Comparative Investigation of Substrate Effects on the Surface Free Energy of Self-Assembled Monolayers on Au, TiO 2 , and Al 2 O 3

Self-assembled monolayers (SAMs) are widely used to tailor surface properties of biomaterials and implant surfaces. In this study, the influence of the underlying substrate on the apparent surface properties despite the presence of a SAM coating is investigated. Structurally analogous thiol- and phosphonate-based monolayers were formed on gold, titanium dioxide and aluminum oxide surfaces. Surface free energies were determined using contact angle measurements. The results indicate that the measured surface free energy can still depend on the substrate material despite the presence of a SAM coating.