Light‐Patterned Crystallographic Direction of a Self‐Organized 3D Soft Photonic Crystal

Abstract

Uniform and patterned orientation of a crystallographic direction of ordered materials is of fundamental significance and of great interest for electronic and photonic applications. However, such orientation control is generally complicated and challenging with regard to inorganic and organic crystalline materials due to the occurrence of uncontrollable dislocations or defects. Achieving uniform lattice orientation in frustrated liquid-crystalline phases, like cubic blue phases, is a formidable task. Taming and tailoring the ordering of such soft, cubic lattices along predetermined or desired directions, and even imparting a prescribed pattern on lattice orientation, are more challenging, due to the entropy-domination attribute of soft matter. Herein, we disclose a facile way to realize designed micropatterning of a crystallographic direction of a soft, cubic liquid-crystal superstructure, exhibiting an alternate uniform and random orientation of the lattice crystallographic direction enabled by a photoalignment technique. Because of the rewritable trait of the photoalignment film, the pattern can be erased and rewritten on-demand by light. Such an oriented soft lattice sensitively responds to various external stimuli such as temperature, electric field, and light irradiation. Furthermore, advanced reflective photonic applications are achieved based on the patterned crystallographic orientation of the cubic blue phase, soft lattice.

Patterning of Discotic Liquid Crystals with Tunable Molecular Orientation for Electronic Applications

“…Recently, patterning self‐organized soft matter such as rod‐like liquid crystals and controlling their molecular orientation in the patterns have received enormous attention for their applications in optical vortex generation[19e] and templating molecular self‐assembly. [19f,20] For discotic liquid crystals, it is much more challenging and complicated to simultaneously achieve ordered patterns and macroscopic uniform molecular alignment for applications in molecular conducting wires and integrated circuits. There are a few attempts successfully achieving organized periodic structure with long‐range uniform alignment by incorporating DLCs with anodic aluminum oxide,[15b,c] microchannels,[15d] or nanogrooves.…”

Dynamic Control of Light Direction Enabled by Stimuli‐Responsive Liquid Crystal Gratings

“…Mater. [299] By using a photomask, a BP was polymer stabilized according to desired patterns, resulting in uniformly oriented regions that were exposed to UV light and other regions with random oriented BP, as shown in Figure 25A,B. The bright regions result in higher polymer concentration than the dark region, so the electric field, when applied, has different effects on the director switching process, thus resulting in a periodic arrangement.…”

Light‐Activated Liquid Crystalline Hierarchical Architecture Toward Photonics

“…Copyright 2015, Royal Society of Chemistry. (C) Reproduced with permission . Copyright 2017, Wiley‐VCH.…”

“…On the other aspect, a traditional concept indicates that BPLC is alignment‐free due to its characteristic of optically isotropy, however the photoresponse of the common BPLC which is unnecessary for mixing any other functional additives can be attained readily through the photoalignment technique, which can control the orientation direction and surface anchoring through an irradiation, i.e., the lattice orientation of BP at an exposed area shows homogeneity, whereas the common platelet texture, manifesting a random orientation of lattice, is presented at an unexposed area (Figure C‐I,II) . In virtue of photoalignment, diverse micropatterns with an alternate area of uniform/random orientation of BP lattice, including the straight stripes, squares, fork‐like stripes, and even more complicated structures (Figure C‐III–VI), were formed, and moreover, these patterns were photorewritable due to the feature of photoalignment film.…”