Subwavelength Direct Laser Nanopatterning Via Microparticle Arrays for Functionalizing Metallic Surfaces

Jean-Michel Romano,Haider Butt,Stefan Dimov,Antonio Garcia-Giron,Carsten Werner,Melissa Sikosana,Rajib Ahmed,Ralf Helbig,Olivier Delléa,Pavel Penchev

doi:10.1115/1.4042964

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.

Highlights

Techniques for selective micro- and nanopatterning of metallic surfaces have attracted a growing interest due to their novel optical [1,2,3], wettability [4,5,6], and antimicrobiological [7,8,9,10,11] applications
In the last 10 years, a promising nanofabrication route involving microparticles as near field focal enhancement systems was developed [15,16]. This method benefits from the near field optical phenomena, called Photonic Nanojet (PN), that allows a beam focusing beyond the optical diffraction limit of light [17,18,19]
Such techniques were often applied for particles with much larger sizes than the wavelength and the focal spot sizes were calculated to be in the range from 0.8λ down to 0.15λ depending on the refraction indexes of the particles and the propagation medium [21,38,39]

Summary

Introduction

Techniques for selective micro- and nanopatterning of metallic surfaces have attracted a growing interest due to their novel optical [1,2,3], wettability [4,5,6], and antimicrobiological [7,8,9,10,11] applications. In the last 10 years, a promising nanofabrication route involving microparticles as near field focal enhancement systems was developed [15,16]. This method benefits from the near field optical phenomena, called Photonic Nanojet (PN), that allows a beam focusing beyond the optical diffraction limit of light [17,18,19]. A preliminary step is required to apply the PN technology for surface texturing, i.e. the deposition of a microspheres’ monolayer on a substrate. Self-assembly processes such as Langmuir-Blodgett techniques can be applied for microspheres’

Methods

Results

Conclusion