Plasma enhanced chemical vapour deposition was investigated for the deposition of biofunctional thin films onto surfaces in the fabrication of biomedical diagnostic devices. Two major aspects of the deposited films were assessed for their applicability in new diagnostic systems. The first relates to the functionality of the surface. The functionality of the surface relates to the ability of specific surface functional groups to be deposited stably and in a manner that will allow for biomolecular adhesion. Biomolecular adhesion is an important feature of surfaces requiring immobilisation of a detection agent, especially in liquid throughput devices. A comprehensive characterisation of the films developed herein was carried out. Following on from work previously undertaken by members of our research group, the films developed have shown a high degree of stability of the density of surface functional groups after exposure to aqueous conditions similar to those employed by liquid throughput devices. I found that the densities of these surface groups are superior to films created through liquid chemical deposition. Processes developed as part of this work were tailored for optimal manufacturability, e.g. the removal of heating apparatus required by the aminopropyltriethoxysilane monomer by installing a complimentary tetraethyl orthosilicate and allylamine process. Secondly, I investigated surface wettability and developed a novel process for surface wettability control using atetraethyl orthosilicate and acrylic acid film stack. The plasma polymerised acrylic acid film was employed to react with the underlying organosilicon matrix, causing a shift in the surface characteristics. The polymeric acrylic acid network was shown to have a wearing effect on the organosilicon, catalysed by environmental water vapour. This process was subsequently controlled for the purpose of wettability control of the surface. As the underlying organosilicon layer is reduced, the increasingly oxygen rich interface becomes more hydrophilic, giving specific and stable control over the surfaces‟ water contact angle. As the fluidic interaction with a surface is generally of high importance in microfluidics, control of this provides a method of improving the workability of novel fluidic systems with materials that previously showed unfavourable characteristics.