Abstract: A method of producing a microfluidic device having at least one flow path may include providing a base substrate with a first surface and a top substrate with a second surface, hydrophilically treating at least one of the first and the second surfaces to provide a surface layer with a higher surface tension than the surface tension prior to the hydrophilic treatment, partly or totally removing the surface layer with a higher surface tension in a selected pattern of the hydrophilically treated first and/or second surfaces, to thereby provide the selected pattern with a lower surface tension than prior to the partly or totally removal of the surface layer with a higher surface tension in said selected pattern of the hydrophilic treated first and/or second surfaces, and joining said base substrate and top substrate to each other to provide a flow path between said first and second surfaces.