Nanoimprinting-lithography-induced self-aligned liquid crystals for novel multifunctional optical films

Chiu, Chih-Ho; Kuo, Hui-Lung; Chen, Pin-Cheng; Wen, Chun-Ming; Liu, Yichun; Chen, Huang‐Ming Philip

doi:10.1063/1.2173222

Cited by 44 publications

(10 citation statements)

References 23 publications

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“…Varghese et al described a micro-rubbing technique for LC alignment [109]. Nano-imprint lithography could be used for patterned alignments in microscale [110][111][112].…”

Section: Discussionmentioning

confidence: 99%

Nematic Liquid Crystal Composite Materials for DC and RF Switching

2019

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Liquid Crystals (LCs) are widely used in display devices, electro-optic modulators, and optical switches. A field-induced electrical conductivity modulation in pure liquid crystals is very low which makes it less preferable for direct current (DC) and radio-frequency (RF) switching applications. According to the literature, a conductivity enhancement is possible by nanoparticle doping. Considering this aspect, we reviewed published works focused on an electric field-induced conductivity modulation in carbon nanotube-doped liquid crystal composites (LC-CNT composites). A two to four order of magnitude switching in electrical conductivity is observed by several groups. Both in-plane and out-of-plane device configurations are used. In plane configurations are preferable for micro-device fabrication. In this review article, we discussed published works reporting the elastic and molecular interaction of a carbon nanotube (CNT) with LC molecules, temperature and CNT concentration effects on electrical conductivity, local heating, and phase transition behavior during switching. Reversibility and switching speed are the two most important performance parameters of a switching device. It was found that dual frequency nematic liquid crystals (DFNLC) show a faster switching with a good reversibility, but the switching ratio is only two order of magnitudes. A better way to ensure reversibility with a large switching magnitude is to use two pairs of in-plane electrodes in a cross configuration. For completeness and comparison purposes, we briefly reviewed other nanoparticle- (i.e., Au and Ag) doped LC composite’s conductivity behavior as well. Finally, based on the reported works reviewed in this article on field induced conductivity modulation, we proposed a novel idea of RF switching by LC composite materials. To support the idea, we simulated an LC composite-based RF device considering a simple analytical model. Our RF analysis suggests that a device made with an LC-CNT composite could show an acceptable performance. Several technological challenges needed to be addressed for a physical realization and are also discussed briefly.

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“…Varghese et al described a micro-rubbing technique for LC alignment [109]. Nano-imprint lithography could be used for patterned alignments in microscale [110][111][112].…”

Section: Discussionmentioning

confidence: 99%

Nematic Liquid Crystal Composite Materials for DC and RF Switching

2019

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“…A mixture (RMS03-013, Merck) containing an initiator, reactive liquid-crystalline monomer, and a volatile organic solvent is spin-coated on an alignment layer nanoimprinted on the IOL substrate. Upon drying, the reactive mesogens are then polymerized to be an aligned LCP layer by exposing the sample to radiation that initiates the polymerization process 59 (Fig. 4a ).…”

Section: Methodsmentioning

confidence: 99%

Geometric-phase intraocular lenses with multifocality

et al. 2022

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We demonstrate a new type of multifocal and extended depth of focus (EDOF) intraocular lenses (IOLs) embedding μm-thin geometric phase (GP) lens layers. As an emerging approach for lens phase design, the GP modulated IOLs outperform conventional diffractive IOLs in multifocality while completely avoiding the clinically undesirable demand for additional surface patterns to standard monofocal IOL designs. The number of foci and light splitting ratio of the GP IOLs are adjusted by changing the number of stacked GP layers and the thickness of each layer. Bifocal and trifocal GP IOLs are fabricated by radial alignment of anisotropic orientation in UV-curable liquid crystal polymers. After characterizing the defocus image and modulation transfer function of the GP IOLs, it is expected that GP IOLs will alleviate the most common problems associated with multifocal and EDOF IOLs, blurred vision and photic phenomena caused by light scattering and posterior capsule opacification.

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“…Email: Youngwoo.yi@colorado.edu patterns has been studied widely for thermotropic LCs [10][11][12]. Nanoimprinting can generate polymer films with topographic patterns in a simple and practical way and such films have been extensively used to demonstrate alignment of a variety of LCs in novel ways [13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Orientation of chromonic liquid crystals by topographic linear channels: multi-stable alignment and tactoid structure

Clark

2013

Liquid Crystals

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We study the alignment behaviour of the chromonic liquid crystal phases of sunset yellow (SSY)/water, disodium cromoglycate (DSCG)/water and their mixtures when confined in cells by polymer films topographically imprinted with linear channels of 250 nm width, depth and spacing. A variety of novel alignment effects are generated by contact with such a patterned surface, as follows. Nematic DSCG and nematic SSY at low concentration and their nematic mixtures orient with the long axes of stacked chromonic aggregates on average parallel to the channels, that is, with the molecular planes normal to the channel axis. These oriented nematics exhibit isotropic/nematic tactoids aligned with their major axes along the channels. Two geometries of the tactoids, elliptic cylinder and rectangular cuboid with hemi cylindrical ends are observed. Additionally, a transition of DSCG tactoids from a three-dimensional (3D) director configuration to a two-dimensional one is observed when the tactoids on one surface of a cell touch the other surface of the cell. In SSY solutions of sufficiently high concentration, multi-stable alignment is found, including preferential in-plane orientation of the director parallel to, perpendicular to and 45 • rotated from the channels.

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Nanoimprinting-lithography-induced self-aligned liquid crystals for novel multifunctional optical films

Cited by 44 publications

References 23 publications

Nematic Liquid Crystal Composite Materials for DC and RF Switching

Nematic Liquid Crystal Composite Materials for DC and RF Switching

Geometric-phase intraocular lenses with multifocality

Orientation of chromonic liquid crystals by topographic linear channels: multi-stable alignment and tactoid structure

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