Subwavelength Direct Laser Nanopatterning Via Microparticle Arrays for Functionalizing Metallic Surfaces

Abstract

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.

Bioadhesion in the oral cavity and approaches for biofilm management by surface modifications

“…However, on simple surface structures, strong interactions between bacteria and substrate as well as clear adhesion patterns in the initial colonization phase could be observed if the structural dimensions (size and spacing) were in the cell size range [228,230,231,[235][236][237][238][239][240]. In contrast, for structure sizes slightly below the bacterial cell size (submicron scale), inhibition of the initial microbial adhesion could be observed [229,241,242]. For much smaller nanostructures, the reported effects differ strongly between being high and low adhesive [243,244].…”

Springtail-Inspired Triangular Laser-Induced Surface Textures on Metals Using MHz Ultrashort Pulses

“…Using 1032 nm ultra short laser pulses, the comb-aligned triangles were two times larger than the springtail (see Section 3.1). Reducing the laser wavelength [4] or preliminary surface texturing [15] may generate smaller spatial LSFL periodicities that are closer to the springtail dimensions. Smaller dimensions are foreseen to lead to lower initial bioadhesion [16], for instance.…”

Enhanced Microsphere-Assisted Picosecond Laser Processing for Nanohole Fabrication on Silicon via Thin Gold Coating

“…Since each microsphere acts as a micro-lens, thus it can focus light into nanometer scale. Moreover, the contact region between the microspheres and the substrate has a near-field enhancement effect, which facilitates laser to remove material [17][18][19][20]. Therefore, microsphere-assisted laser processing has been widely used to fabricate nanohole arrays on various substrates.…”