Influence of processing parameters on surface texture homogeneity using Direct Laser Interference Patterning

Results of the work in the Laser4Fun project has been published as:

Alfredo I. Aguilar-Morales, Sabri Alamri, Tim Kunze, Andrés Fabián Lasagni. Influence of processing parameters on surface texture homogeneity using Direct Laser Interference Patterning. Optics & Laser Technology. Volume 107, November 2018, Pages 216–227.

Abstract

Surface functionalities in the field of tribology, wettability, biocompatibility and holographic marking introduced by well-defined surface structures strongly depend on the surface texture homogeneity and quality. This work presents strategies for the fabrication of homogeneous periodic surface microstructures employing the Direct Laser Interference Patterning (DLIP) technology with the fundamental transverse mode (TEM00) emitted from a nanosecond laser source. Ti6Al4V substrates are structured using line-like patterns with spatial periods of 7.20 µm, 5.82 µm and 4.31 µm. The impact of various DLIP process parameters such as laser fluence, pulse overlap, hatch distance and spatial period on the produced surface microstructures is introduced and the consequences on the surface texture homogeneity are discussed. Large-area analysis of micro structures is carried out through white light interferometry and scanning electron microscopy. A quantitative measurement scheme of the pattern homogeneity, based on topographical properties such as kurtosis, standard deviation and mean structure height was introduced. Furthermore, the influence of a second modulation arising from the employed hatch distance has been identified. A quantitative parameter, the surface error percentage, has been introduced and employed for the characterization of pattern homogeneity. It was found that specially for larger spatial periods and surfaces treated at high laser fluence, pulse-to-pulse overlaps and a short hatch distance, the overall surface texture homogeneity could be improved up to ∼80–90%.

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Airbus Group innovation in Futuris

Airbus Group innovation, an industrial partner of the Laser4Fun project, was interviewed in the TV programme Futuris from euronews. The team of Elmar Bonaccurso and Vittorio Vercillo (an ESR in the project) highlighted that the environmental-friendly manufacturing and durability of engineered surfaces with superhydrophobicity and anti-icing properties are at the centre of the preoccupation of the aerospace industry. By considering laser-texturing processes, the project Laser4Fun is offering an alternative to chemical coating of aircraft wings.

For a videoclip point your webbrowser to: http://www.euronews.com/2018/05/28/phobic2ice-an-alternative-to-chemically-de-icing-planes

Generation of micro- and nano-morphologies on a stainless steel surface irradiated with 257 nm femtosecond laser pulses

Results of the work in the Laser4Fun project has been published as:

Fotis Fraggelakis, Girolamo Mincuzzi, Inka Manek-Hönninger, John Lopez and Rainer Kling(2018) Generation of micro- and nano-morphologies on a stainless steel surface irradiated with 257 nm femtosecond laser pulses. RSC Adv., 2018, 8, 16082-16087. DOI: 10.1039/C8RA01774C.

Abstract

Surface structuring by femtosecond lasers has emerged as an efficient tool to functionalize the surfaces of various solid materials. Laser induced periodic surface structures (LIPSS) can drastically impact the wetting, friction and optical properties of the surface depending on the size, aspect ratio and period of the structures. Morphological characteristics in the nanoscale, such as nano roughness, contributing to a hierarchical surface formation are considered to have a significant impact on those properties. In this study, we demonstrate for the first time to our knowledge the feasibility of inducing ripples and spikes utilizing a 257 nm femtosecond laser. LIPSS with a period smaller than 200 nm were realised. Furthermore, we show the evolution of those structures into conical spikes for this wavelength, and we provide an interpretation on their formation. Finally, we show that sub 200 nm LIPSS can create subwavelength gratings providing non-angular dependent light reflection and non-periodic morphologies showing super hydrophobic behaviour.

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Triangular laser-induced submicron textures for functionalising stainless steel surfaces

Results of the work in the Laser4Fun project has been published as:

Jean-Michel Romano, Antonio Garcia-Giron, Pavel Penchev, Stefan Dimov (2018) Triangular laser-induced submicron textures for functionalising stainless steel surfaces. Applied Surface Science
Volume 440, 15 May 2018, Pages 162–169.

Abstract

Processing technologies that engineer surfaces with sub-micron topographies are of a growing interest to a range of optical, hydrophobic and microbiological applications. One of the promising technologies for creating such topographies employs ultra-short laser pulses to produce laser-induced periodic surface structures (LIPSS) that often result in non-regular, quasi-periodic nanoripples and nanopillars. In this research near infrared ultra-short pulses of 310 fs with a circular polarisation was used to texture ferritic stainless steel workpieces. A single-step process was designed to generate low spatial frequency LIPSS (LSFL) over relatively large areas. Apart from highly regular and homogeneous parallel lines with approximately 900 nm periodicity, extraordinarily uniform triangular-LSFL in hexagonal arrangements was created. The generation of such LSFL was found to be highly repeatable but very sensitive to the used laser processing settings. Therefore, the sensitivity of triangular-LSFL formation to the used laser processing settings, i.e. pulse to pulse distance, pulse fluence and focal plane offsets, were investigated in regard to the resulting morphologies and functional properties, i.e. structural colors and super-hydrophobicity. Finally, the capability of this technology for producing uniform triangular-shaped LSFL on relatively large surface areas of stainless steel plates was studied.

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Many contributions from Laser4Fun to 10th International Laser Symposium & International Symposium “Tailored Joining” in Dresden

The 10th International Laser Symposium & International Symposium »Tailored Joining« on February 27 & 28, 2018 was organised by the Fraunhofer IWS at the International Congress Center in Dresden, Germany. Because in the “manufacturing of the future” the digitalization of laser material processing is becoming increasingly important, the motto of the symposium was “Industry 4.0”.

During the “laser-micromachining” sessions, delegates from the Laser4Fun-consortium presented the latest results from the Laser4Fun project:

  • Gert-Willem Römer (University of Twente, The Netherlands): Laser-induced Periodic Surface Structures  (LIPPS), fundamentals and applications,
  • Antonio Ancona (CNR-IFN, Italy / University West, Sweden): Ultrafast laser surface micro-texturing to  tailor lubricated friction of steel,
  • José Luis Ocana (UPM Laser Centre, Universidad Politécnica de Madrid, Spain): Direct generation of superhydrophobic  microstructures in metals by UV laser  sources in the nanosecond regime,
  • Rainer Kling (ALPHANOV, France) Functionalization of technical surfaces with ultra-short pulsed lasers,
  • And 2 posters by Sabri Alamri and Alfredo Aguilar Morales.

Last, but not least, the Laser4Fun-delegates joined in a fruitful panel discussion about the future of laser-micromachining, together with other presenters of the micromachining session.
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2D laser induced periodic surface structures with double cross-polarized pulses

Results of the work in the Laser4Fun project has been published as:

F. Fraggelakis, G. Mincuzzi, J. Lopez, Inka Manek-Honninge, R. Kling, “2D laser induced periodic surface structures with double cross-polarized pulses,” Proc. SPIE 10520, Laser-based Micro- and Nanoprocessing XII, 105200L (19 February 2018); doi: 10.1117/12.2287841

Abstract

We present a systematic study on the generation of 2D surface structures on stainless steel, using double, crosspolarized femtosecond pulses with variable interpulse delay. We demonstrate the combined effect of the interpulse delay and key process parameters in order to obtain periodic structures. The sets of double pulses were produced utilizing a modified Michelson interferometer with interpulse delay varying from -100 ps to +2 ns. The study was carried out with an industrial laser having pulse duration of 350 fs, emitting in the near infrared (λ = 1030 nm), operating at 100 kHz coupled with a Galvo scanner. We evaluate the obtained surface morphology and structure period using SEM characterization and Fourier analysis.

Link(s)

Alfredo Aguilar Morales and Sabri Alamri attended the General Assembly of the Marie-Curie Fellows in Brussels

On February 2nd and 3rd, 2018, ESRs Alfredo Aguilar Morales and Sabri Alamri attended the 5th MCCA General Assembly of the Marie-Curie Fellows at the University of Leuven, Belgium. Both ESRs presented a poster with results of the Laser4Fun project. More info can be found at https://www.mariecuriealumni.eu/events/2018-mcaa-conference-general-assembly

Aguilar Morales at the 5th MCCA General Assembly of the Marie-Curie Fellows at the University of Leuven, Belgium (Feb. 2-3, 2018)

Sabri Alamri at the 5th MCCA General Assembly of the Marie-Curie Fellows at the University of Leuven, Belgium (Feb. 2-3, 2018)

Jean-Michel Romano columnist for AILU’s magazine

RomanoJMJean-Michel Romano, an Early Stage Researcher (ESR) in the Laser4Fun project, joined in October 2017 the Early Career Researchers (ECR) Committee of the UK Association of Industrial Laser Users (AILU). His role is to produce columns for AILU’s magazine “The Laser User” and therefore to dissimenate research activities to the laser community in the UK. More info on: http://www.ailu.org.uk/association/ecr_111217.html

Combined surface hardening and laser patterning approach for functionalising stainless steel surfaces

Results of the work in the Laser4Fun project has been published as:

A.Garcia-Giron, J.M.Romano, Y.Liang, B.Dashtbozorg, H.Dong, P.Penchev, S.S.Dimov (2018) Combined surface hardening and laser patterning approach for functionalising stainless steel surfaces. Applied Surface Science, Volume 439, 1 May 2018, Pages 516-524.

Abstract

The paper reports a laser patterning method for producing surfaces with dual scale topographies on ferritic stainless steel plates that are hardened by low temperature plasma surface alloying. Nitrogen and carbon based gasses were used in the alloying process to obtain surface layers with an increased hardness from 172 HV to 1001 HV and 305 HV, respectively. Then, a nanosecond infrared laser was used to pattern the plasma treated surfaces and thus to obtain super-hydrophobicity, by creating cell- or channel-like surface structures. The combined surface hardening and laser patterning approach allowed super-hydrophobic surfaces to be produced on both nitrided and carburised stainless steel plates with effective contact angles higher than 150°. The hardened layers on nitrided samples had cracks and was delaminated after the laser patterning while on plasma carburised samples remained intact. The results showed that by applying the proposed combined approach it is possible to retain the higher hardness of the nitrided stainless steel plates and at the same time to functionalise them to obtain super-hydrophobic properties.

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Controlling the wettability of polycarbonate substrates by producing hierarchical structures using Direct Laser Interference Patterning

Results of the work in the Laser4Fun project has been published as:

Sabri Alamri, Alfredo I. Aguilar-Morales, Andrés F. Lasagni (2018) Controlling the wettability of polycarbonate substrates by producing hierarchical structures using Direct Laser Interference Patterning. European Polymer Journal. Volume 99, February 2018, Pages 27–37.

Abstract

New strategies for the fabrication of surface structures using Direct Laser Interference Patterning are presented in this work, aiming to fabricate hierarchical structures with selective wetting properties. Polycarbonate sheets have been structured employing a two-beam interference arrangement using an ultraviolet (263 nm) nanosecond-pulsed laser, creating line- and pillar-like structures with simple and hierarchical geometries. Two different methods for producing hierarchical structures are here provided, both relying on a pixel-wise structuring technique and able to achieve high structure depths. The produced surface patterns are characterized by confocal microscopy, scanning electron microscopy and the influence of the surface topography on the water contact angle is investigated. The correlation between structure geometry and wettability response, in terms of structure height and directionality of the droplet shape is reported.

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