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Dynamic control of motion at the molecular level is a core issue in promoting the bottom-up programmable modulation of sophisticated self-organized superstructures. Self-assembled artificial nanoarchitectures through subtle noncovalent interactions are indispensable for diverse applications. Here, the active solar renewable energy is used to harness cholesteric liquid crystal (CLC) superstructure devices via delicate control of the dynamic equilibrium between the concentrations of molecular motor molecules with opposite handedness. Thus, the spectral position and handedness of a photonic superstructure can be tuned continuously, bidirectionally, and reversibly within the entire working spectrum (from near-ultraviolet to the thermal infrared region, over 2 μm). With these unique horizons, three advanced photoresponsive chiroptical devices, namely, a mirrorless laser, an optical vortex generator, and an encrypted contactless photorewritable board, are successfully demonstrated. The sunlight-fueled chirality inversion prompts facile switching of functionalities, such as free-space optical communication, stereoscopic display technology, and spin-to-orbital angular momentum conversion. Motor-based chiroptic devices with dynamic and versatility controllability, fast response, ecofriendly characteristics, stability, and high efficiency have potential to replace the traditional elements with static functions. The inexhaustible natural power provides a promising means for outdoor-use optics and nanophotonics.

This study investigates the all-optical directional control of emission in a cholesteric liquid crystal (CLC)-infiltrated photonic crystal fiber (PCF) laser. A laser dye-doped CLC (LD-CLC) and an azobenzene LC-doped CLC (ALC-CLC), which are selectively infiltrated into the hollow core and holey-matrix cladding of the PCF, function as an optically active cavity and an all-optical emission direction-controllable light valve, respectively, in the photonic LC fiber (PLCF) laser. Experimental results show that the PLCF has a low energy threshold (approximately 63 nJ/pulse) and a large circular polarization anisotropy (g ≅ 2) in lasing output. The lasing output from the LD-CLC-filled core of the PLCF can be all-optical controlled to emit omni- or semi-directionally or to off-emit by controlling the isothermal phase transition of the CLC between the scattering focal conic state and the transparent isotropic state by the all-optical-induced reversible photoisomerization of the doped ALCs in the cladding region. The emission direction-controllable PLCF laser has significant potential in various applications, such as bio-image, photo-therapy, wearable devices, displays, sensors, and lighting.

This study employed wearable inertial sensors integrated with an activity-recognition algorithm to recognize six types of daily activities performed by humans, namely walking, ascending stairs, descending stairs, sitting, standing, and lying. The sensor system consisted of a microcontroller, a three-axis accelerometer, and a three-axis gyro; the algorithm involved collecting and normalizing the activity signals. To simplify the calculation process and to maximize the recognition accuracy, the data were preprocessed through linear discriminant analysis; this reduced their dimensionality and captured their features, thereby reducing the feature space of the accelerometer and gyro signals; they were then verified through the use of six classification algorithms. The new contribution is that after feature extraction, data classification results indicated that an artificial neural network was the most stable and effective of the six algorithms. In the experiment, 20 participants equipped the wearable sensors on their waists to record the aforementioned six types of daily activities and to verify the effectiveness of the sensors. According to the cross-validation results, the combination of linear discriminant analysis and an artificial neural network was the most stable classification algorithm for data generalization; its activity-recognition accuracy was 87.37% on the training data and 80.96% on the test data.

This work presents the design, fabrication, and characterization of a novel two-dimensional (2D) all-optical and polarization-independent tunable guided-mode resonance filter. This filter is composed of a 2D sub-wavelength photonic crystal nanostructure with a dye-doped liquid crystal layer in a doped-nanoparticle-induced homeotropic alignment. Experimental results show that the resonant wavelength of the filer can be all-optically and polarization-independently tuned for red- and blue-shifting if the cell is illuminated successively by UV and green beams. The all-optical and polarization-independent tunability of the filter is attributed to the phase transition between homeotropic ( H ) and isotropic ( I ) state, resulting in variations in the LC refractive index between the ordinary index ( n o) and refractive index in I state ( n i) via either UV-beam-induced trans-cis or green-beam-induced cis-trans back isomerization. In addition, the optically tunable cycle of the filter is repeatable for many times without significant decay or damage. This filter has potential applications, such as optical filters in signal processing, optical switches in communications technology, and optical sensors.

This study investigates and develops for the first time an electrically tunable liquid-crystal–polymer composite laser with a symmetric sandwich structure. This structure includes two identical pol...

Chameleons, which are among the poikilotherms, can rapidly change color for camouflage, communication and thermoregulation. These cold-blooded animals physiologically shift color through the active tuning of lattices of guanine nanocrystals within a superficial thick layer of dermal iridophores. This active tuning can be described as alternating different refractive indices of nano-reflectors, thereby generating interference of light waves. The self-regulation of the skin behind its dynamic color changing ability makes it the ultimate “biomimetic surface” and a continued source of inspiration. We presented a deformation-color multi-responsive actuator whose response is controlled by delicate light to mimic these adaptive functions. This soft smart material is developed by well-aligned cholesteric liquid crystal elastomers (CLCE). It performs a 185 nm wavelength shift of selective reflection and is switched by reacting to exposure time. Effective optical management is critical for the operation of many modern technologies. These results demonstrate distinctive potential opportunities for LC elastomers to control light, thereby enabling new applications of modern technologies to textiles, optics, and architecture.

Carocin S2 is a bacteriocin with a low molecular weight generated by

Nano- and microscale morphology endows surfaces that play conspicuous roles in natural or artificial objects with unique functions. Surfaces with dynamic regulating features capable of switching the structures, patterns, and even dimensions of their surface profiles can control friction and wettability, thus having potential applications in antibacterial, haptics, and fluid dynamics. Here, a freestanding film with light-switchable surface based on cholesteric liquid crystal networks is presented to translate 2D flat plane into a 3D nanometer-scale topography. The wettability of the interface can be controlled by hiding or revealing the geometrical features of the surfaces with light. This reversible dynamic actuation is obtained through the order parameter change of the periodic cholesteric organization under a photoalignment procedure and lithography-free mode. Complex tailored structures can be used to encrypt tactile information and improve wettability by pre-designing the orientation distribution of liquid crystal director. This rapid switching nano-precision smart surface provides a novel platform for artificial skin, optics, and functional coatings. This article is protected by copyright. All rights reserved.

Conventional polymer dispersed liquid crystal (PDLC) films have been successful as electrically-switchable screens for privacy applications. However, spatial patterning of the films so as to generate a visually appealing design, logo, or image typically requires intricate fabrication processes such as the use of prefabricated photomasks that do not allow for ondemand designs. Here, we report on the fabrication and characterisation of spatially patterned PDLC ‘pixels’ using drop-on-demand inkjet printing and demonstrate how these materials can be used to form a new generation of smart windows that consist of embedded images or company logos, which can be made to disappear with the application of a voltage. Following refinements to the material rheology and the subsequent successful deposition of individual PDLC droplets, arrays of PDLC pixels were printed at a resolution of 250 pixels per inch with an individual pixel size of 130 µm operating at an electric field strength (E) of E = 1.4 Vμm−1 . Finally, using the approach developed herein, these printed PDLC pixels have been arranged to form a college emblem that is embedded within a smart window that can be made to disappear with the application of a voltage.

A polarization controllable band-edge liquid crystal (LC) laser configuration is presented that provides on-demand control of the polarization state of the laser using a four electrode in-plane configuration to drive a nematic LC layer. By controlling the orientation of the electric field, and thus the orientation of the optic axis of the nematic LC, as well as the retardance, any laser polarization state (e.g., circular, elliptical etc) can, in principle, be created that is aligned along any desired direction in a plane perpendicular to the propagation direction. After calibrating the tuneable nematic device with a Helium-Neon laser that has a well-defined polarization state, control of the LC laser polarization is then demonstrated, where it is shown that different polarization states and orientations thereof can be obtained by changing the relative combination and amplitudes of the voltages applied to each of the four electrodes. It is found, however, that achieving a pure linear polarization state is challenging, which may indicate that the polarization from the LC laser is not a well-defined circularly polarized state. These thin-film LC lasers with full polarization control are potentially important for a variety of different applications ranging from the biomedical to the display industries.

Self-organized periodic micro/nanostructures caused by stimulus-responsive structural deformation often occur in anisotropic self-assembled supramolecular systems (e.g., liquid crystal systems). However, the long-range orderliness of these structures is often beyond control. In this article, we first demonstrate that a large-area disordered two-dimensional (2D) microgrid chiral structure appears in the cholesteric liquid crystal (CLC) reactive mixture because of the photopolymerization-induced Helfrich deformation effect under exposure to the single UV-laser beam. The result is attributed to the impact of an internal longitudinal strain, which is caused by the pitch contraction of the CLC-monomer region through the continuing compression of the thickening CLC polymer layer adhered on the illuminated substrate of the sample during photopolymerization. The experimental results further show that a one-dimensional (1D) UV-laser interference field can be used to effectively control the postformed 2D microgrid structure to arrange in an orderly manner throughout the large exposed area (an order of centimeter). The optimum ability for controlling the orderliness of the microgrid structure can be achieved if the spacing width of the interference field approximates the periodicity of the postformed 2D microgrids. Several factors, such as the pitch of the CLC mixture and the included angle and intensity of the two interfering laser beams, which influence the orderliness and properties of the 2D microgrid structure, are explored in this study. The result of this research opens a new page to improve the applicability of the Helfrich deformation phenomenon and further provides a reference platform for manipulating, modifying, and even tailoring periodic micro/nanostructures in self-organized supramolecular soft-matter systems for application in advanced optics/photonics.

This paper investigates the photoinduced change of refractive index in dye (methyl red, MR)-doped blue phase (DDBP) cells by illumination of a pump beam. Through excitation of light irradiation with proper photon energy, MR can transform from trans-state to cis-state and successively diffuse and anisotropically adsorb on the inner glass substrate of the DDBP cell along the direction perpendicular to the polarisation of the pump beam. The adsorbed MR molecules can effectively rotate the orientation of the liquid crystal (LC) molecules and thereby modulate the effective refractive index of the DDBP cell. The SEM images of the adsorbed regions of the illuminated DDBP samples were also taken for discussing the relation between the pump intensity and the photoinduced birefringence.

This study demonstrates a broadband-tunable photonic bandgap (PBG) and thermally convertible laser with an ultra-low lasing threshold based on a gradient-pitched cholesteric liquid crystal (CLC) polymer template. The lowest energy threshold of the laser is 16 nJ per pulse under a pumped diameter of ca. 250 μm (i.e., 0.33 μJ per pulse per mm2), a value that is superior to those of other band-edge lasers based on most dye/quantum-dot-doped CLC systems. Owing to its multiple advantages, such as high stability, ultra-low lasing threshold, wide-band and linear spatial PBG-tunability, and lasing-mode convertibility, the CLC template device can be potentially used for photonics and display applications.

In this paper, we propose a modified gravity method by introducing centrifugal force to promote the stacking of silica particles and the order of formed colloidal crystals. In this method, a monodispersed silica colloidal solution is filled into empty cells and placed onto rotation arms that are designed to apply an external centrifugal force to the filled silica solution. When sample fabrication is in progress, silica particles are forced toward the edges of the cells. The number of defects in the colloidal crystal decreases and the structural order increases during this process. The highest reflectivity and structural order of a sample was obtained when the external centrifugal force was 18 G. Compared to the samples prepared using the conventional stacking method, samples fabricated with centrifugal force possess higher reflectivity and structural order. The reflectivity increases from 68% to 90%, with an increase in centrifugal force from 0 to 18 G.

Influenza, pneumonia, and pathogenic infection of the respiratory system are boosted in cold environments. Low temperatures also result in vasoconstriction, restraint of blood flow, and decreased oxygen to the heart, and the risk of a heart attack would increase accordingly. The present face mask fabric fails to preserve its air-filtering function as its electrostatic function vanishes once exposed to water. Therefore, its filtering efficacy would be decreased meaningfully, making it nearly impracticable to reuse the disposable face masks. The urgent requirement for photothermal fabrics is also rising. Nanobased polyethyleneimine-polypyrrole nanopigments (NPP NPs) have been developed and have strong near-infrared spectrum absorption and exceptional photothermal convertible performance. Herein, the mask fabric used PE-fiber-constructed membrane (PEFM) was coated by the binding affinity of the cationic polyethyleneimine component of NPP NPs forming NPP NPs-PEFM. To the best of our knowledge, no study has investigated NPP NP-coated mask fabric to perform infrared red (solar or body) photothermal conversion efficacy to provide biocompatible warming, remotely photothermally captured antipathogen, and antivasoconstriction in vivo. This pioneering study showed that the developed NPP NPs-PEFM could be washable, reusable, breathable, biocompatible, and photothermal conversable for active eradication of pathogenic bacteria. Further, it possesses warming preservation and antivasoconstriction.

This paper presents a focusing efficiency and focal length tunable planar Fresnel lens in reflection type based on azo-dye-doped cholesterol liquid crystal film. The Fresnel-like pattern of a pumping beam can be formed by a Sagnac interferometer. When the azo-dye molecules are irradiated by the pumping beam, the photoalignment effect will be induced in the bright (odd) zones due to the trans&ndash, cis photoisomerization of azo-dye molecules. Thus, the structures of cholesteric liquid crystals in the odd zones will reorient from the imperfectly planar textures to the perfectly planar textures. The different structures of cholesteric liquid crystals in two adjacent zones will give rise to phase difference for the reflected light and thus function as a Fresnel lens. The focusing efficiency of the proposed Fresnel lens can be controlled by the applied voltages and affected by the polarization state of incident light. Moreover, various focal lengths of the Fresnel lens can be achieved by rewriting a different center radius of the Fresnel-like pattern.

In this paper, we demonstrate a flexoelectro-optic liquid crystal phase-only device that uses a chiral nematic reflector to achieve full 2π phase modulation. This configuration is found to be very tolerant to imperfections in the chiral nematic reflector provided that the flexoelectro-optic LC layer fulfils the half-wave condition. Encouragingly, the modulation in the phase, which operates at kHz frame rates, is also accompanied by low amplitude modulation. The configuration demonstrated herein is particularly promising for the development of next-generation liquid crystal on silicon spatial light modulators.

The challenges associated with developing a flexible defect-mode liquid crystal (LC) laser are addressed in this paper. To begin with, we discuss the process for creating a well-aligned photopolymerized film of chiral nematic LC using various surface alignment layers such as polyvinyl alcohol, sulphonic azo-dye and rubbed polyimide. A single mode flexible defect-mode laser is demonstrated with an excitation threshold fluence of 60μJ/cm2/pulse. In accordance with previous studies, results from simulations based on the 4×4 Berreman model show that the wavelength and the number of laser modes are determined by the thickness of the defect layer. The proposed flexible laser can be used to form lasers that can be integrated into conformable platforms and that can be used to control the beam direction without the need for additional optical components.

We have demonstrated a Liquid crystal (LC) analog phase modulator based on the flexoelectric-optic effect that can achieve full 2π phase modulation with sub-millisecond switching speed. The LC mixture in the device consists of the bimesogen CBC7CB with chiral dopant R5011 that can exhibit ±𝜋/4 rotation of the optic axis for an electric field of ±4.2Vμm^(-1). This is then converted to a ±π phase modulation with the aid of a chiral reflector and a quarter waveplate. The residual amplitude modulation is found to be very low, and we show how these elements can be combined to form a integrated device.

This study investigated the effects of whole body vibration (WBV) training combined with blood flow restriction (BFR) on muscle fitness. Twenty physically inactive adults were randomly assigned to ...

Laser emission from a flexible defect‐mode structure consisting of two photopolymerized liquid crystal thin films separated by a dye‐doped polymethylmethacrylate defect layer is demonstrated. A simple and cost‐effective film transfer technique is used to fabricate the flexible laser and the corresponding laser emission characteristics, which shows single‐mode laser emission at λ = 582 nm, with an excitation threshold of Eth = 12.3 ± 0.5 µJ cm−2 per pulse and a slope efficiency of ηs = 6.0 ± 0.3%, are presented. The polarization state of the laser emission are also presented and are compared with the findings reported in the literature. Finally, laser‐beam steering is demonstrated up to 42° by subjecting the device to a mechanically induced deformation that creates a radius of curvature of 5 mm, which is of potential interest for conformable and wearable technology platforms.

We developed a new format for liquid crystal (LC)-based multi-microfluidic immunoassays, hosted on a polydimethylsiloxane substrate. In this design, the orientations of the LCs were strongly affected by the interface between the four microchannel walls and surrounding LCs. When the alignment layer was coated inside a microchannel, the LCs oriented homeotropically and appeared dark under crossed polarizers. After antigens bound to the immobilized antibodies on the alignment layer were coated onto the channel walls, the light intensity of the LC molecules changed from dark to bright because of disruption of the LCs. By employing pressure-driven flow, binding of the antigen/antibody could be detected by optical signals in a sequential order. The multi-microfluidic LC biosensor was tested by detecting bovine serum albumin (BSA) and an immunocomplex of BSA antigen/antibody pairs, a protein standard commonly used in labs. We show that this multi-microfluidic immunoassay was able to detect BSA and antigen/antibody BSA pairs with a naked-eye detection limitation of &minus, 0.01 &micro, g/mL. Based on this new immunoassay design, a simple and robust device for LC-based label-free microfluidic immunodetection was demonstrated.

Refilling cholesteric liquid crystal (CLC) template gratings with circular polarization, wavelength selectivity, and dual operation mode are first demonstrated. The gratings with template and nontemplate regions are obtained through the two-beam interfering photo-polymerization, washing-out, and refilling procedure. The refilling CLC has different chiral handedness (left or right) and reflection band (at green and red regions). When the wavelength of a probe beam is within the refilled CLC reflection band of the nontemplate region, the device works as an amplitude grating since the sample in the template and nontemplate regions reflects distinct colour region. In addition, the diffraction intensity of the grating can be electrically controlled. Therefore, this CLC-based device can be potentially used in controllable diffraction elements in optics.

This work fabricates a fishnet grating by exerting two one-dimensional (1D) holographic interference fields with mutually orthogonal grating vectors separately on the substrates of a dye-doped liquid crystal (DDLC) cell. The DDLC mixture in the cell includes a nematic LC, methyl red (MR) dye, and 4-methoxyazobenzene (4MAB) dye. The fishnet grating is formed because the periodical adsorption of the MR dye on the irradiated surfaces of the cell causes the anisotropic photoalignment of the LC. The fishnet grating can be erased (recovered) by the illumination of a UV (green) beam since the trans → cis (cis → trans) isomerization of the 4MAB dye causes the isothermal nematic → isotropic (isotropic → nematic) phase transition of the LC. Such a grating can be used to develop optically controllable photonic crystals. Simulated results depict that a photoresist-coated plastic substrate that is exposed to the fishnet pattern of a 2D grating can be used to develop terahertz fishnet metamaterials, and their resonance spectra can be passively tuned by moving the substrate and lens that forms the fishnet pattern during fabrication. Therefore, the mask-free photolithography can be used to fabricate passively tunable terahertz filters.

Dye-doped nematic liquid crystal refilled gradient-pitched enantiomorphic cholesteric liquid crystal polymer templates are demonstrated. The enantiomorphic device has high reflectivity and wide spectral tunability throughout the entire visible region. This device can also provide low threshold lasing emission with both right- and left-circular polarizations from the blue to the red region.

Currently, the remaining grand challenge liquid crystal displays (LCD's) face in the market is response time (a few milliseconds), which is ∼ 100 times slower than that of OLEDs (∼ 0.1 ms). To achieve the goal of sub-millisecond response time and suppressing the colour breakup issue, blue phase liquid crystal (BPLC) is emerging as a strong candidate. The blue phase is stable in a narrow temperature range and consists of individual liquid crystal molecules arranged into double twisted cylinders. However, the strong wavelength dependent scattering of circularly polarised light dependent on lattice constant and crystal orientation leads to striking visual colour effects which hint at future display applications. To improve temperature stability, cross-linked polymer networks have been used to stabilize the BPLC lattice structure and extend the blue phase temperature range to more than 95°C including room temperature. However, this approach leads to randomly oriented blue phase (BP) structures with poor optical transmittance, contrast and high operating voltage (>100 V) [1].

Liquid crystals (LCs) are distinctive materials that are applicable to a wide range of disciplines, such as continuum mechanics, optics of anisotropic media, statistical physics, and crystallography. The diverse structures and eye-catching topological defects of LCs in confined geometries are affected by nematic elasticity, chirality, and surface anchoring. Herein, we report the formation and detailed configuration of cholesteric LC (CLC) microdroplets with different pitches pierced by electrospun poly(methyl methacrylate) microfibers. Two kinds of surface anchoring, namely, homeotropic anchoring at the air–CLC droplet interface and planar anchoring at the fiber–CLC droplet interface, coexist in this system. By controlling temperature and light irradiation, the system exhibits thermal- and photo-dependent LC morphological and topological evolutions. The observed structures are complemented by numerical simulations of possible director fields decorated by defects. The externally controllable CLC necklaces constitute extraordinary systems for exploring the morphology and topological defects and open a route for applications in topological remote control, nanoscience, biomedical research, and the development of devices based on topologically structured soft media.

In this study, the all-optical control properties of photonic crystals based on self-assembled chiral-azobenzene-doped blue phase liquid crystals (CA-BPLCs) were investigated. The difference in the photothermal characteristics of CA-BPLCs with and without homogeneous surface alignment was discussed. Results revealed that surface alignment could induce more uniform and diverse blue phase (BP) structures, including BPII, BPI, and BPS-like phases during cooling. Consequently, the temperature range of BP was wider than that of the sample without surface alignment. All-optical control experiments with light illumination were then performed on the aligned or nonaligned CA-BPLC samples. During continuous irradiation with light beams at wavelengths of 405 and 450 nm, CA dopants underwent trans&rarr, cis and cis&rarr, trans back photoisomerizations, respectively. These processes promoted isothermal phase transition and wavelength shifting, which further enabled the all-optical control of the CA-BPLC samples. Various optical control modes of BPLC could be achieved through phase change and wavelength shifting by appropriately selecting the working temperature and surface treatment of BPLC. This study could be further used as a basis for developing photoswitchable and tunable BPLC photonic devices, such as light-controllable gratings, filters, mirrors, and lasers.

In this communication, the fabrication of electrically tunable bifocal liquid crystal (LC) microlenses using drop‐on‐demand inkjet printing is demonstrated. By treating the glass substrate with a homeotropic alignment layer, the printed droplets are found to form plano‐convex lenses with focal lengths in the range of 220–463 µm, depending upon the number of droplets deposited at each location on the substrate. The precision of the process allows for the microlenses to be deposited in between in‐plane indium tin oxide electrodes. In the presence of a high amplitude electric field, the director within the LC droplets is observed to align with the direction of the applied field, but without any accompanying distortion in the droplet profile. However, these changes in the LC director alignment are found to result in a bifocal behavior rather than a continuous change in the focal length. It is also found that there exists a range of voltages for which two focal planes are observed.

An infrared (IR) reflector that has ultra-wide reflection band and high reflectance was successfully fabricated based on an enantiomorphic chiral polymer composite template-made method involving UV-curing, washing-out, stacking, and refilling. In this study, an IR reflector reflecting >80% of incoming solar IR light from 800 nm to 1500 nm and retaining acceptable transmittance in the visible region is demonstrated. This undertaking is achieved by stacking two enantiomorphic double-polymerized chiral polymer templates with large longitudinal pitch gradients as a composite template cell designed for the near-IR region. Heat insulation test reveals that the temperature can be effectively lowered by 2 °C–3 °C by using the IR reflector, thereby indicating that a considerable amount of incident heat could be isolated and a significant amount of energy could be saved by cooling. The sample has potential in green and military applications, such as energy-saving green windows and anti-IR devices.