Fast-switching optically isotropic liquid crystal nano-droplets with improved depolarization and Kerr effect by doping high k nanoparticles

Advanced Optical Materials

et al. 2022

Liquid crystal (LC) droplets have fascinating properties, such as anisotropic properties, in response to external stimuli. As LC droplet size may determine the proper application of soft composites, various results from numerical simulations and experimental observations of LC droplets are reported. Here, detailed topological responses of individual bipolar droplets to electric fields, are shown. The integration of each response influences the entire electro‐optic behavior. Monodispersed LC bipolar droplets are fabricated in a polyvinyl alcohol‐dissolved aqueous solution via a membrane‐emulsification method. The planar anchoring, provided by the polyvinyl alcohol surface, and surface elasticity, guide the entire LC director configuration, associated with topological defects, in the droplets. By simply blade‐coating the solution, bipolar axes of the droplets can be randomly placed on a flat substrate. Two different subsequential stages are found when applying voltages: 1) director reorientation, which is threshold‐less and 2) topological defect movement, which exhibits a threshold‐like behavior. Various initial directions of the bipolar axes with respect to the field direction provide the transition voltage between these two stages. It is believed that this study can provide important clues to handle several fundamental issues in electro‐optics of encapsulated LCs, such as the determination of response times, threshold, and operating voltages.

Section: Introductionmentioning

confidence: 99%

Field‐Induced Structural Transitions in Liquid Crystal Microemulsions

Kim

Advanced Optical Materials

et al. 2022

“…The great advantages of OILCs are resilience to external pressures, optically isotropy in the field‐off state, wide viewing angle, cell gap independence, alignment layer‐free, and rubbing‐free allows simplification of device fabrication . In addition, OILC exhibits fast switching times . Owing to these revolutionary benefits many potential users became fascinated by OILCs.…”

Section: Introductionmentioning

confidence: 99%

Fast Switchable Micro‐Lenticular Lens Arrays Using Highly Transparent Nano‐Polymer Dispersed Liquid Crystals

Bhattacharyya²,

et al. 2019

Adv Materials Inter

the lower driving voltages. However, the parallax barrier reduces transmittance to half, causes resolution loss and limits viewing angles due to slits in front of the display panel and the flat-type lenticular lens are not switchable. Furthermore, the switchable lenticular lens which utilizes nematic LC requires large cell gap to achieve enough periodic phase modulation between the adjacent electrodes for realizing the lensing effect, which results in slow switching response time in conventional devices with pure nematic LC. Besides, the quality of displayed image becomes distorted when the externally applied force is strong enough. Therefore, further investigations are required to achieve switchable LC lens with fast response time and a mechanical shock resilient network, which could satisfy the future demands of electronic devices with flexibility and bendability.Contrary to shortcomings of traditional modes, a binary composite of the optically isotropic liquid crystal (OILC) was introduced. Currently, there are two types of binary composites attracting liquid crystal display industrial research, one is nanostructured polymer dispersed liquid crystals (nano-PDLCs) and the other is the polymer-stabilized blue phase (PSBP). The great advantages of OILCs are resilience to external pressures, optically isotropy in the field-off state, wide viewing angle, cell gap independence, alignment layer-free, and rubbing-free allows simplification of device fabrication. [5][6][7][8] In addition, OILC exhibits fast switching times. [9][10][11][12] Owing to these revolutionary benefits many potential users became fascinated by OILCs.In addition, the nano-PDLC is a composite consisting of low molecular weight prepolymer and the LC. Optimized UV light intensity and materials, and concentration ratio of monomer to LC under ambient conditions result in the nanosized LC droplets encapsulated by polymer network viz., nano-PDLC in which the droplet size is smaller than the wavelength of visible light. [8,12] In addition, the random orientation of the LC director results in the optically isotropic phase so that the nano-PDLC exhibits excellent black state under the crossed polarizers. On the other hand, the PSBP also shows an optically isotropic phase with very fast electro-optic response. However, temperature sensitive phase separation and high hysteresis are hindering their extensive industrial applications. [7,13,14] Utilizing the benefits of OILCs, several photonic devices including polarization independent tunable microlens, [15][16][17] A polarization-dependent micro-lenticular lens array (MLA) based on phase modulation of the nanostructured polymer dispersed liquid crystal (nano-PDLC) is proposed. The transparent and optically isotropic composite is formed by photo-polymerization induced phase separation of the LC and pre-polymer mixture. The gradient field is generated by interdigitated electrodes and the LCs in nanosized droplets in nano-PDLC orient along the field direction, resulting in field-induced birefringence from the o...

“…The OILC phase achieved from nano-phase separated LC exhibits a high transparency and very fast response time which is essential requirement for developing the switchable lenticular lenses. Additionally, the OILC also retains a great advantage of easy processing and, remarkably resistance to external mechanical forces that is feasible for emerging technologies such as bendable and flexible devices [5][6][7]. Besides, for eliminating the feeble light scattering, smaller size LC droplets than the wavelength of visible light is highly desirable.…”

Section: Introductionmentioning

confidence: 99%

35‐3: Polarization Dependent Switchable Micro‐lenticular Lens Arrays using Optically Isotropic Liquid Crystals

Symp Digest of Tech Papers

et al. 2019

We propose polarization-dependent micro-lenticular lens arrays (MLAs) based on optical phase modulation by reorientation of nano-sized LC droplets of the optically isotropic liquid crystals (OILC). On applying gradient in-plane field, the gradient refractive index is generated between the electrodes, giving rise to the MLAs with the focal length of 22 µm at 50 V rms and switching time of few ms. The OILC can also be applied to switchable microlens. The proposed device has a potential to be applicable to 2D/3D switchable optical lens.