The generality of mussel-inspired dopamine-melanin (DM) deposition at the solid-solution interface has generated a lot of interest in the scientific community in the last decade. Even though the adhesion mechanism has been elusive, dopamine oxidation and the formation of aggregates held together by covalent bonding, π-π stacking, charge transfer and/or hydrogen bonding have been implicated. The interaction between the dopamine-melanin layer and the underlying substrate, however, is not at all well understood. In this research, dopamine adsorption was carried out on a range of substrates from native silicon wafer (Si-OH) to silicon wafers containing covalently attached polydimethylsiloxane (Si-PDMS), amine-functionalized PDMS (Si-PDMS-NH<sub>2</sub>), and thiol-functionalized PDMS (Si-PDMS-SH). We hypothesize that the DM layer interacts primarily with Si-OH via hydrogen bonding, with PDMS via hydrophobic interactions, and with PDMS-NH<sub>2</sub> and PDMS-SH via hydrophobic interactions and covalent bonding. The DM growth kinetics on these substrates and the stability of the DM films in acid, base, and organic solvents were examined. AFM images of the DM film growth kinetics on Si-OH and Si-PDMS show distinctly different adhesion and growth mechanisms. Full characterization using dynamic water contact angles, ellipsometric thickness, and AFM imaging will help elucidate the effects of surface chemistry and energetics on dopamine adhesion mechanisms and DM thin film stability.

Elucidating dopamine adhesion via surface chemistry

254th National Meeting (2017)

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