Curvature-driven, One-step Assembly of Reconfigurable Smectic Liquid Crystal "Compound Eye" Lenses

TL;DR

This paper presents a novel one-step method to self-assemble reconfigurable smectic liquid crystal 'compound eye' lenses with variable focal lengths and polarization sensitivity, mimicking biological invertebrate eyes for advanced optical applications.

Contribution

It introduces a curvature-driven self-assembly technique for hierarchical smectic LC lenses that can be reconfigured and tuned in real-time, a significant advancement over previous multi-step fabrication methods.

Findings

Hierarchical 'flower pattern' lenses mimic compound eyes.

Focal length varies from a few to tens of microns within a single structure.

Lenses can construct 3D images and are reconfigurable via temperature.

Abstract

Confined smectic A liquid crystals (SmA LCs) form topological defects called focal conic domains (FCDs) that focus light as gradient-index lenses. Here, we exploit surface curvature to self-assemble FCDs in a single step into a hierarchical structure (coined "flower pattern") molded by the fluid interface that is pinned at the top of a micropillar. The structure resembles the compound eyes of some invertebrates, which consist of hundreds of microlenses on a curved interface, able to focus and construct images in three dimensions. Here we demonstrate that these flowers are indeed "compound eyes" with important features which have not been demonstrated previously in the literature. The eccentric FCDs gradually change in size with radial distance from the edge of the micropillar, resulting in a variable microlens focal length that ranges from a few microns to a few tens of microns within a single "flower". We show that the microlenses can construct a composite 3D image from different depth of field. Moreover, the smectic "compound eye" can be reconfigured by heating and cooling at the LC phase transition temperature; its field of view can be manipulated by tuning the curvature of the LC interface, and the lenses are sensitive to light polarization.