Superior electro-optics of nano-phase encapsulated liquid crystals utilizing functionalized carbon nanotubes

Manda, Ramesh; Bhattacharyya, S. P.; Cho, Kyeong Jun; Kim, Tae Hyung; Lim, Young Jin; Lee, Seung Hee

doi:10.1016/j.compositesb.2019.01.091

Cited by 30 publications

(12 citation statements)

References 27 publications

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“…A response time of around 4 ms was obtained with the addition of a small amount of dye to a polymer-dispersed liquid crystal (PDLC) or functionalized carbon nanotubes dispersed in optically isotropic LCs. However, in this case, the excellent response speed is valid only for operation at a relatively high voltage 17 , 18 . Blue-phase LCs have a response time of 0.5 ms, but they still have drawbacks, such as hysteresis, high operation voltage, and narrow temperature range 19 .…”

Section: Introductionmentioning

confidence: 99%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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The dispersion of organic N-benzyl-2-methyl-4-nitroaniline (BNA) in nematic liquid crystals (LCs) is studied. BNA doping decreases the threshold voltage of cell because of the reduced splay elastic constant and increased dielectric anisotropy of the LC mixture. When operated in the high voltage difference condition, the BNA-doped LC cell has a fall time that is five times faster than that of the pure one because of the decrements in the threshold voltage of the cell and rotational viscosity of the LC mixture. The additional restoring force induced by the BNA's spontaneous polarization electric field (SPEF) also assists to decrease the fall time of the LC cell. The decreased viscosity can be deduced from the decrements in phase transition temperature and associated order parameter of the LC mixture. Density functional theory calculation demonstrates that the BNA dopant strengthens the absorbance for blue light, enhances the molecular interaction energy and dipole moment, decreases the molecular energy gap, and thus increases the permittivity of the LC mixture. The calculation also shows that the increased dipole moment, polarizability, and polarizability anisotropy increase the dielectric anisotropy of the LC mixture, which agrees with the experimental results well. BNA doping has a promising application to the fields of LC devices and displays. Nematic liquid crystals (LCs) are extraordinarily responsive and optically uniaxial materials. Nematic LCs have been extensively used in diverse applications, such as optical nonlinearity, optical phase modulators, microdisplays, flat panel displays, optical antennas, and optical switching, due to their electro-optical property and other admirable features 1-5. LCs with a fast response are vital in removing motion blur in moving pictures and resolving cross-talk in 3D displays 6-9. The response time of LCs should be less than 3 ms to diminish motion blur and cross-talk. Several techniques have been proposed to resolve this issue, and they include tuning the viscosity of materials 10 , varying the anchoring energy 11 , changing the electrode shape and driving scheme 12 , changing the cell gap 13 , modifying the guest-host material 14 , and applying new switching modes 15. The improvements in the electro-optical properties of LCs with the dispersion of different gust entities were presented recently. For example, Y. Dai et al. demonstrated that the incorporation of γ-Fe 2 O 3 nanoparticles into LCs results in a response time of 4.75 ms with the application of the overdriving scheme, which is three times faster than pure LCs 16. A response time of around 4 ms was obtained with the addition of a small amount of dye to a polymer-dispersed liquid crystal (PDLC) or functionalized carbon nanotubes dispersed in optically isotropic LCs. However, in this case, the excellent response speed is valid only for operation at a relatively high voltage 17,18. Blue-phase LCs have a response time of 0.5 ms, but they still have drawbacks, such as hysteresis, high operation voltage, and narrow t...

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Section: Introductionmentioning

confidence: 99%

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Selvaraj

Karthick

Brahadeeswaran

et al. 2020

Sci Rep

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“…The threshold voltage (Vth) of the PEDOT: PSS doped OILC change with the concentration of dopant in the composite medium. So, the modified Vth of the PEDOT: PSS doped OILC is written as [11,14], 1 ,…”

Section: Sid 2020 Digest • 1941 Issn 0097-996x/20/4803-1941-$100 © 2mentioning

confidence: 99%

“…Even after these efforts, the high driving voltage is still an unsolved issue for practical applications. In previous report, the field screening effect in the polymer matrix was minimized up to some extent of the dopant concentration but a higher concentration of dopant causes agglomerations in the polymer matrix [11]. Considering these efforts, we also challenge to improve the conductivity of polymer matrix so that the applied field strength should pass without shielding by the polymer matrix.…”

Section: Introductionmentioning

confidence: 99%

“…To overcome the drawback of OILCs, a few different approaches were reported in the literature to reduce the driving voltage of the OILCs. Among them, one is the utilization of flexible/weak anchored monomers with relative diluents [9], using a LC with high birefringence and dielectric anisotropy to get the high K (1 nm/V 2 ) [10], doping functionalized-carbon nanotubes (f-CNTs) [11], and using the acrylate monomers [12]. Even after these efforts, the high driving voltage is still an unsolved issue for practical applications.…”

Section: Introductionmentioning

confidence: 99%

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P‐149: Enhanced Electro‐Optic Performances of the Optically Isotropic Liquid Crystal Displays Utilizing PEDOT: PSS

Manda

Lee

et al. 2020

Symp Digest of Tech Papers

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Optically isotropic liquid crystal (OILC) composite film in which nano-sized LC droplets are embedded in a polymer matrix is highly useful for bendable displays and wearable photonics but a high operating voltage due to field shielding effect of the insulting matrix and low Kerr constant needs to be overcome. To address this challenge, a small amount of conductive materials PEDOT: PSS is doped into the OILCs. The LC cells with 2 and 3.5 wt% PEDOT: PSS doped OILCs exhibit improved driving voltages by 6.5% and 11.7% and on-state transmittance by 10.3% and 30.1%, respectively, compared to conventional one. In addition, faster switching response times are achieved while the dark level remains to be unaltered.

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“…Most recently, the feeble light scattering was eliminated by utilizing the twisted LC behavior inside the droplet [8] and various pre-polymers [9]. In addition, we also achieved reduced driving voltages by incorporating conductive materials into the OILC system [10]. Considering these advantages, few photonic devices includes polarization independent tunable microlens [11][12][13] and diffraction gratings [14,15] were developed.…”

Section: Introductionmentioning

confidence: 99%

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

Manda

Lee

et al. 2019

Symp Digest of Tech Papers

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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.

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Superior electro-optics of nano-phase encapsulated liquid crystals utilizing functionalized carbon nanotubes

Cited by 30 publications

References 27 publications

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

Electro-optical effects of organic N-benzyl-2-methyl-4-nitroaniline dispersion in nematic liquid crystals

P‐149: Enhanced Electro‐Optic Performances of the Optically Isotropic Liquid Crystal Displays Utilizing PEDOT: PSS

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

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