Abstract
Femtosecond laser induced changes on the topography of stainless steel with double pulses is investigated to reveal the role of parameters such as the fluence, the energy dose and the interpulse delay on the features of the produced patterns. Our results indicate that short pulse separation (Δτ = 5 ps) favors the formation of 2D Low Spatially Frequency Laser Induced Periodic Surface Structures (LSFL) while longer interpulse delays (Δτ = 20 ps) lead to 2D High Spatially Frequency LIPSS (HSFL). The detailed investigation is complemented with an analysis of the produced surface patterns and characterization of their wetting and cell-adhesion properties. A correlation between the surface roughness and the contact angle is presented which confirms that topographies of variable roughness and complexity exhibit different wetting properties. Furthermore, our analysis indicates that patterns with different spatial characteristics demonstrate variable cell adhesion response which suggests that the methodology can be used as a strategy towards the fabrication of tailored surfaces for the development of functional implants.
Highlights
Over the past decades, laser patterning of various materials with ultrashort pulses is of particular importance due to its applicability in a vast number of areas in science, technology and industry [1,2,3,4,5,6]
Based on the results of parametric studies presented in previous reports [18,33], in this work, two different interpulse delay (∆τ) values in the picosecond regime were chosen to be investigated thoroughly in order to generate structures with various spatial characteristics; ∆τ = 5 ps to study the hierarchical 2D morphology consisting of High Spatially Frequency Laser InducedPeriodic Surface Structures (LIPSS) (HSFL) and LSFL [18] and ∆τ = 20 ps to explore the 2D-HSFL formation [26]
A general conclusion from the above results is that structures with different spatial characteristics can exhibit variable cell adhesion properties
Summary
Laser patterning of various materials with ultrashort pulses is of particular importance due to its applicability in a vast number of areas in science, technology and industry [1,2,3,4,5,6]. The capability to produce an abundance of complex bioinspired surfaces exhibiting hierarchical structuring at length scales ranging from hundreds of nanometers to several micrometers unveils the advantage of the employment of laser technology. Numerous examples of functional surfaces have been reported on biological systems and reproduced through laser techniques. The fabrication of surfaces with impressive superhydrophobic [3], antifouling [7], antireflective [8], antibacterial [9], drag reduction [10] and other properties have been reported (see [1] and references therein). One dominant laser-based methodology to produce such surface patterns is through a self-organization fashion, and the fabrication of the Laser Induced. Tailoring of the produced topographies can be achieved through varying a range of laser parameters such as the fluence, energy dose, polarization, laser wavelength, incident angle, pulse duration
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