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Seminar | Nanoscience and Technology Division

Directed Self-Assembly of Blue-Phase Liquid Crystals by Chemically Patterned Surfaces

NST Seminar

Abstract: Liquid crystals (LCs) are a matter state intermediate between the solid and liquid phases. The unique properties of LCs, such as inherent ordering as liquid phase, optical anisotropy, and ability to respond to an external field, make them widely used for electronic displays, laser devices, photonics, biosensors, and metastructures. A fundamental understanding of the morphology and through-film optical properties of the LC system, as well as precisely controlling the orientation of LC molecules toward contacting surfaces, plays a central role in device design and performance.

In this seminar, I will present a generalizable platform based on anchoring contrast from chemically patterned surfaces to a directed self-assembly (DSA) LC system. I will concentrate on a chiral nematic system for more complex LC morphologies and behaviors. More specifically, I will focus on blue-phase (BP) LCs, which exhibit ordered cubic arrangements of topological defects. The highly ordered morphology of BPs gives rise to unusual physical properties, such as Bragg reflection of visible light and fast optical response. However, their polycrystalline structures limit their performance in applications.

Chemically patterned surfaces are presented for the first time to obtain stable, lattice selective, macroscopic single-crystal BP materials. By studying the chemical pattern assisted heterogeneous crystal nucleation and the growth process of BPs, the transformation between BPs is found to be martensitic in nature as the result of the collective behavior of the double-twist cylinders.

I will conclude by discussing some of the potential application of these materials, along with the questions and challenges remaining in the field.