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

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.

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

Materials ◽

10.3390/ma13010200 ◽

2020 ◽

Vol 13 (1) ◽

pp. 200 ◽

Cited By ~ 2

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.

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Rapid Fabrication of Periodic Patterns on Poly(styrene-co-acrylonitrile) Surfaces Using Direct Laser Interference Patterning

International Journal of Polymer Science ◽

10.1155/2015/721035 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7 ◽

Cited By ~ 8

Author(s):

Martin F. Broglia ◽

Diego F. Acevedo ◽

Denise Langheinrich ◽

Heidi R. Perez-Hernandez ◽

Cesar A. Barbero ◽

...

Keyword(s):

Laser Fluence ◽

Polymerization Process ◽

Periodic Pattern ◽

Copolymer Composition ◽

Laser Interference ◽

Periodic Patterns ◽

Scanning Calorimetry ◽

Direct Laser ◽

Periodic Microstructures ◽

Direct Laser Interference Patterning

Periodic microstructures in styrene-acrylonitrile (SAN) copolymers are fabricated by two-beam direct laser interference patterning using a nanosecond pulsed laser operating at a wavelength of 266 nm. The SAN copolymers are synthesized using different molar ratios (styrene to acrylonitrile) by a free radical polymerization process. The chemical composition of the copolymers and their properties are determined using Fourier transformed infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Depending on the composition of the irradiated copolymer films, with weight ratios ranging from 58 to 96.5% of styrene to acrylonitrile, different ablation behaviors are observed. The laser fluence necessary to locally ablate the copolymer is found to be dependent on the copolymer composition. Unlike other dielectric polymers, the laser irradiation produced both direct ablation of the irradiated material and collapse of the surface. It is shown that, by varying the laser fluence and the copolymer composition, the surface structure can be changed from a periodic pattern with a swelled topography to an ablated-like structure. The number of holes does not depend monotonically on the amount of PS or PAN units but shows a more complex behavior which depends on the copolymer composition and the laser fluence.

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Improving the homogeneity of diffraction based colours by fabricating periodic patterns with gradient spatial period using Direct Laser Interference Patterning

Scientific Reports ◽

10.1038/s41598-019-44212-4 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 6

Author(s):

Bogdan Voisiat ◽

Wei Wang ◽

Max Holzhey ◽

Andrés Fabián Lasagni

Keyword(s):

Spatial Period ◽

Laser Interference ◽

Periodic Patterns ◽

Direct Laser ◽

Direct Laser Interference Patterning

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

Materials ◽

10.3390/ma12203409 ◽

2019 ◽

Vol 12 (20) ◽

pp. 3409 ◽

Cited By ~ 2

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.

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High Throughput Direct Laser Interference Patterning of Aluminum for Fabrication of Super Hydrophobic Surfaces

Materials ◽

10.3390/ma12091484 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1484 ◽

Cited By ~ 3

Author(s):

Valentin Lang ◽

Bogdan Voisiat ◽

Andrés Fabián Lasagni

Keyword(s):

High Throughput ◽

Hydrophobic Surface ◽

Surface Structures ◽

Laser Interference ◽

Heat Accumulation ◽

Water Contact ◽

Laser Beam Intensity ◽

Aspect Ratios ◽

Direct Laser ◽

Direct Laser Interference Patterning

This work addresses the fabrication of hydrophobic surface structures by means of direct laser interference patterning using an optical setup optimized for high throughput processing. The developed optical assembly is used to shape the laser beam intensity as well as to obtain the two sub beams required for creating the interference pattern. The resulting beam profile consists of an elongated rectangular laser spot with 5.0 mm × 0.1 mm size, which enables the optimized utilization of the laser fluence available from an ns-pulsed laser with a wavelength of 1064 nm. Depending on the pulse repetition rate applied, heating of the substrate volume generated by heat accumulation encouraged exceptionally high aspect ratios of the trench structures due to melt flow dynamic material deformation. Finally, water contact angle measurements of the produced structures permitted the demonstration of the capability of controlling the wetting angle, in which this effect does not only depend on the height of the generated surface structures but also on their morphology.

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Hierarchical Microtextures Embossed on PET from Laser-Patterned Stamps

Materials ◽

10.3390/ma14071756 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1756

Author(s):

Felix Bouchard ◽

Marcos Soldera ◽

Robert Baumann ◽

Andrés Fabián Lasagni

Keyword(s):

High Speed ◽

Laser Scanning ◽

Contact Angles ◽

Spatial Period ◽

Water Contact ◽

Microscopy Imaging ◽

Drop Shape ◽

Direct Laser ◽

Direct Laser Interference Patterning ◽

Processing Steps

Nowadays, the demand for surface functionalized plastics is constantly rising. To address this demand with an industry compatible solution, here a strategy is developed for producing hierarchical microstructures on polyethylene terephthalate (PET) by hot embossing using a stainless steel stamp. The master was structured using three laser-based processing steps. First, a nanosecond-Direct Laser Writing (DLW) system was used to pattern dimples with a depth of up to 8 µm. Next, the surface was smoothed by a remelting process with a high-speed laser scanning at low laser fluence. In the third step, Direct Laser Interference Patterning (DLIP) was utilized using four interfering sub-beams to texture a hole-like substructure with a spatial period of 3.1 µm and a depth up to 2 µm. The produced stamp was used to imprint PET foils under controlled temperature and pressure. Optical confocal microscopy and scanning electron microscopy imaging showed that the hierarchical textures could be accurately transferred to the polymer. Finally, the wettability of the single- and multi-scaled textured PET surfaces was characterized with a drop shape analyzer, revealing that the highest water contact angles were reached for the hierarchical patterns. Particularly, this angle was increased from 77° on the untreated PET up to 105° for a hierarchical structure processed with a DLW spot distance of 60 µm and with 10 pulses for the DLIP treatment.

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Automated spatial period variation for direct laser interference patterning

Laser-based Micro- and Nanoprocessing XV ◽

10.1117/12.2579507 ◽

2021 ◽

Author(s):

Ludwig Pongratz ◽

Kai Vannahme

Keyword(s):

Period Variation ◽

Spatial Period ◽

Laser Interference ◽

Direct Laser ◽

Direct Laser Interference Patterning

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Fabrication of superhydrophobic and ice-repellent surfaces on pure aluminium using single and multiscaled periodic textures

Scientific Reports ◽

10.1038/s41598-019-49615-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 19

Author(s):

Stephan Milles ◽

Marcos Soldera ◽

Bogdan Voisiat ◽

Andrés F. Lasagni

Keyword(s):

Fold Increase ◽

Patterned Surfaces ◽

Geometrical Shape ◽

Pure Aluminium ◽

Periodic Patterns ◽

Water Contact ◽

Direct Laser ◽

Hydrophobic Nature ◽

Direct Laser Interference Patterning ◽

Substrate Temperatures

Abstract Fabricating aluminium surfaces with superhydrophobic and ice-repellent properties present nowadays a challenging task. In this work, multifunctional structures are manufactured by direct laser writing and direct laser interference patterning methods using pulsed infrared laser radiation (1064 nm). Different periodic patterns with feature sizes ranging from 7.0 to 50.0 µm are produced. In addition, hierarchical textures are produced combining both mentioned laser based methods. Water contact angle tests at room temperature showed that all produced patterns reached the superhydrophobic state after 13 to 16 days. In addition, these experiments were repeated at substrate temperatures from −30 °C to 80 °C allowing to determine three wettability behaviours as a function of the temperature. The patterned surfaces also showed ice-repellent properties characterized by a near three-fold increase in the droplets freezing times compared to the untreated samples. Using finite element simulations, it was found that the main reason behind the ice-prevention is the change in the droplet geometrical shape due to the hydrophobic nature of the treated surfaces. Finally, dynamic tests of droplets imping the treated aluminium surfaces cooled down to −20 °C revealed that only on the hierarchically patterned surface, the droplets were able to bounce off the substrate.

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A Fundamental Study of a Surface Modification on Silicon Wafer Using Direct Laser Interference Patterning with 355-nm UV Laser

Science of Advanced Materials ◽

10.1166/sam.2020.3658 ◽

2020 ◽

Vol 12 (4) ◽

pp. 516-519

Author(s):

Dong-Bin You ◽

Jun-Han Park ◽

Bo-Seok Kang ◽

Dan-Hee Yun ◽

Bo Sung Shin

Keyword(s):

Basic Research ◽

Interference Lithography ◽

Uv Laser ◽

Laser Interference ◽

Periodic Patterns ◽

Element Analysis ◽

Fundamental Study ◽

Laser Lithography ◽

Direct Laser ◽

Direct Laser Interference Patterning

The growing need for precision machining, which is difficult to achieve using conventional mechanical machining techniques, has fueled interest in laser patterning. Ultraviolet (UV) pulsed-lasers have been used in various applications, including the micro machining of polymers and metals. In this study, we investigated direct laser interference patterning of a silicon waver using a third-harmonic diode-pumped solid-state UV laser with a wavelength of 355 nm. Direct laser lithography is much more simple process compare to other submicro processing method. We have studied interference patterning for silicon wafers as a basic research for direct laser interference patterning on wafer surfaces without mask. And Finite element analysis (FEA) was performed for a 150° biprism using modeling software (COMSOL Multiphysics 5.4) to determine changes in the periodic patterns according to the focusing distance in the direct interference lithography experiment. In further study, we expect this technique to be applied to direct laser interference lithography on metals.

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