Functionalization of cycloolefin polymer surfaces by plasma-enhanced chemical vapour deposition: comprehensive characterization and analysis of the contact surface and the bulk of aminosiloxane coatings

The surface science of bioassay devices is of great importance in the development of modern diagnostic platforms. The quality of surface is one of the most important elements of the device, often governing the background response, hence controlling the sensitivity of an assay. Detailed surface characterization and analysis are imperative for the preparation of reproducible coatings with desired properties. We performed a comprehensive characterization of 3-aminopropyl-triethoxysilane films prepared under two different deposition conditions on COP slides. Two sets of slides were prepared, by exposing them to plasma reaction for 30 seconds (A30 slide) and 4 minutes (A4 slide). While the variations in the deposition conditions seemed very subtle, the use of several powerful analytical tools helped us to reveal some fundamental differences between the studied films in terms of binding capacity, swelling and adhesion. Overall, the A30 films, with a thickness of 5.12 nm, showed up to 40% higher binding capacity and 25% better adhesion than the thicker A4 coatings (28.15 nm). Upon contact with aqueous media, a significant change was observed in terms of surface roughness. The A30 slides outperformed A4 slides, resulting in smoother surface, which is an important parameter for biomolecule immobilisation. The use of the techniques described in this article is aimed to set new standards for the characterization and analysis of the substrate surface of the future diagnostic devices.