The University of Science and Technology of China has made important progress in the field of topological structure of active substances

Professor Peng Chenhui's team from the Department of Physics at the University of Science and Technology of China has made important progress in the topological transformation of optically controlled active substances. In recent ten years, the study of active soft matter has gradually become the research frontier of soft condensed matter physics. How to analyze topological structures such as topological defects, solitons and vortices is the key to understanding active soft matter in non-equilibrium state. Due to the inherent non-equilibrium properties of active soft matter and its complex three-dimensional structure, the study of its topological structure has always been a challenge and an opportunity. In collaboration with Professor Peng Chenhui from HKUST and Professor Zhang Rui from HKUST, a programmable 3D topological structure has been prepared using optical configuration method based on anisotropic liquid crystal materials. The work was recently published in the Proceedings of the National Academy of Sciences under the title "Active transformations of topological structures in light-driven nematic disclination networks."

Liquid crystal is a kind of material whose molecular orientation is long ordered. Liquid crystal molecules can self-assemble into certain structures, and are widely used in display, induction, photonic devices and other fields. The research team first prepared the two-dimensional topology defect by controlling the self-assembled structure of the liquid crystal, and then combined the two-dimensional topology pattern with the liquid crystal molecule in a specific direction, taking advantage of the incompatibility between the two configurations to prepare the three-dimensional topology in equilibrium. Then, the liquid crystal molecules are driven by light to make them in a non-equilibrium state and become an active soft matter system, so as to realize the mutual conversion between the three-dimensional topologies. Since the 2D topological patterns that form the 3D topologies are predesignable throughout the process, the research team was able to programmatically control the transformation between different 3D topologies (as shown in Figure 1). By placing biomolecules in this three-dimensional topology, the biomolecules self-assemble at the topological defect array (as shown in Figure 1) without the need for any external forces or fields. The 3D topological defect array is completely determined by the optical configuration and can be duplicated by the optical field. Reproducible 3D topological defects are guided by light fields to produce different orientations, positions, and geometric patterns. The programmable 3D topology can induce the biomolecular self-assembly on it to change with it, so as to realize the optically controlled programmable biomolecular self-assembly function.

Reviewers give high praise to this work: "This is a very nice work demonstrating a significant advance in the dynamical control. This is a very nice work demonstrating a significant advance in the dynamical control of disclination lines in nematic liquid crystals.) ".

Figure 1. 3D topology formed by controlling liquid crystal configuration

In this work, 3D topologies of soft matter in non-equilibrium state are prepared for the first time, and the 3D topologies are converted into each other in a programmable way by using illumination. This fundamental research will help us understand the three-dimensional topology in active soft matter. The programming of topologies by controlling molecular self-assembly used in this work provides a broad space for future research on programmable biomolecular self-assembly and intelligent active materials.

Chenhui Peng from HKUST and Rui Zhang from HKUST are co-corresponding authors, Jinghua Jiang from HKUST, Kamal Ranabhat from the University of Memphis and Xinyu Wang from HKUST are co-first authors.

Thesis information:

Active transformations of topological structures in light-driven nematic disclination networks

https://www.pnas.org/doi/10.1073/pnas.2122226119

(Department of Physics, Department of Scientific Research)

Source: HKUST News Network