scholarly journals Large-Beam Picosecond Interference Patterning of Metallic Substrates

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4676
Author(s):  
Petr Hauschwitz ◽  
Dominika Jochcová ◽  
Radhakrishnan Jagdheesh ◽  
Martin Cimrman ◽  
Jan Brajer ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Laser System ◽  
Hierarchical Structures ◽  
High Energy ◽  
Contact Angles ◽  
Surface Structures ◽  
Laser Source ◽  
Metallic Substrates ◽  
And Tungsten

In this paper, we introduce a method to efficiently use a high-energy pulsed 1.7 ps HiLASE Perla laser system for two beam interference patterning. The newly developed method of large-beam interference patterning permits the production of micro and sub-micron sized features on a treated surface with increased processing throughputs by enlarging the interference area. The limits for beam enlarging are explained and calculated for the used laser source. The formation of a variety of surface micro and nanostructures and their combinations are reported on stainless steel, invar, and tungsten with the maximum fabrication speed of 206 cm2/min. The wettability of selected hierarchical structures combining interference patterns with 2.6 µm periodicity and the nanoscale surface structures on top were analyzed showing superhydrophobic behavior with contact angles of 164°, 156°, and 150° in the case of stainless steel, invar, and tungsten, respectively.

Fabrication and Wettability Analysis of Hydrophobic Stainless Steel Surfaces With Microscale Structures From Nanosecond Laser Machining

2018 ◽  
Vol 6 (3) ◽  
Author(s):  
Cong Cui ◽  
Xili Duan ◽  
Brandon Collier ◽  
Kristin M. Poduska
Keyword(s):  
Stainless Steel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Surface Structures ◽  
Laser Machining ◽  
Nanosecond Laser ◽  
Static Contact ◽  
Submicron Structures ◽  
Steel Surfaces ◽  
Hierarchical Multiscale

In this work, nanosecond laser machining is used to fabricate hydrophobic 17-4 PH stainless steel surfaces with microscale and submicron structures. Four surface structures were designed, with microscale channels and pillars (100 μm pitch size) of uniform heights (100 μm) or alternating heights (between 100 μm and 50 μm). During fabrication, the high-power laser beams also created submicron features on top of the microscale ones, leading to hierarchical, multiscale surface structures. Detailed wettability analysis was conducted on the fabricated samples. Measured static contact angles of water on these surfaces are over 130 deg without any coating, compared to ∼70 deg on the original steel surface before laser machining. Slightly lower contact angle hysteresis was also observed on the laser machined surfaces. Overall, these results agree with a simple Cassie–Baxter model for wetting that assumes only fractional surface area contact between the droplet and the surface. This work demonstrates that steel surfaces machined with relatively inexpensive nanosecond laser can achieve excellent hydrophobicity even with simple microstructural designs.

scholarly journals Micromachining of Invar with 784 Beams Using 1.3 ps Laser Source at 515 nm

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2962 ◽  
Author(s):  
Petr Hauschwitz ◽  
Bohumil Stoklasa ◽  
Jiří Kuchařík ◽  
Hana Turčičová ◽  
Michael Písařík ◽  
...  
Keyword(s):  
Coefficient Of Thermal Expansion ◽  
Light Emitting Diode ◽  
Laser System ◽  
Ultrashort Pulses ◽  
High Energy ◽  
Laser Source ◽  
Organic Light Emitting Diode ◽  
Energy Pulse ◽  
Cost Efficient ◽  
Monitoring Module

To fulfil the requirements for high-resolution organic light-emitting diode (OLED) displays, precise and high-quality micrometer-scale patterns have to be fabricated inside metal shadow masks. Invar has been selected for this application due to its unique properties, especially a low coefficient of thermal expansion. In this study, a novel cost-efficient method of multi-beam micromachining of invar will be introduced. The combination of a Meopta beam splitting, focusing and monitoring module with a galvanometer scanner and HiLASE high-energy pulse laser system emitting ultrashort pulses at 515 nm allows drilling and cutting of invar foil with 784 beams at once with high precision and almost no thermal effects and heat-affected zone, thus significantly improving the throughput and efficiency.

scholarly journals On the Interplay of DLIP and LIPSS Upon Ultra-Short Laser Pulse Irradiation

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1018 ◽  
Author(s):  
Sabri Alamri ◽  
Fotis Fraggelakis ◽  
Tim Kunze ◽  
Benjamin Krupop ◽  
Girolamo Mincuzzi ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Surface Morphology ◽  
Spot Size ◽  
Surface Structures ◽  
Laser Source ◽  
Periodic Patterns ◽  
Simultaneous Generation ◽  
Periodic Surface ◽  
Direct Laser ◽  
Surface Patterns

Controlling laser induced surface morphology is essential for developing specialized functional surfaces. This work presents novel, multi-scale periodic patterns with two-dimensional symmetry generated on stainless steel, polyimide and sapphire. The microstructures were realized by combining Direct Laser Interference Patterning with the generation of Laser Induced Periodic Surface Structures in a one-step process. An industrial, fiber femtosecond laser source emitting at 1030 nm with a pulse duration of 500 fs was utilized for the experiments. In the case of stainless steel, it was possible to create line-like or pillar-like surface patterns by rotating the polarization orientation with respect to the interference pattern. In the case of polyimide and sapphire, the absorption of the laser radiation was promoted by a multiphoton mechanism. In polyimide, grooves and pillars of several microns in depth were produced over an area much larger than the spot size. Finally, for sapphire, the simultaneous generation of interference-like pattern and laser induced periodic surface structures was realized. The results reported here provide valuable data on the feasibility to combine two state-of-the-art techniques with an industrial apparatus, to control the induced surface morphology.

scholarly journals Effect of Structure Hierarchy for Superhydrophobic Polymer Surfaces Studied by Droplet Evaporation

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 831 ◽  
Author(s):  
Nastasia Okulova ◽  
Peter Johansen ◽  
Lars Christensen ◽  
Rafael Taboryski
Keyword(s):  
Hierarchical Structures ◽  
Droplet Evaporation ◽  
Contact Angles ◽  
Surface Structures ◽  
Water Contact ◽  
Surface Design ◽  
Force Microscopy ◽  
Extrusion Coating ◽  
Coating Method ◽  
Micro Pillars

Super-hydrophobic natural surfaces usually have multiple levels of structure hierarchy. Here, we report on the effect of surface structure hierarchy for droplet evaporation. The two-level hierarchical structures studied comprise micro-pillars superimposed with nanograss. The surface design is fully scalable as structures used in this study are replicated in polypropylene by a fast roll-to-roll extrusion coating method, which allows effective thermoforming of the surface structures on flexible substrates. As one of the main results, we show that the hierarchical structures can withstand pinning of sessile droplets and remain super-hydrophobic for a longer time than their non-hierarchical counterparts. The effect is documented by recording the water contact angles of sessile droplets during their evaporation from the surfaces. The surface morphology is mapped by atomic force microscopy (AFM) and used together with the theory of Miwa et al. to estimate the degree of water impregnation into the surface structures. Finally, the different behavior during the droplet evaporation is discussed in the light of the obtained water impregnation levels.

scholarly journals Characterization of Absorption Losses and Transient Thermo-Optic Effects in a High-Power Laser System

Photonics ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 94
Author(s):  
Lukasz Gorajek ◽  
Przemyslaw Gontar ◽  
Jan Jabczynski ◽  
Jozef Firak ◽  
Marek Stefaniak ◽  
...  
Keyword(s):  
High Power ◽  
Continuous Wave ◽  
Beam Quality ◽  
Laser System ◽  
Infrared Camera ◽  
High Energy ◽  
Laser Source ◽  
Transient Temperature ◽  
Temperature Profiles ◽  
Beam Diameter

(1) Background: The modeling, characterization, and mitigation of transient lasers, thermal stress, and thermo-optic effects (TOEs) occurring inside high energy lasers have become hot research topics in laser physics over the past few decades. The physical sources of TOEs are the un-avoidable residual absorption and scattering in the volume and on the surface of passive and active laser elements. Therefore, it is necessary to characterize and mitigate these effects in real laser systems under high-power operations. (2) Methods: The laboratory setup comprised a 10-kW continuous wave laser source with a changeable beam diameter, and dynamic registration of the transient temperature profiles was applied using an infrared camera. Modeling using COMSOL Multiphysics enabled matching of the surface and volume absorption coefficients to the experimental data of the temperature profiles. The beam quality was estimated from the known optical path differences (OPDs) occurring within the examined sample. (3) Results: The absorption loss coefficients of dielectric coatings were determined for the evaluation of several coating technologies. Additionally, OPDs for typical transmissive and reflective elements were determined. (4) Conclusions: The idea of dynamic self-compensation of transient TOEs using a tailored design of the considered transmissive and reflecting elements is proposed.

scholarly journals Fabricating Laser-Induced Periodic Surface Structures on Medical Grade Cobalt–Chrome–Molybdenum: Tribological, Wetting and Leaching Properties

Lubricants ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 70 ◽  
Author(s):  
Sanne van der Poel ◽  
Marek Mezera ◽  
Gert-willem Römer ◽  
Erik de Vries ◽  
Dave Matthews
Keyword(s):  
Spatial Frequency ◽  
High Spatial Frequency ◽  
Hierarchical Structures ◽  
Surface Structures ◽  
Hazardous Substances ◽  
Laser Source ◽  
Hip Implants ◽  
Periodic Surface ◽  
Cobalt Chrome ◽  
Counter Surface

Hip-implants structured with anti-bacterial textures should show a low-friction coefficient and should not leach hazardous substances into the human body. The surface of a typical material used for hip-implants, namely Cobalt–Chrome–Molybdenum (CoCrMo) was textured with different types of laser-induced periodic surface structures (LIPSS)—i.e., low spatial frequency LIPSS (LSFL), hierarchical structures consisting of grooves superimposed with high spatial frequency LIPSS (HSFL) and Triangular shaped Nanopillars (TNP)—using a picosecond pulsed laser source. The effect of LIPSS on the wettability, friction, as well as wear of the structures, when slid against a polyethylene (PE) counter surface and biocompatibility was analyzed. Surfaces covered with LSFL show superhydrophobicity and grooves with superimposed HSFL, as well as TNP, show hydrophobic behavior. The coefficient of friction (CoF) of LIPSS against a polyethylene (PE) counter surface was found to be higher (ranging from 0.40 to 0.66) than the CoF of (polished) CoCrMo, which was found to equal 0.22. It was found that the samples release cobalt within biocompatible limits. Compared to polished reference surfaces, LIPSS cause higher friction of CoCrMo against PE contact. However, the wear of the PE counter surface only increased significantly for the LSFL textures. For these reasons, it is concluded that LIPSS are not suitable for a heavily loaded metal-on-plastic bearing contact.

Detailed Assessments of Tribological Properties of Binder Jetting Printed Stainless Steel and Tungsten Carbide Infiltrated with Bronze

Wear ◽  
2021 ◽  
pp. 203788
Author(s):  
Shaogang Cui ◽  
Shenglu Lu ◽  
Kiet Tieu ◽  
Ganesh Kumar Meenashisundaram ◽  
Long Wang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Tungsten Carbide ◽  
Tribological Properties ◽  
Binder Jetting ◽  
And Tungsten
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