Deposition penetration depth and sticking probability in plasma polymerization of cyclopropylamine
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Understanding the role of substrate geometry is vital for a successful optimization of low-pressure plasma polymerization on non-planar substrates used in bioapplications, such as porous materials or well plates. We investigated the altered transport of film-forming species and properties of the coatings for a cyclopropylamine and argon discharge using a combined analysis of the plasma polymer deposition on flat Si pieces, culture wells, microtrenches, a macrocavity, porous hydroxyapatite scaffolds and electrospun polycaprolactone nanofibrous mats. The aspect ratio of the well structures impacted mainly the deposition rate, whereas the film chemistry was affected only moderately. A large deposition penetration depth into the porous media indicated a relatively low sticking probability of film-forming species. A detailed analysis of microtrench step coverage and macrocavity deposition disproved the model of film-forming species with a single overall sticking probability. At least two populations with two different sticking probabilities were required to fit the experimental data. A majority of the film-forming species (76%) has a large sticking probability of 0.20 +/- 0.01, while still a significant part (24%) has a relatively small sticking probability of 0.0015 +/- 0.0002. The presented methodology is widely applicable for understanding the details of plasma-surface interaction and successful applications of plasma polymerization onto complex substrates.
KeywordsPlasma polymerization, 3D structured substrates, Bioactive functional coating, Penetration depth, Sticking probability
Document typePeer reviewed
Document versionFinal PDF
SourceAPPLIED SURFACE SCIENCE. 2021, vol. 540, issue 1, p. 1-10.