Two-dimensional snapshot measurement of surface variation of anchoring in liquid crystal cells

Abstract

Enhanced, photoactive response can be realised by integrating liquid crystals with photoalignment or photoconductive alignment layers. Such cells, asymmetric by design, need to be monitored for the stability and uniformity, especially in the regions exposed to light. In this work, we report on an integrated, versatile model and technique to characterise their core parameters as well as more subtle effects, such as the strength of anchoring energy. The snapshot method also provides twodimensional maps of the cells' thickness, pretilt angle and uniformity.

Nanoparticle-Induced Property Changes in Nematic Liquid Crystals

“…To measure and characterise our samples, we used a CPI setup [ 34 ] consisting of a planar liquid crystal cell placed between two crossed polarisers (polariser and analyser), with the LC director field at an angle of 45° with the axes of polarisers. The cell was illuminated by a laser with a beam area of about 7 mm 2 that defined the studied area of the samples.…”

“…This setup was controlled by a software, which performs data acquisition and analysis [ 34 ]. The cells were addressed with a sinusoidal AC signal at 10 kHz, the amplitude of which varied from 0 to 10 V with a voltage step of 0.02 V. The average value of the CPI was measured at each voltage step.…”

“…With the expanding research on doped LCs, there is an increasing need for a quick and reliable method of quantifying the electro-optical and physical properties of LC composites. In this study, we propose a method to characterise colloidal suspensions using an optical multi-parameter analyser (OMPA), a method originally designed for undoped LCs [ 34 , 35 ]. It measures critical LC properties such as elastics constants (splay elastic constant K 1 and bend elastic constant K 3 ), pretilt θ, anchoring energy W p and rotational viscosity γ 1 from simple cross-polarised intensity experiments (CPI).…”