Optical properties of nematic liquid crystal (C₂₁H₂₇NO₂S) under AC/DC electric fields

Abstract

In this study, the effects of the phase transition on the optical transmittance of the nematic liquid crystal C21H27NO2S, 4′-isothiocyanatophenyl-4-pentylbicyclo[2,2,2]octane-1-carboxylate are investigated in terms of temperature variation and rotational angle of the polarizer through electro-optical methods under AC / DC electric fields. It is observed that the domain structure of the material is affected considerably by the applied electric field as the temperature changes. Under applied electric fields, the crystal-nematic (CN) phase-transition point changes and the behaviour of the liquid crystal in the phase-transition region shows some differences. The intensity of the light passing through the system under a DC electric field increases as the electric field rises. Nevertheless, the intensity of the transmitted light under an AC electric field increases at the beginning and then decreases as the electric field rises to a temperature of more than 355 K. These results can be explained through the formation of a domain structure during the phase-transition process and the light scattering caused by these structures.

Tunable, Low–Cost, Multi–Channel, Broadband Liquid Crystal Shutter for Fluorescence Imaging in Widefield Microscopy

“…The activation voltage (up to 75 V) of the current LC shutter was relatively high, which can be further improved in the future by reducing the overall thickness of the fluidic chamber and trying different LC materials. Converting the electrical drive input from direct current (DC) to alternating current (AC) can also effectively reduce the activation voltage by 50% under the same transmittance [35]. We expect that the introduced NLC material and shutter design can be applied to wide-field microscopy and bio-optical fields as well as many other applications.…”

Optical Properties of Aligned Nematic Liquid Crystals in Electric Field

“…While there are no external alignment effects, there are randomly oriented domains in the nematic phase. However, if the domain walls of the liquid crystal are processed with known methods, the nematic liquid crystals will have the homogeneous single alignment [9,10]. The electrooptical effects in the LCs may be caused by two different physical processes: 1) the external electric field changes the orientation of molecules causing the absorption and scattering spectrum intensity, 2) the electric field changes the distances between energy levels of the molecule, shifts the absorption bands and varies the transition intensities.…”

“…In this study, the photolithography method was used to providing the micropatterns on the polyimide surface that includes the spin-coating, the UV exposure and the wet chemical etching, respectively. By taking into account the mentioned properties of NLCs, the optical and the electrooptical properties of randomly [9] and aligned NLCs are examined in the temperature range including phase transitions.…”