Functionalized metallic nanofeatures can be selectively fabricated via ultrashort laser processing; however, the cost-effective large-area texturing, intrinsically constrained by the diffraction limit of light, remains a challenging issue. A high-intensity near-field phenomenon that takes place when irradiating microsized spheres, referred to as photonic nanojet (PN), was investigated in the transitional state between geometrical optics and dipole regime to fabricate functionalized metallic subwavelength features. Finite element simulations were performed to predict the PN focal length and beam spot size, and nanofeature formation. A systematic approach was employed to functionalize metallic surface by varying the pulse energy, focal offset, and number of pulses to fabricate controlled array of nanoholes and to study the generation of triangular and rhombic laser-induced periodic surface structures (LIPSS). Finally, large-area texturing was investigated to minimize the dry laser cleaning (DLC) effect and improve homogeneity of PN-assisted texturing. Tailored dimensions and densities of achievable surface patterns could provide hexagonal light scattering and selective optical reflectance for a specific light wavelength. Surfaces exhibited controlled wetting properties with either hydrophilicity or hydrophobicity. No correlation was found between wetting and microbacterial colonization properties of textured metallic surfaces after 4 h incubation of Escherichia coli. However, an unexpected bacterial repellency was observed.
Bibliographical noteFunding Information:
• H2020 European Research Council (Grant No. 766871; Funder ID: 10.13039/100010663).
• H2020 Marie Sklodowska-Curie Actions (Grant No. 675063; Funder ID: 10.13039/100010665).
This work was carried out within the framework of the H2020 ITN program “European ESRs network on short pulsed laser micro/nanostructuring of surfaces for improved functional applications” under the Marie Skłodowska-Curie grant agreement No. 675063.2 In addition, the work was supported by two other H2020 FoF programs, i.e., the projects on “Modular laser-based additive manufacturing platform for large-scale industrial applications” (MAESTRO) and “High-Impact Injection Moulding Platform for mass-production of 3D and/or large microstructured surfaces with Antimicrobial, Self-cleaning, Anti-scratch, Anti-squeak, and Aesthetic functionalities” (HIMALAIA).
© 2019 ASME.
- hexagonal closepacked monolayer
- photonic nanojet
- laser ablation
- sub-micron patterning
ASJC Scopus subject areas
- Mechanics of Materials
- Process Chemistry and Technology
- Industrial and Manufacturing Engineering