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Description:

The assembled structures of melanin particles, i.e., colloidal particles coated with a melanin-like polydopamine (PDA) layer, create vivid structural colors. While the thickness of the PDA layer influences the particle arrangement and optical properties, the underlying mechanism has remained controversial. We demonstrate that the water-swelling characteristics of PDA are crucial factors governing the dispersion and aggregation of these particles in solution. Detailed comparisons between dry and wet conditions revealed that the PDA layer readily absorbs water molecules, which leads to significant swelling in the thicker layers. The swelling of the PDA layers determined whether the particles remained dispersed or partially aggregated in the water, ultimately controlling the particle arrangement in the dry state once the water evaporated. These findings provide insights into the self-assembly of colloidal particles and offer a strategy for tuning the periodic particle order. This feature is pivotal for various applications in optical and sensing technologies.

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  This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, copyright © 2025 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.langmuir.5c01855.

Keyword: polydopamine, structural colors, colloidal crystal, core shell, amorphous, Bragg diffraction, iridescent

Date published: 2025-09-02

Publisher: American Chemical Society (ACS)

Journal:

• Langmuir (ISSN: 07437463) vol. 41 issue. 34 p. 22762-22773

Funding:

• Japan Society for the Promotion of Science JP24H01697
• Japan Society for the Promotion of Science JP23H02018
• National Institute for Materials Science 2024-042
• National Institute for Materials Science 2025-011
• Support for Pioneering Research Initiated by the Next Generation J24HJ00045

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5915

First published URL: https://doi.org/10.1021/acs.langmuir.5c01855

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Updated at: 2026-02-14 20:51:38 +0900

Published on MDR: 2026-08-21 08:25:49 +0900