scholarly journals Development of an Analytical Model for Optimization of Direct Laser Interference Patterning

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 200 ◽  
Author(s):  
Bogdan Voisiat ◽  
Alfredo I. Aguilar-Morales ◽  
Tim Kunze ◽  
Andrés Fabián Lasagni
Keyword(s):  
Analytical Model ◽  
Periodic Structures ◽  
Processing Parameters ◽  
Morphological Properties ◽  
Laser Source ◽  
Spatial Period ◽  
Laser Interference ◽  
Large Area ◽  
Direct Laser ◽  
Direct Laser Interference Patterning

Direct laser interference patterning (DLIP) has proven to be a fast and, at the same time, high-resolution process for the fabrication of large-area surface structures. In order to provide structures with adequate quality and defined morphology at the fastest possible fabrication speed, the processing parameters have to be carefully selected. In this work, an analytical model was developed and verified by experimental data, which allows calculating the morphological properties of periodic structures as a function of most relevant laser-processing parameters. The developed model permits to improve the process throughput by optimizing the laser spot diameter, as well as pulse energy, and repetition rate. The model was developed for the structures formed by a single scan of the beam in one direction. To validate the model, microstructures with a 5.5 µm spatial period were fabricated on stainless steel by means of picosecond DLIP (10 ps), using a laser source operating at a 1064 nm wavelength. The results showed a difference of only 10% compared to the experimental results.

scholarly journals Direct Laser Interference Patterning of Diffraction Gratings in Safrofilcon-A Hydrogel: Fabrication and Hydration Assessment

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 679
Author(s):  
Daniel Sola ◽  
Stephan Milles ◽  
Andrés F. Lasagni
Keyword(s):  
Laser Fluence ◽  
Contact Lenses ◽  
Laser Source ◽  
Spatial Period ◽  
Laser Interference ◽  
Periodic Patterns ◽  
Hydration Properties ◽  
Water Contact ◽  
Direct Laser ◽  
Direct Laser Interference Patterning

Refractive index modification by laser micro-structuration of diffractive optical devices in ophthalmic polymers has recently been applied for refractive correction in the fields of optics and ophthalmology. In this work, Safrofilcon-A hydrogel, used as soft contact lenses, was processed by direct laser interference patterning (DLIP) to fabricate linear periodic patterns on the surface of the samples. Periodic modulation of the surface was attained under two-beam interference by using a Q-switched laser source with emission at 263 nm and 4 ns pulse duration. Features of processed areas were studied as a function of both the interference spatial period and the laser fluence. Optical confocal microscopy used to evaluate the topography of the processed samples showed that both structured height and surface roughness increased with laser fluence. Static water contact angle (WCA) measurements were carried out with deionized water droplets on the structured areas to evaluate the hydration properties of DLIP structures. It was observed that the laser structured areas induced a delay in the hydration process. Finally, microstructural changes induced in the structured areas were assessed by confocal micro-Raman spectroscopy showing that at low laser fluences the polymer structure remained almost unaltered. In addition, Raman spectra of hydrated samples recovered the original shape of areas structured at low laser fluence.

scholarly journals Picosecond Laser Interference Patterning of Periodical Micro-Architectures on Metallic Molds for Hot Embossing

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3409 ◽  
Author(s):  
Yangxi Fu ◽  
Marcos Soldera ◽  
Wei Wang ◽  
Bogdan Voisiat ◽  
Andrés Fabián Lasagni
Keyword(s):  
Picosecond Laser ◽  
Processing Parameters ◽  
Hot Embossing ◽  
Surface Structures ◽  
Laser Source ◽  
Laser Interference ◽  
Periodic Surface ◽  
Direct Laser ◽  
Direct Laser Interference Patterning ◽  
532 Nm

In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.

Design of Perfectly Ordered Periodic Structures on Polymers Using Direct Laser Interference Patterning

2019 ◽  
pp. 157-180
Author(s):  
Andrés Fabián Lasagni ◽  
Sabri Alamri ◽  
Florian Rößler ◽  
Valentin Lang ◽  
Bogdan Voisiat
Keyword(s):  
Periodic Structures ◽  
Laser Interference ◽  
Direct Laser ◽  
Direct Laser Interference Patterning

scholarly journals Simultaneous Micro-Structuring and Surface Smoothing of Additive Manufactured Parts Using DLIP Technique and Its Influence on the Wetting Behaviour

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2563
Author(s):  
Florian Kuisat ◽  
Fabian Ränke ◽  
Fernando Lasagni ◽  
Andrés Fabián Lasagni
Keyword(s):  
Near Infrared ◽  
Mechanical Performance ◽  
Periodic Structures ◽  
Morphological Characteristics ◽  
Laser Source ◽  
Angle Measurements ◽  
Direct Laser ◽  
Contact Angle Measurements ◽  
Micro Structuring ◽  
Direct Laser Interference Patterning

It is well known that the surface topography of a part can affect its function as well as its mechanical performance. In this context, we report on the surface modification of additive manufactured components made of Titanium 64 and Scalmalloy®, using Direct Laser Interference Patterning technique. In our experiments, a nanosecond-pulsed near-infrared laser source with a pulse duration of 10 ns was used. By varying the process parameters, periodic structures with different depths and associated roughness values are produced. Additionally, the influence of the resultant morphological characteristics on the wettability behaviour of the fabricated textures is investigated by means of contact angle measurements. The results demonstrated a reduction of the surface roughness of the additive manufactured parts (in the order of some tens of micrometres) and simultaneously the production of well-defined micro-patterns (in the micrometre range), which allow the wettability of the surfaces from 26° and 16° up to 93° and 131° to be tuned for Titanium 6Al 4V and Al-Mg-Sc (Scalmalloy®), respectively.

scholarly journals Detection and analysis of photo-acoustic emission in Direct Laser Interference Patterning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tobias Steege ◽  
Sabri Alamri ◽  
Andrés Fabián Lasagni ◽  
Tim Kunze
Keyword(s):  
Acoustic Emission ◽  
Processing Parameters ◽  
Direct Result ◽  
Laser Interference ◽  
Lotus Effect ◽  
Spectral Signatures ◽  
Direct Laser ◽  
3D Processing ◽  
Direct Laser Interference Patterning

AbstractFunctional laser texturing by means of Direct Laser Interference Patterning is one of the most efficient approaches to fabricate well-defined micro textures which mimic natural surfaces, such as the lotus effect for self-cleaning properties or shark skin for reduced friction. While numerous technical and theoretical improvements have been demonstrated, strategies for process monitoring are yet to be implemented in DLIP, for instance aiming to treat complex and non-plane surfaces. Over the last 35 years, it has been shown that the sound pressure generated by a laser beam hitting a surface and producing ablation can be detected and analysed using simple and commercially available transducers and microphones. This work describes the detection and analysis of photo-acoustic signals acquired from airborne acoustic emission during DLIP as a direct result of the laser–material interaction. The study includes the characterization of the acoustic emission during the fabrication of line-like micro textures with different spatial periods and depths, the interpretation the spectral signatures deriving from single spot and interference ablation, as well as a detailed investigation of the vertical extent of the interference effect based on the ablated area and its variation with the interference period. The results show the possibility to develop an autofocusing system using only the signals from the acoustic emission for 3D processing, as well as the possibility to predict deviations in the DLIP processing parameters.

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