteins and the phase separation of a thermotropic liquid crystal (LC) from an initial aqueous solution represent a rich area of study. A focus of this work is to compare the behavior of two different proteins, bovine serum albumin [BSA] and lysozyme [Lys] in the ternary system through optical microscopy. During the drying process, the intensity profile shows three regimes in the presence of LC whereas no intensity variation is observed in its absence in both protein drops. The striking outcome is the presence of an umbilical defect of [+1] strength in every domain near the edge of BSA drop, whereas, each domain has a central dark region surrounded by a bright region in the dried Lys drop. Finally, the crack spacing in the dried Lys drop is reduced in the presence of LC whereas, no significant difference is found in the dried BSA drop.

Highly ordered wrinkling morphologies of liquid crystalline polymer films are demonstrated based on simple multi-rubbing. The spontaneous pattern formation of periodic wrinkling morphology is achieved through utilizing plasma treatment on a predefined alignment layer. The multi-directional ordering on the alignment layer obtained through selectively covering the alignment layer with a protective layer, which is chemically inert and keeps alignment properties during another rubbing process. The ordering of the wrinkle pattern can be tailored through a molecular orientation of liquid crystal (LC) and a process condition, including film thickness, plasma treatment, and rubbing. The proposed methods enable the spontaneous pattern formation of well-aligned one- or two-dimensionally periodic microstructures over a large area, without an additional template or patterning steps. Since the LC polymer incorporated the optical anisotropic mesogenic groups into polymer chains, it has an optical birefringence in the film and it can be utilized for optical devices requiring a microstructure on a surface.

The flow of heat in materials is generally perceived to be a slow process and, therefore, pump-probe techniques originally developed for ultrafast time-resolved optical spectroscopy are not an obvious source of technologies for advances in thermal-property measurements. Nevertheless, over the past 18 years, the work of approximately 30 dedicated students and postdoctoral researchers at the University of Illinois at Urbana-Champaign has developed time-domain thermoreflectance (TDTR) into a nearly universal, high-throughput tool for measuring the thermal conductivity of materials and the thermal conductance of materials interfaces. This article illustrates the utility of TDTR and surveys current topics in the science of heat conduction in materials with recent examples drawn from high-thermal-conductivity crystals of cubic boron phosphide and boron arsenide, structure–property relationships for thermal conductivity of amorphous polymers, and thermal conductivity switching in liquid-crystal networks.

We synthesized twin-mesogen epoxy polymer in which there were two 2,7-naphthalene benzoate as mesogens connected by four carbons alkyl chain and investigated the effects of higher-order structure changes due to the differences of alkyl chain length and mesogen groups on thermal conductivities. This polymer is abbreviated as TME2,7-NB4. NB means naphthalene benzoate and 4 means spacing carbon number. As a result, the thermal conductivity of TME2,7-NB4 was higher than that of TME2,7-NB8, but the coherent length D was less than that of TME2,7-NB8.

Defects arise when nematic liquid crystals are under topological constraints at the boundary. Recently the study of defects has drawn a lot of attention because of the growing theoretical and practical significance. In this paper, we investigate the relationship between two-dimensional defects and three-dimensional defects within nematic liquid crystals confined in a shell. A highly accurate spectral method is used to solve the Landau-de Gennes model to get the detailed static structures of defects. Interestingly, the solution is radial-invariant when the thickness of the shell is sufficiently small. As the shell thickness increases, the solution undergoes symmetry break to reconfigure the disclination lines. We study this three-dimensional reconfiguration of disclination lines in detail under different boundary conditions. In particular, we find that the temperature plays an important role in deciding whether the transition between two-dimensional defects and three-dimensional defects is continuous or discontinuous for the shell with planar anchoring condition on both inner and outer surfaces. We also discuss the characterization of defects in two- and three-dimensional spaces within the tensor model.

Stabilization of surface supported fluid lipid multilayers for underwater characterization is an essential step in making them useful for scalable cell culture applications such as high throughput screening. To this end, we used tetraethyl orthosilicate (TEOS), recently shown to stabilize fluid lipid films while maintaining their fluidity and functionality under water, to stabilize lipid multilayer micropatterns of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The treated multilayers were immersed under water and successfully imaged by atomic force microscopy (AFM), a difficult feat to perform on fluid lipid multilayers without TEOS treatment. The treated lipid multilayer showed an average swelling of approximately 18% in water but remained stable during the imaging process. The TEOS-treated lipid multilayers also proved compatible with cell culture as HeLa, MDCK, and HEK cell types all adhered and grew in high numbers over the multilayers. The results obtained here open the door to the use of fluid lipid multilayers in biotechnology applications such as microarray based high throughput cell assays.

Presbyopia is a ubiquitous age-related disability of the eye, affecting an estimated 1.04 billion people worldwide, reducing their ability to focus on nearby objects. The various solutions to this inevitable vision deterioration are not compromise-free, with a growing need for approaches beyond conventional spectacles. The research motivation for this work is the unique solution offered by liquid crystal (LC) contact lenses to create compromise-free vision across the whole field of view. The distinctive property of LC lenses is that they are switchable, with the application of a voltage activating the lens. The change in focal power is facilitated via a voltage-dependent change in refractive index of the LC. We have successfully demonstrated several versions of electrically switchable LC contact lenses with variable additional optical power of up to +3.00 D, ideal for the correction of presbyopia.

This paper offers a review of the optical and electro-optical performance recently demonstrated for the different modes of operation realized in nematic systems, including planar (homogeneous) and vertically aligned (homeotropic) aligned devices. The change in optical power obtained depends on the choice of geometry and LC material. A material with higher birefringence allows a thinner LC-lens layer to achieve a particular focal power. In the homeotropic geometry, the refractive index of the LC layer is a minimum in the ‘off’ state (ordinary refractive index, no) and the mode is polarization-independent, offering a significant advantage over planar lens designs. The construction is also simplified as only one alignment layer needs to be rubbed. Depending on the geometry used, continuously variable changes in focal power of up to +3.00D have been achieved. The response time of the lenses can be better than half a second, achieved with small applied voltages of ~7Vrms.

A further important stage in the optimization of the contact lenses is the inclusion of graphene as the electrodes. Conventional ITO electrodes are too brittle for these flexible optical systems. The paper also reviews the successful incorporation of graphene into the lenses, with excellent optical and electro-optical results. The device demonstrates the huge potential of graphene in an unconventional liquid crystal device geometry that includes curvature over a relatively large area.

We demonstrate a stabilized liquid crystal photoalignment using a surface-localized polymer method. A protection layer is developed on a photoalignment layer (PAL) through phase separation of a mixture composed of reactive monomers (RMs) and liquid crystals (LCs). The RM is polymerized on the PAL which enhances its stability against heat and light with short wavelength. The effects of the concentration and molecular structure of RMs on the electro-optical response and surface anchoring of photoaligned LC device are studied. The concentration of RMs affects the effective cell gap of the LC device. The rigid core length of the RM structure modulates the surface anchoring strength of the alignment layer. Both effective cell gap and surface anchoring strength are key elements for the enhanced dynamic response of LC devices.

A fully two-dimensional theoretical study of the electromagnetic wave propagation through Metal–Liquid Crystal–Metal (M–LC–M) waveguide structure is presented. Dispersion relations corresponding to both symmetric and antisymmetric-coupled surface plasmons polaritons modes in M–LC–M structure are derived and numerically solved. The effects of LC tilt angles on the effective refractive index and propagation length are proposed. The analytical method is in good agreement with those obtained from finite-difference time-domain simulation. The obtained analytic formula can be used as an efficient element in designing tunable ultrahigh nanoscale integrated plasmonic devices.

Responsive, biocompatible substrates are of interest for directing the maturation and function of cells in vitro during cell culture. This can potentially provide cells and tissues with desirable properties for regenerative therapies. Here, we demonstrate a straightforward and scalable approach to attach, align, and dynamically load cardiomyocytes on responsive liquid crystal elastomer (LCE) substrates. Monodomain LCEs exhibit reversible shape changes in response to cyclic heating, and when immersed in an aqueous medium on top of resistive heaters, shape changes are fast, reversible, and produce minimal temperature changes in the surroundings. We systematically characterized the strain response of LCEs in water and demonstrated the attachment and alignment of neonatal rat ventricular myocytes on LCE substrates. Cardiomyocytes attached to both static and stimulated LCE substrates, and under cyclic stimulation, cardiomyocytes aligned along the primary direction of strain. This work demonstrates the potential of LCEs as stimuli-responsive substrates for dynamic cell culture.

Small-angle light scattering (SALS) and wide-angle X-ray scattering (WAXS) were used to study the influence of heat treatment on the texture and microstructure of extruded films of high-performance thermotropic liquid crystal polymers (LCPs). The microstructure was correlated with tensile mechanical properties. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were supplied by the former Hoechst Celanese Corp. as 50 μm thick extruded films. The LCPs, denoted B-N, COTBP and RD1000, have B and N as common co-monomers and vary the other co-monomers. Thus, this study also enabled the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid-to-nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B-N and RD1000), or Ts→n increased significantly (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young’s modulus, E, along the extrusion axis increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as-extruded film. The results also showed that the optimum treatment time for improving the Young modulus was between 3 and 4 h. Wide-angle X-ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus.

In this paper we present fast response processes in dye doped liquid crystal cell with ZnSe layers on electrodes. Two-wave mixing and grating monitoring experiments were performed to characterize this liquid crystal system. With the help of photoconductive layers, the response time was reduced to a few milliseconds, which improved further the response rate in liquid crystal photorefractive system. A peak in response time versus applied voltage and unexpected oscillations in diffraction efficiency dynamics were observed, which implies unconventionally complex charge dynamics associated with SPPs excited at one of the photoconductive layer/liquid crystal interfaces.