The influence of KrF excimer laser irradiation on the surface of collagen and collagen/PVP films

The surface properties of collagen and collagen/poly(vinyl pyrrolidone) (PVP) films after KrF excimer laser irradiation (λ=248nm) were investigated by means of the technique of scanning electron microscopy (SEM) and optical microscopy (OM). The laser irradiation of the used specimens caused an expansion of materials above their surface with pronounced sings of its melting. The height of the ablated volume in a case of collagen film at a fluence of 1.1J/cm2 was approximately 5μm. A white damage appears on the treated surfaces at a threshold of 0.5J/cm2 with a single pulse and becomes more visible for a higher fluence. It is also noteworthy that along with increasing fluences (beginning from the fluence of 1.7J/cm2), the characteristic filaments at the spot edges are observed. The local heat and pressure generated by the laser radiation were able to induce bubble formation on the surface. Further bubble colliding and bursting produce a three-dimensional polymer “microfoam” structure with interconnected pores. These results can be of interest for some new applications.