Nonlinear laser lithography as a new technology for the high-quality alignment of nematic liquid crystals

TL;DR

This paper introduces nonlinear laser lithography as a novel, efficient method for creating micro- and nanogrooves on titanium layers to align nematic liquid crystals, offering a promising alternative to traditional techniques.

Contribution

It demonstrates the use of nonlinear laser lithography for fabricating microstructured Ti layers that effectively align liquid crystals, with comparable anchoring energy to existing photoalignment methods.

Findings

Microstructured Ti layers achieve azimuthal anchoring energy up to 4.6×10⁻⁶ J/m².

Polyimide coating enhances the anchoring energy to approximately 1×10⁻⁴ J/m².

Laser processing parameters influence the alignment properties of liquid crystals.

Abstract

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 propose the usage of 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. 920 nm 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 microstructured 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 microstructure was calculated. The maximum azimuthal anchoring energy for the microstructured Ti layer was about 4.6*10-6 J/m2, which is comparable to the photoalignment technology. It was found that after the deposition of a polyimide film on the periodic microstructured Ti layer, the gain effect of the azimuthal anchoring energy to ~ 1*10-4 J/m2 is observed. Also, AFM study of aligning surfaces was carried out.