High-quality alignment of nematic liquid crystals using periodic nanostructures created by nonlinear laser lithography

• Published in: Journal of molecular liquids 2018-10, Vol.267, p.212-221
• Main Authors: Pavlov, I.A., Rybak, A.S., Dobrovolskiy, A.M., Kadan, V.M., Blonskiy, I.V., Kazantseva, Z.I., Gvozdovskyy, I.A.
• Format: Article
• Language: English
• Subjects: Aligning layers; Azimuthal anchoring energy; Nanostructured titanium layers; Nematic liquid crystals; Nonlinear laser lithography; Polyimide
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.02.058

It is well known that today two main and well studied methods for alignment of liquid crystals has been used, namely: rubbing and photoalignment technologies, that lead to the change of anisotropic properties of aligning layers and long-range interaction of the liquid crystal molecules in a mesophase. In this manuscript, we use the nonlinear laser lithography technique, which was recently presented as a fast, relatively low-cost method for a large area micro and nanogrooves fabrication based on laser-induced periodic surface structuring, as a new perspective method of the alignment of nematic liquid crystals. 920nm periodic grooves were formed on a Ti layer processed by means of the nonlinear laser lithography and studied as an aligning layer. Aligning properties of the periodic structures of Ti layers were examined by using a combined twist LC cell. In addition, the layer of the nanostructured Ti was coated with an oxidianiline-polyimide film with annealing of the polymer film followed without any further processing. The dependence of the twist angle of LC cells on a scanning speed and power of laser beam during processing of the Ti layer was studied. The azimuthal anchoring energy of Ti layers with a periodic nanostructure was calculated. The maximum azimuthal anchoring energy for the nanostructured Ti layer was about 4.6×10−6J/m2, which is comparable to the photoalignment technology. It was found that after the deposition of a polyimide film on the periodic nanostructured Ti layer, the gain effect of the azimuthal anchoring energy to ~1×10−4J/m2 is observed. Also, AFM study of aligning surfaces was carried out. [Display omitted] •Nanostructured titanium (Ti) layer and nanostructured Ti layer coated with polymer as aligning surfaces were studied.•Nanostructured Ti layers were fabricated by a fast, relatively low-cost technique nonlinear laser lithography (NLL).•Azimuthal anchoring energy structured Ti layers depends on NLL parameters (laser power and scanning speed).•Nanostructured Ti layer possesses a weak anchoring energy.•The dramatic increase in azimuthal anchoring energy value for the structured Ti layer coated with polymer was found.