Automated spatial period variation for direct laser interference patterning

2021 ◽  
Author(s):  
Ludwig Pongratz ◽  
Kai Vannahme
Keyword(s):  
Period Variation ◽  
Spatial Period ◽  
Laser Interference ◽  
Direct Laser ◽  
Direct Laser Interference Patterning

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 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.

In-Depth Investigation of Copper Surface Chemistry Modification by Ultrashort Pulsed Direct Laser Interference Patterning

Langmuir ◽  
2020 ◽  
Vol 36 (45) ◽  
pp. 13415-13425 ◽  
Author(s):  
Daniel W. Müller ◽  
Anne Holtsch ◽  
Sarah Lößlein ◽  
Christoph Pauly ◽  
Christian Spengler ◽  
...  
Keyword(s):  
Surface Chemistry ◽  
Copper Surface ◽  
Laser Interference ◽  
Direct Laser ◽  
Surface Chemistry Modification ◽  
Direct Laser Interference Patterning

scholarly journals Wettability control of polymeric microstructures replicated from laser-patterned stamps

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yangxi Fu ◽  
Marcos Soldera ◽  
Wei Wang ◽  
Stephan Milles ◽  
Kangfa Deng ◽  
...  
Keyword(s):  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Spatial Period ◽  
Structured Surfaces ◽  
High Adhesion ◽  
Direct Laser ◽  
Periodic Microstructures ◽  
Structure Height ◽  
Direct Laser Interference Patterning ◽  
Micropillar Arrays

AbstractIn this study, two-step approaches to fabricate periodic microstructures on polyethylene terephthalate (PET) and poly(methyl methacrylate) (PMMA) substrates are presented to control the wettability of polymeric surfaces. Micropillar arrays with periods between 1.6 and 4.6 µm are patterned by plate-to-plate hot embossing using chromium stamps structured by four-beam Direct Laser Interference Patterning (DLIP). By varying the laser parameters, the shape, spatial period, and structure height of the laser-induced topography on Cr stamps are controlled. After that, the wettability properties, namely the static, advancing/receding contact angles (CAs), and contact angle hysteresis were characterized on the patterned PET and PMMA surfaces. The results indicate that the micropillar arrays induced a hydrophobic state in both polymers with CAs up to 140° in the case of PET, without modifying the surface chemistry. However, the structured surfaces show high adhesion to water, as the droplets stick to the surfaces and do not roll down even upon turning the substrates upside down. To investigate the wetting state on the structured polymers, theoretical CAs predicted by Wenzel and Cassie-Baxter models for selected structured samples with different topographical characteristics are also calculated and compared with the experimental data.

scholarly journals Improving Throughput and Microstructure Uniformity in Direct Laser Interference Patterning Utilizing Top-Hat Shaped Beams

2021 ◽  
Author(s):  
Mikhael El-Khoury ◽  
Bogdan Voisiat ◽  
Tim Kunze ◽  
Andrés Fabián Lasagni
Keyword(s):  
Intensity Distribution ◽  
Laser Interference ◽  
Gaussian Laser Beam ◽  
Laser Beam Intensity ◽  
Direct Laser ◽  
Standard Configuration ◽  
Laser Sources ◽  
Periodic Microstructures ◽  
Direct Laser Interference Patterning ◽  
The Impact

Abstract Uniform periodic microstructures formation over large areas is generally challenging in Direct Laser Interference Patterning (DLIP) due to the Gaussian laser beam intensity distribution inherent to most commercial laser sources. In this work, a diffractive fundamental beam-mode shaper (FBS) element is implemented in a four-beam DLIP optical setup to generate a square-shaped top-hat intensity distribution in the interference volume. The interference patterns produced by a standard configuration and the developed setup are measured and compared. In particular, the impact of both laser intensity distributions on process throughput as well as fill-factor is investigated by measuring the resulting microstructure height with height error over the structured surface. It is demonstrated that by utilizing top-hat-shaped interference patterns, it is possible to produce on average 44.8 % deeper structures with up to 60 % higher homogeneity at the same throughput. Moreover, the presented approach allows the production of microstructures with comparable height and homogeneity compared to the Gaussian intensity distribution with increased throughput of 53%.

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