scholarly journals Signal Amplification in an Optical and Dielectric Biosensor Employing Liquid Crystal-Photopolymer Composite as the Sensing Medium

Biosensors ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 81
Author(s):  
Hassanein Shaban ◽  
Shih-Chun Yen ◽  
Mon-Juan Lee ◽  
Wei Lee
Keyword(s):  
Dielectric Constant ◽  
Liquid Crystal ◽  
Uv Irradiation ◽  
Signal Amplification ◽  
Limit Of Detection ◽  
Optical Signal ◽  
Uv Exposure ◽  
Dielectric Anisotropy ◽  
Optical Texture ◽  
Potential Development

An optical and dielectric biosensor based on a liquid crystal (LC)–photopolymer composite was established in this study for the detection and quantitation of bovine serum albumin (BSA). When the nematic LC E7 was doped with 4-wt.% NOA65, a photo-curable prepolymer, and photopolymerized by UV irradiation at 20 mW/cm2 for 300 s, the limit of detection determined by image analysis of the LC optical texture and dielectric spectroscopic measurements was 3400 and 88 pg/mL for BSA, respectively, which were lower than those detected with E7 alone (10 μg/mL BSA). The photopolymerized NOA65, but not the prepolymer prior to UV exposure, contributed to the enhanced optical signal, and UV irradiation of pristine E7 in the absence of NOA65 had no effect on the optical texture. The effective tilt angle θ, calculated from the real-part dielectric constant ε’, decreased with increasing BSA concentration, providing strong evidence for the correlation of photopolymerized NOA65 to the intensified disruption in the vertically oriented LC molecules to enhance the optical and dielectric signals of BSA. The optical and dielectric anisotropy of LCs and the photo-curable dopant facilitate novel quantitative and signal amplification approaches to potential development of LC-based biosensors.

scholarly journals Azimuthal Anchoring Strength in Photopatterned Alignment of a Nematic

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 675
Author(s):  
H. Nilanthi Padmini ◽  
Mojtaba Rajabi ◽  
Sergij V. Shiyanovskii ◽  
Oleg D. Lavrentovich
Keyword(s):  
Liquid Crystal ◽  
Point Defects ◽  
Elastic Energy ◽  
Separation Distance ◽  
Thin Layers ◽  
Uv Exposure ◽  
Surface Anchoring ◽  
Anchoring Strength ◽  
Spatially Varying

Spatially-varying director fields have become an important part of research and development in liquid crystals. Characterization of the anchoring strength associated with a spatially-varying director is difficult, since the methods developed for a uniform alignment are seldom applicable. Here we characterize the strength of azimuthal surface anchoring produced by the photoalignment technique based on plasmonic metamsaks. The measurements used photopatterned arrays of topological point defects of strength +1 and −1 in thin layers of a nematic liquid crystal. The integer-strength defects split into pairs of half-integer defects with lower elastic energy. The separation distance between the split pair is limited by the azimuthal surface anchoring, which allows one to determine the strength of the latter. The strength of the azimuthal anchoring is proportional to the UV exposure time during the photoalignment of the azobenzene layer.

scholarly journals Alignment Layer of Liquid Crystal Using Plant-Based Isoeugenol-Substituted Polystyrene

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 547
Author(s):  
DaEun Yang ◽  
Kyutae Seo ◽  
Hyo Kang
Keyword(s):  
Liquid Crystal ◽  
Surface Energy ◽  
Polymer Film ◽  
Uv Irradiation ◽  
Molar Content ◽  
Polymer Modification ◽  
Alignment Layer ◽  
Energy Value ◽  
Alignment System ◽  
Molar Percent

We synthesized a series of renewable and plant-based isoeugenol-substituted polystyrenes (PIEU#, # = 100, 80, 60, 40, and 20, where # is the molar percent content of isoeugenol moiety), using polymer modification reactions to study their liquid crystal (LC) alignment behavior. In general, the LC cells fabricated using polymer film with a higher molar content of isoeugenol side groups showed vertical LC alignment behavior. This alignment behavior was well related to the surface energy value of the polymer layer. For example, vertical alignments were observed when the polar surface energy value of the polymer was smaller than approximately 3.59 mJ/m2, generated by the nonpolar isoeugenol moiety with long and bulky carbon groups. Good alignment stability at 100 °C and under ultraviolet (UV) irradiation of 15 J/cm2 was observed for the LC cells fabricated using PIEU100 as a LC alignment layer. Therefore, renewable isoeugenol-based materials can be used to produce an eco-friendly vertical LC alignment system.

scholarly journals Effect of Doping ofCd1−xZnxS/ZnS Core/Shell Quantum Dots in Negative Dielectric Anisotropy Nematic Liquid Crystal p-Methoxybenzylidene p-Decylaniline

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 605
Author(s):  
Ayushi Rastogi ◽  
Fanindra Pandey ◽  
Rajiv Manohar ◽  
Shri Singh
Keyword(s):  
Quantum Dots ◽  
Liquid Crystal ◽  
Dielectric Permittivity ◽  
Nematic Liquid Crystal ◽  
Phase Shifters ◽  
Ion Trapping ◽  
Dielectric Anisotropy ◽  
Core Shell ◽  
Optical Parameters ◽  
Dielectric Parameters

We report the effect of the doping of Cd1−xZnxS/ZnS core/shell quantum dots (CSQDs) in nematic liquid crystal p-methoxybenzylidenep-decylaniline (MBDA) at 0.05 wt/wt%, 0.1 wt/wt%, 0.15 wt/wt%, 0.2 wt/wt%, 0.25 wt/wt%, and 0.3 wt/wt% concentrations of CSQDs in MBDA. Dielectric parameters with and without bias with respect to frequency have been investigated. The change in electro-optical parameters with temperature has also been demonstrated. The increase in the mean dielectric permittivity was found due to the large dipole moment of CSQDs, which impose stronger interactions with the liquid crystal molecules. The dielectric anisotropy changes sign on doping CSQDs in MBDA liquid crystal. It was concluded that the CSQD doping noticeably increased the dielectric permittivity of nematic MBDA in the presence of an electric field. The doping of CSQDs in nematic MBDA liquid crystal reduced the ion screening effect effectively. This phenomenon is attributed to the competition between the generated ionic impurities during the assembling process and the ion trapping effect of the CSQDs. The rotational viscosity of nematic liquid crystal decreased with increasing concentration of the CSQDs, with a faster response time observed for the 0.05 wt/wt% concentration. The birefringence of the doped system increased with the inclusion of CSQDs in MBDA. These results find application in the field of display devices, phase shifters, LC – gratings, TIR waveguide, industries, and projectors.

66.1: High Birefringence and Negative Dielectric Anisotropy Liquid Crystal Mixtures for Vertical Alignment Applications

2009 ◽  
Vol 40 (1) ◽  
pp. 992
Author(s):  
Sebastian Gauza ◽  
Meizi Jiao ◽  
Shin-Tson Wu ◽  
Przemysław Kula ◽  
Roman Dabrowski ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Dielectric Anisotropy ◽  
Vertical Alignment ◽  
High Birefringence

Development of an Optical Fiber Sensor with a D-shaped Fiber Bragg Grating Integrated in a Loop-mirror Optical Fiber Laser as a High Sensitivity Refractometer

2021 ◽  
Vol 32 ◽  
Author(s):  
Binh Pham Thanh ◽  
Thuy Van Nguyen ◽  
Van Hoi Pham ◽  
Huy Bui ◽  
Thi Hong Cam Hoang ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Fiber ◽  
Fiber Laser ◽  
Fiber Bragg Grating ◽  
Limit Of Detection ◽  
Optical Fiber Sensor ◽  
High Sensitivity ◽  
Optical Signal ◽  
Bragg Grating ◽  
Loop Mirror

In this paper, we report a new type of refractometer based on a D-shaped fiber Bragg grating (FBG) integrated in a loop-mirror optical fiber laser. This proposed sensor is used in wavelength interrogation method, in which the D-shaped FBG is applied as a refractive index (RI) sensing probe and a mirror to select mode of laser. The D-shaped FBG is prepared by the removal of a portion of the fiber cladding covering the FBG by means of side-polishing technique. The D-shaped FBG sensing probe integrated in a loop-mirror optical fiber laser with saturated pump technique, the characteristics of sensing signals have been improved to obtain stable intensity, narrower bandwidth and higher optical signal-to-noise ratio compare to normal reflection configuration. The limit of detection (LOD) of this sensor can be achieved to 2.95 x 10-4 RIU in the refractive index (RI) range of 1.42-1.44. Accordingly, we believe that the proposed refractometer has a huge potential for applications in biochemical-sensing technique.

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