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Experimental approach
This protocol is extracted from research article:
Electrically turning periodic structures in cholesteric layer with conical–planar boundary conditions
Sci Rep, Apr 16, 2021;

Procedure

The test samples are sandwich-like cells consisting of two glass substrates with transparent ITO electrodes coated with polymer films38,39 (Fig. 1a). The bottom substrate was covered with the polyvinyl alcohol (PVA) (Sigma Aldrich) film and then it was unidirectionally rubbed. The top substrate was covered with the poly(isobutyl methacrylate) (PiBMA) (Sigma Aldrich) film without additional treatment after the deposition process. The spin coating method was used to deposit the polymer films on the substrates. ITO layer on the top substrate was etched as the square ($2×2$ $mm2$) areas oriented at the different $α$ angles to the rubbing direction $R$ (Fig. 1a). The values of angles formed by each of the square sides are indicated in Fig. 1a.

The CLC layer thickness $d=5.0μ$m specified by the microspheres was measured by the interference method with spectrometer HR4000 (Ocean Optics) before the filling process. The nematic mixture LN-396 (Belarusian State Technological University) doped with cholesteryl acetate (Sigma Aldrich) was used as CLC. The cells were filled by the CLC in the mesophase at room temperature. After the filling process, the cells were kept for at least 24 h before measurements. The quantity of chiral additive was chosen to obtain the confinement ratio $d/p0=0.6$. The experimental study of the sample was carried out using the polarizing optical microscope (POM) Axio Imager.A1m (Carl Zeiss). An AC voltage of 1 kHz frequency and variable amplitude were applied to the sample from signal generator AHP-3122 (Aktakom).

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