Abstract: The invention relates to methods of controlling orientation of direct covalent binding of a peptide to a polymer substrate surface, to surfaces with peptides directly covalently bound thereto in a manner where the orientation of binding is controlled as well as to devices comprising such substrates. In particular the invention relates to A method of controlling predominant orientation of direct covalent binding of one or more peptides to a polymer substrate surface comprising: (a) exposing the surface to energetic ion treatment to generate a plurality of activated sites comprising reactive radical species; (b) incubating the surface with one or more peptide/s that exhibit or can be induced to exhibit a dipole moment and manipulating the electric field environment and/or charge of said surface and/or of said peptide/s during said incubating; wherein predominant orientation of direct covalent binding of said peptide/s to said surface is thereby controlled.