Heptatic liquid quasi-crystals by colloidal lithographic pre-assembly

Tianren Yu; Thomas G Mason

doi:10.1016/j.jcis.2023.12.157

Heptatic liquid quasi-crystals by colloidal lithographic pre-assembly

J Colloid Interface Sci. 2024 Jul:665:535-544. doi: 10.1016/j.jcis.2023.12.157. Epub 2023 Dec 31.

Authors

Tianren Yu¹, Thomas G Mason²

Affiliations

¹ Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, USA.
² Department of Chemistry and Biochemistry, University of California-Los Angeles, Los Angeles, CA 90095, USA; Department of Physics and Astronomy, University of California-Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California-Los Angeles, Los Angeles, CA 90095, USA. Electronic address: mason@chem.ucla.edu.

PMID: 38538483
DOI: 10.1016/j.jcis.2023.12.157

Abstract

Hypothesis: We hypothesize that pre-assembled lithographic Brownian seven-fold quasi-crystals (QCs) of colloidal tiles at high densities can exhibit a heptatic liquid quasi-crystal (LQC) phase upon release; such heptatic LQCs can undergo heterogeneous dynamics at different length scales, reflecting the underlying symmetry, corrugation, and hierarchy of local sets of tiles.

Experiments: We design, fabricate, and release a seven-fold QC composed of three differently shaped rhombic tiles using the method of lithographically pre-assembled monolayers (litho-PAMs). High resolution optical microscopy enables spatio-temporal particle tracking of Brownian fluctuations of many tiles in a large area over a long time. We develop an edge-proximity tessellation method for analyzing nearest neighboring particles that can be applied to assemblies and dense systems of complex shapes.

Findings: A fluctuating heptatic LQC phase is identified at high tile area fractions. Heterogenous dynamics and order at different length scales indicate diverse, hierarchical motif structures. We show that certain motifs can collectively rotate without any cage breaking, leading to alterations of the local tile-structure reminiscent of phason-flips in atomic QCs; this rotation causes a slow decline in the system's spatial order. We anticipate that edge-proximity tessellation will help elucidate phase transitions of other systems made of diverse building blocks having significant geometrical complexity at multiple length scales.

Keywords: Heptatic phase; Heterogeneous dynamics; Liquid crystal; Lithography; Quasi-crystal.