High Resolution Imaging of Nonequilibrium Colloidal Self-Assembly via Photofixation

Year: 2026

Type: article

Abstract: The self-organization of colloidal nanoparticles into complex structures, both in equilibrium and out-of-equilibrium, is a growing area in colloidal science with potential for creating functional materials. While equilibrium assemblies form stable and periodic structures, out-of-equilibrium (or active) assemblies exhibit dynamic, reconfigurable behavior under external stimuli. Therefore, understanding the structure-function relationships in these assemblies remains challenging due to their transient nature and limitations of current characterization methods. In this work, we present a methodology termed Fixation and Resolving of Colloidal Active Matter Ensembles (FRAME). FRAME combines UV photopolymerization to fix nonequilibrium colloidal assemblies with high-resolution imaging techniques, including 3D confocal microscopy, SEM and 3D STED super-resolution imaging, for subsequent structural characterization. We applied this method to Optical Matter (OM) structures formed within an optical trap at the glass/water interface. Using FRAME, we conducted a detailed analysis of OM structures composed of colloidal nanoparticles ranging from 200 nm to 1 μm. We demonstrate the robustness of this method by validating that the fixation process does not alter structural properties, allowing for accurate structural analysis. FRAME offers a distinct approach for investigating nonequilibrium colloidal assemblies, enabling the way for their rational design and application across a broad range of colloidal systems.

Source: ACS Nano

DOI: 10.1021/acsnano.5c22002

Authors: Jagannath Satpathy, Jim Jui-Kai Chen, Gang Wen, Hiroshi Masuhara, Sudipta Seth, Volker Leen, Susana Rocha, Johan Hofkens, Boris Louis, Roger Bresolí-Obach

Institutions: KU Leuven, University of Würzburg, National Yang Ming Chiao Tung University, Max Planck Institute for Polymer Research, Institut Químic de Sarrià, Universitat Ramon Llull

Language: English

Topic: Orbital Angular Momentum in Optics

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: European Commission, Shanghai Educational Development Foundation, Fonds Wetenschappelijk Onderzoek, Ministry of Science and Technology, KU Leuven, Ministry of Education, India, Vlaamse regering, National Science and Technology Council, HORIZON EUROPE Framework Programme, European Regional Development Fund, Agencia Estatal de Investigación, H2020 Marie Skłodowska-Curie Actions, National Yang Ming Chiao Tung University

OpenAlex ID: W7128721768