Polarized microscopy

The homeotropic film was checked on orientation and eventual defects by polarized microscopy (Leica). The alternating electric field with the sinoidal wave function is provided by the function generator (AFG3252C, Tektronix). The electric signal from the function generator is amplified through an amplifier (F20A, FCL electronics). The output voltage is measured by an oscilloscope (DSOX3032 T, Keysight). The surface topographies are measured by Digital Holography Microscopy (Lyncée Tec SA.).

The liquid crystal (LC) mixture was filled between two glass plates provided with the alignment layer by capillary suction. The sample was cured at 36 °C by ultraviolet exposure for 5 min with an intensity of 400 mW cm⁻² using a mercury lamp (Exfo Omnicure S2000) equipped with a cutoff filter transmitting light >400 nm (Newport FSQ-GG400 filter). The samples were postbaked at 120 °C under N₂ to ensure full conversion of the acrylate monomers. The thickness of the final polymer coating is 5 μm. The cholesteric film was checked by polarized microscopy (Leica). A LED lamp (Thorlab, M365L2 and M455L3) is used to provide monochromatic light. The surface topography is measured using an interference microscopy (Fogal Nanotech Zoomsurf).

The cholesteric film was checked by polarized microscopy (Leica). The mechanical properties of the films are tested by DMTA (Q800 Dynamic Mechanical Analyzer from TA Instruments) at the frequency of 0.5. For this a sample of 14 × 4.2 × 0.06 mm dimensions was fixed at both ends in DMTA clamps and characterized in a strain-controlled mode. The measurements of photomechanical properties are carried out under continuous light illumination. LED lamps (Thorlab, M365L2 and M455L3) are used to provide monochromatic light. Temperature is monitored in a contact way using a thermal couple (Fluke, 80PK-1 K-Type Bead Thermocouple) and in a contactless way using an infrared camera (Fluke Ti-32).