A novel process for local surface fluorination of polymer surfaces is being introduced. The process allows a local adjustment of the surface energy and hence the contact angle of liquids on polymer surfaces. With this technology, surfaces with altered water contact angle for biomedical applications can be manufactured in a single process step from bulk polymer plates. The process is based on a UV-dissociable fluorine containing precursor (1,2,3,5-Tetrafluorobenzene). The employed UV-laser was a KrF laser emitting UV-photons with a wavelength of 248 nm (5 eV). As a bulk polymer, polystyrene was used. The UV-photons dissociate the precursor producing fluorine containing radicals. For the process, the polymer sample is placed inside a vacuum chamber in which the precursor is put in gaseous state. The laser radiation enters the chamber via a calcium fluoride window. In order to achieve a short and efficient fluorination process, several process parameters (UV pulse fluence, accumulated UV fluence and precursor pressure / density) have been investigated. The results have been used as an experimental basis for an analytical model, which describes the ongoing processes of UV-photodissociation, movement of the radicals and possible reactions of the radicals including the reaction with the polymer surface. With optimized fluorination parameters, the effects and the process boundaries of a local fluorination were studied. A slit aperture and a polka dot shadow mask were imaged onto the sample surfaces. XPS measurements have shown that a fluorine content of up to 30 % of the surface can be reached. Smallest structures achievable are smaller than 1 mm.
