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Spontaneous wrinkle emergence in nascent eumelanin thin films

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Abstract

Self-patterning processes originated by physical stimuli have been extensively documented in thin films, whereas spontaneous wrinkling phenomena due to chemical transformation processes are, to the best of our knowledge, unprecedented. Herein we report a case of spontaneous polymerization-driven surface nano-patterning (∼500 nm) that develops in smooth thin solid films of 5,6-dihydroxyindole (DHI), a major precursor of eumelanin polymers, over a time scale of 30 to 60 days in air at room temperature. The phenomenon can be observed only above a critical film thickness of ∼250 nm and it is affected by exposure to ammonia vapors causing acceleration of the oxidation process. The thickness-dependent onset of wrinkling can be attributed to non-homogeneous rates of oxidation through the film causing slow swelling/expansion of the inner layers followed by fast stiffening and cross-linking in the outer layer exposed to higher oxygen levels.

Graphical abstract: Spontaneous wrinkle emergence in nascent eumelanin thin films

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Publication details

The article was received on 17 Sep 2019, accepted on 17 Oct 2019 and first published on 18 Oct 2019


Article type: Paper
DOI: 10.1039/C9SM01885A
Soft Matter, 2019, Advance Article

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    Spontaneous wrinkle emergence in nascent eumelanin thin films

    S. L. Oscurato, F. Formisano, C. de Lisio, M. d'Ischia, F. Gesuele, P. Maddalena, P. Manini, L. Migliaccio and A. Pezzella, Soft Matter, 2019, Advance Article , DOI: 10.1039/C9SM01885A

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