Tunability of Self-Organized Structures Based on Thermodynamic Flux

• Published in: Langmuir 2022-09, Vol.38 (37), p.11330-11336
• Main Authors: Nabika, Hideki, Tsukada, Kanta, Itatani, Masaki, Ban, Takahiko
• Format: Article
• Language: English
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/acs.langmuir.2c01602

Nature establishes structures and functions via self-organization of constituents, including ions, molecules, and particles. Understanding the selection rule that determines the self-organized structure formed from many possible alternatives is fundamentally and technologically important. In this study, the selection rule for the self-organization associated with a reaction–diffusion system was explored using the Liesegang phenomenon, by which a periodic precipitation pattern is formed as a model system. Experiments were conducted by systematically changing the mass flux. At low mass fluxes, a vertically periodic pattern was formed, whereas at high mass fluxes, a horizontally periodic pattern was formed. The results inferred that a structural vertical-to-horizontal periodicity transition occurred in the self-organized periodic structure at the crossover flux at which the entropy production rate reversed. Numerical analyses attributed the as-observed flux-dependent structural transition to the selection of the self-organized pattern with a higher entropy production rate. These findings contribute to our understanding of how nature controls self-organized structures and geometry, potentially facilitating the development of novel designs, syntheses, and fabrication processes for well-controlled organized functional structures.