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the desired machining process is complete. In contrast, LIPSS can be fabricated on
virtually any material when irradiated with linearly polarised high-intensity ultrashort laser pulses, typically under loosely focused conditions – large beam spots. The morphology of LIPSS corresponds to period lines arranged in parallel, featuring periods that can be controlled to between approximately 100nm and a few micrometres. Their orientation is strongly influenced by the polarisation of the laser beam used. It means that it is possible, for example, to produce nanometric-spaced lines perpendicular to the laser polarisation, with a laser beam size at the irradiated surface 1,000 times bigger than their periodicity. This enables larger areas to be covered with nanostructures faster than conventional laser-direct writing. In an additive approach, these surface nanostructures can be easily superimposed to other surface microstructures, resulting in hybrid surface structures with multiscale surface roughnesses. Through all these surface topographies, along with accompanying laser-induced chemical alterations at the surface, different surface functionalisations can be realised, ranging from structural colourisation or antireflective properties (as seen on certain butterflies), over a control of surface hydrophilicity/-phobicity (as is the case
on lotus leaves), and toward unidirectional liquid transport (as realised by moisture- harvesting lizards or bark bugs). The current advancements in fast laser
scanning heads, combined with high- repetition rate femtosecond lasers, will enable LIPSS to be produced at industrially relevant scales and speeds, which in the end will translate to cheaper fabrication costs and higher production rates. The fabrication
“In an additive approach, these surface
nanostructures can be superimposed to other surface microstructures”
process is compatible and reproducible at room temperature and in an air atmosphere; very attractive to most industries that work under similar conditions.
Your research team has been investigating mechanisms in the formation of LIPSS to better understand how and when those structures can be formed; what are some of the applications? Our research group is specialised in developing strategies based on lasers to understand the mechanisms of interaction
between ultrashort laser pulses and matter, to micro- and nanofabricate materials for specific applications. Last year, we successfully finished a
three-year international research project, LiNaBioFluid, funded by the European Commission. One of the goals was to produce LIPSS on industrially-relevant materials and scales to decrease the friction coefficient in tribological applications. We also developed strategies based on LIPSS for passive fluid transport applications, including commercial lubricants, all based on biomimicking structures in nature. As a continuation of this project, we
are working in another European project called CellFreeImplant, which uses LIPSS to avoid unwanted cell growth on medical devices, such as smart medical implants. The promising results are in the hands of our medical project partners, with close collaboration ongoing with a large pacemaker manufacturer to potentially take this laser-based approach for so-called ‘leadless’ pacemakers to real patients. l
Interested in this research?
Join us for the Laser Nanomaterials Processing Conference at ICALEO 2019 on 7-10 October in Orlando, Florida, where Florian-Baron will present his team’s peer-reviewed paper Applications on Surface Functionalization by Laser-Induced Periodic Surface Structures (LIPSS).
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