Laser-induced periodic surface structures (LIPSS) on polymer surfaces

Frequently observed structures in laser-surface processing are ripples, also denoted as laser-induced periodic surface structures (LIPSS). Ripples originate from the interference of the incident/refracted laser light with the scattered or diffracted light near the surface. For many polymer surfaces, organized nano-ripple structures surfaces can be induced by irradiation with pulsed UV lasers with pulse lengths in the order of some nanoseconds at fluences well below the ablation threshold and with a large number of laser pulses N. After exposure to linearly polarized radiation at normal incidence, the lateral period of the observed LIPSS is close to the wavelength λ. This type of structures is usually called low spatial frequency LIPSS (LSFL). For femto-second laser light, ripples at polymer surfaces are also observed at a laser fluence above the ablation threshold, even with low numbers of laser pulses N. Under special conditions, another type of ripples with periods as small as λ/3 has been reported. This type of ripples is called high spatial frequency LIPSS (HSFL). We summarize here our work on LIPSS generation at polymers and describe potential applications in the field of self-organized formation of gold nano-wires and nano-structure induced alignment of biological cells cultivated on polymer substrates.