The exciting properties of micro-and nano-patterned surfaces found in natural species hide a virtually endless potential of technological ideas, opening new opportunities for innovation and exploitation in materials science and engineering. Due to the diversity of biomimetic surface functionalities, inspirations from natural surfaces are interesting for a broad range of applications in engineering, including phenomena of adhesion, friction, wear, lubrication, wetting phenomena, self-cleaning, antifouling, antibacterial phenomena, thermoregulation and optics. Lasers are increasingly proving to be promising tools for the precise and controlled structuring of materials at micro-and nano-scales. When ultrashort-pulsed lasers are used, the optimal interplay between laser and material parameters enables structuring down to the nanometer scale. Besides this, a unique aspect of laser processing technology is the possibility for material modifications at multiple (hierarchical) length scales, leading to the complex biomimetic micro-and nano-scale patterns, while adding a new dimension to structure optimization. This article reviews the current state of the art of laser processing methodologies, which are being used for the fabrication of bioinspired artificial surfaces to realize extraordinary wetting, optical, mechanical, and biological-active properties for numerous applications. The innovative aspect of laser functionalized biomimetic surfaces for a wide variety of current and future applications is particularly demonstrated and discussed. The article concludes with illustrating the wealth of arising possibilities and the number of new laser micro/nano fabrication approaches for obtaining complex high-resolution features, which prescribe a future where control of structures and subsequent functionalities are beyond our current imagination.

Laser-induced periodic surface structures (LIPSS) are a universal phenomenon observed in all classes of solid materials, giving rise to a variety of self-assembled subwavelength structures with different symmetries. These promising features have opened new opportunities for laser structuring of materials in a wide range of applications, including plasmonics, nanophotonics, nanoelectronics, sensing and even mechanics. However, there is an ongoing debate about the formation mechanism of LIPSS and the current picture stems mainly from the combined effort of theoretical modeling and experimental studies of the final structures produced. Here we demonstrate femtosecondresolved imaging of the formation process of such structures produced by ultrashort laser pulses in silicon. The particular type of LIPSS studied are well-aligned amorphouscrystalline fringes generated in dynamic processing conditions, whose period can be tuned and which can be extended over large areas. Using a moving-spot, multiple-pulse irradiation approach we are able to spatially and temporally resolve the birth and growth of individual fringes. We demonstrate that the formation process is initiated by free electron generation leading to non-thermal melting, liquid phase overheating and rapid solidification into the amorphous phase.

The formation of self-organized laser induced periodic surface structures (LIPSS) in metals, semiconductors and dielectrics upon pulsed laser irradiation is a well-known phenomenon, receiving increased attention due to its huge technological potential. For the case of metals, a major role in this process is played by surface plasmon polaritons (SPPs) propagating at the interface of the metal with the medium of incidence. Yet, simple and advanced models based on SPP propagation sometimes fail to explain experimental results, even of basic features as the LIPSS period. We experimentally demonstrate, for the particular case of LIPSS on Cu, that significant deviations of the structure period from the predictions of the standard model are observed, which are very pronounced for elevated angles of laser incidence. In order to explain this deviation, we introduce a model based on the propagation of a SPP on a rough surface that takes into account the influence of the specific roughness properties on the SPP wave vector. Good agreement of the modelling results with the experimental data is observed, which highlights the potential of this model for the general understanding of LIPSS in other metals.