Surface and Tribological Behaviors of the Bioinspired Polydopamine Thin Films under Dry and Wet Conditions

Abstract

Dopamine is a "sticky" biomolecule containing the typical functional groups of mussel adhesive proteins. It can self-polymerize into a nanoscale thin film on various surfaces. We investigated the surface, adhesion, friction, and cracking properties of polydopamine (PDA) thin films for their effective transfer to functional devices and biocompatible coatings. A series of surface characterizations and mechanical tests were performed to reveal the static and dynamic properties of PDA films coated on glass, polydimethylsiloxane (PDMS), and epoxy. We found that PDA films are highly hydrated under wet conditions because of their porous membrane-like nanostructures and hydrophilic functional groups. Upon dehydration, the films form cracks when they are coated on soft substrates due to internal stresses and the large mismatch in elastic modulus. The adhesive pull-off force or the effective work of adhesion increased with the contact time, suggesting dynamic interactions at the interface. A significant decrease in friction forces in water was observed on all three material surfaces coated with PDA; thus, the film might serve as a water-based lubrication coating. We attributed the different behavior of PDA films in air and in water to its hydration effects. These research findings provide insight into the stability, mechanical, and adhesive properties of the PDA films, which are critical for their applications.

Formation of silica colloidal crystals on soft hydrophobic vs rigid hydrophilic surfaces

“…1C, the colloidal crystals stayed on the PDMS surface regardless of the silica concentrations, indicating strong adhesion to the substrate [24]. To characterize the adhesion force between silica NPs and polymer substrate, we tried the peeling adhesion test with the tape/NPs/substrate system [25], but failed due to the weak internal adhesion between the SiO 2 NPs. When applying the tape on the sample, part of the silica colloidal crystals stuck to the tape, while the other part stayed on the substrate after peeling, suggesting that failure first occurred at the interface of NPs/NPs for all samples.…”

Preparation and Layer-by-Layer Solution Deposition of Cu(In,Ga)O2 Nanoparticles with Conversion to Cu(In,Ga)S2 Films

“…PDA is a strong adhesive [50], [51] produced by polymerization of dopamine under basic pH conditions and used by marine organisms such as mussels to anchor themselves to solid surfaces in underwater environments. [52], [53] Although its composition and structure remain uncertain, electrostatic and covalent interactions involving both the amine and catechol sites of dopamine have been identified within PDA.…”

Dopamine‐Based Coatings and Hydrogels: Toward Substitution‐Related Structure–Property Relationships

“…A silica-coated crystal was used (Q-Sense, Sweden). The crystal was excited at its fundamental frequency (5 MHz), and measurements of the frequency and dissipation change ( Δf, ΔD ) were performed at the fi rst, third, fi fth, seventh, ninth, and thirteen overtones, corresponding to 5,15,25,35,45, and 55 MHz, respectively. The displayed graphs correspond to the third overtone, unless otherwise stated.…”

“…[ 2,[4][5][6] The catechol group of DOPA is amenable to oxidation, self-coupling, and nucleophilic attack when it comes in contact with salt water, and it can interact with inorganic cations via cation-π interactions or forming stable complexes. These reactions lead to crosslinking of the mussel adhesive proteins, solidifi cation of the glue, as well as strong attachment to the rocks.Harnessing on catecholamines' characteristic behavior, highly adhesive biocompatible coatings for the functionalization of organic and inorganic substrates [7][8][9][10][11][12][13][14][15][16] and particles [17][18][19][20] have been reported from dopamine (Dop), norepinephrine (NE), and gallolamine. [ 21 ] Incubation of the reactive polycatechol layer with different ligands [ 9 ] or codeposition of nucleophiles during the coating process [ 22 ] allowed moreover modifi cation and extension of coating functionality.…”