Application possibilities and chemical origin of sub-micrometer adhesion modulation on polymer gratings produced by UV laser illumination

Sub-micrometer periodic structures were prepared on the surface of poly-carbonate films by UV laser treatment methods: a) grating-like structures having a period of 156 nm were induced by ArF excimer laser, b) 416 nm and 833 nm periodic gratings were prepared by two-beam interference realized by the fourth harmonic of a Nd:Yag laser. The sub-micrometer adhesion pattern accompanying the topographical structure was determined by pulsed force mode atomic force microscopy. The difference between the measured adhesion modulation and the adhesion profile calculated based on the topography was explained by the UV laser illumination caused phase and chemical changes. XPS investigations proved that chemical modification of the polymer occurs and the degree of the photo-degradation depends on the treating laser wavelength as well as on the number and fluence of the laser pulses. It was demonstrated by tapping mode atomic force microscopy that bovine serum albumin attaches to surface parts having higher adhesion. The dependence of the protein adherence on the surface treatment conditions was demonstrated based on the C 1s and O 1s spectra and on the proteinaceous nitrogen level.