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

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
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.

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 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%.

scholarly journals An Incompressible Smoothed Particle Hydrodynamics (ISPH) Model of Direct Laser Interference Patterning

Computation ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Cornelius Demuth ◽  
Andrés Fabián Lasagni
Keyword(s):  
Stainless Steel ◽  
Smoothed Particle Hydrodynamics ◽  
Shear Stresses ◽  
Laser Interference ◽  
Melt Pool ◽  
Direct Laser ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Periodic Microstructures ◽  
Direct Laser Interference Patterning

Functional surfaces characterised by periodic microstructures are sought in numerous technological applications. Direct laser interference patterning (DLIP) is a technique that allows the fabrication of microscopic periodic features on different materials, e.g., metals. The mechanisms effective during nanosecond pulsed DLIP of metal surfaces are not yet fully understood. In the present investigation, the heat transfer and fluid flow occurring in the metal substrate during the DLIP process are simulated using a smoothed particle hydrodynamics (SPH) methodology. The melt pool convection, driven by surface tension gradients constituting shear stresses according to the Marangoni boundary condition, is solved by an incompressible SPH (ISPH) method. The DLIP simulations reveal a distinct behaviour of the considered substrate materials stainless steel and high-purity aluminium. In particular, the aluminium substrate exhibits a considerably deeper melt pool and remarkable velocity magnitudes of the thermocapillary flow during the patterning process. On the other hand, convection is less pronounced in the processing of stainless steel, whereas the surface temperature is consistently higher. Marangoni convection is therefore a conceivable effective mechanism in the structuring of aluminium at moderate fluences. The different character of the melt pool flow during DLIP of stainless steel and aluminium is confirmed by experimental observations.

Direct Fabrication of Hierarchical Microstructures on Metals by Means of Direct Laser Interference Patterning

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Matthias Bieda ◽  
Eckhard Beyer ◽  
Andrés F. Lasagni
Keyword(s):  
Thermal Effects ◽  
Laser Interference ◽  
Metallic Substrates ◽  
Vaporization Temperature ◽  
Direct Fabrication ◽  
Direct Laser ◽  
Periodic Microstructures ◽  
Thermal Simulations ◽  
Direct Laser Interference Patterning

We have studied the fabrication of hierarchical periodic microstructures on metals by means of direct laser interference patterning. A nanosecond pulsed Nd:YAG laser at 355 nm wavelength was used to produce the microstructures with grating periods ranging from 1 μm to 10 μm on stainless steel, titanium, and aluminum. The results indicate that the geometrical characteristics of the interference patterns as well as the thermal properties of the substrates determine the quality of the fabricated structures. In particular, the best structures were obtained when the material at the interference minima position remained in the solid state and the temperature at the interference maxima is below the vaporization temperature. Thermal simulations by finite element method were carried out modeling photothermal interactions of the interference pattern with the metallic substrates to evaluate laser induced thermal effects, such as temperature distribution and temperature gradients and, thus, enabling us to explain the obtained results.

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

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.

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.

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