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- Femtosecond laser (6)
- Laser-induced periodic surface structures (LIPSS) (5)
- Femtosecond laser ablation (3)
- Laser ablation (3)
- Laser-induced periodic surface structures (3)
- Steel (3)
- Fluid transport (2)
- Nanostructures (2)
- Surface functionalization (2)
- Surface wetting (2)
- Anodic oxidation (1)
- Application (1)
- Auger electron spectroscopy (1)
- Biofilms (1)
- Biomometics (1)
- Bug (1)
- CIGSe (1)
- CIGSe micro solar cells (1)
- Cell adhesion (1)
- Copper-indium-gallium-diselenide (1)
- Darkfield microscopy (1)
- Dielectrics (1)
- Diffusion (1)
- Electromagnetic scattering (1)
- Femtosecond laser patterning (1)
- Friction (1)
- Indium islands (1)
- Laser Processing (1)
- Laser processing (1)
- Laser-induced forward transfer (LIFT) (1)
- Laser-induced periodic surface structures, LIPSS (1)
- Lizard (1)
- Micro-concentrator solar cell (1)
- Microbial adhesion tests (1)
- Oxidation (1)
- Pacemaker (1)
- Raman spectroscopy (1)
- Refractive index (1)
- Scattering (1)
- Silicate glasses (1)
- Structural relaxation (1)
- Surface plasmon polariton (1)
- Surface texture (1)
- Titanium (1)
- Titanium alloy (1)
- Titanium nitride films (1)
- Ultrafast microscopy (1)
- Wear (1)
Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon that can be observed on almost any material after the irradiation by linearly polarized laser beams, particularly when using ultrashort laser pulses with durations in the picosecond to femtosecond range. During the past few years significantly increasing research activities have been reported in the field of LIPSS, since their generation in a single-step process provides a simple way of nanostructuring and surface functionalization towards the control of optical, mechanical or chemical properties. In this contribution current applications of LIPSS are reviewed, including the colorization of technical surfaces, the control of surface wetting, the tailoring of surface colonization by bacterial biofilms, and the improvement of the tribological performance of nanostructured metal surfaces.
In order to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS) on single-crystalline zinc oxide (ZnO), two-colour double-fs-pulse experiments were performed. Parallel or cross-polarised double-pulse sequences at 400 and 800 nm wavelength were generated by a Mach–Zehnder interferometer, exhibiting inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Twenty two-colour double-pulse sequences were collinearly focused by a spherical mirror to the sample surface. The resulting LIPSS periods and areas were analysed by scanning electron microscopy. The delay-dependence of these LIPSS characteristics shows a dissimilar behaviour when compared to the semiconductor silicon, the dielectric fused silica, or the metal titanium. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS on ZnO when considering multi-photon excitation processes. Our results support the involvement of nonlinear processes for temporally overlapping pulses. These experiments extend previous two-colour studies on the indirect semiconductor silicon towards the direct wide band-gap semiconductor ZnO and further manifest the relevance of the ultrafast energy deposition for LIPSS formation.
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon and can be generated on almost any material upon irradiation with linearly polarized radiation. With the availability of ultrashort laser pulses, LIPSS have gained an increasing attraction during the past decade, since these structures can be generated in a simple single-step process, which allows a surface nanostructuring for tailoring optical, mechanical, and chemical surface properties. In this study, the current state in the field of LIPSS is reviewed. Their formation mechanisms are analyzed in ultrafast time-resolved scattering, diffraction, and polarization constrained double-pulse experiments. These experiments allow us to address the question whether the LIPSS are seeded via ultrafast energy deposition mechanisms acting during the absorption of optical radiation or via self-organization after the irradiation process. Relevant control parameters of LIPSS are identified, and technological applications featuring surface functionalization in the fields of optics, fluidics, medicine, and tribology are discussed.