Publication

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

Vittorio Vercillo, Norbert Karpen, Alexandre Laroche, Javier Alejandro Mayén Guillén, Simone Tonnicchia, Raphaelde Andrade Jorge, Elmar Bonaccurso (2019) Analysis and modelling of icing of air intake protection grids of aircraft engines. Cold Regions Science and Technology, Volume 160, April 2019, Pages 265-272.

Abstract

Icing represents a major problem in the aviation industry. While icing of aerodynamic surfaces such as airfoils due to the impingement of supercooled liquid water droplets is widely studied, even if not yet fully understood, icing of supporting structures like protection grids of engine air intakes has been investigated to a lesser extent. An optimization of the design of the grids will help to reduce icing severity and delaying or avoiding loss of efficiency that could lead to hazardous situations. The present study investigates the icing behaviour of stainless steel protection grids in use on rotorcraft and turboprop engines. New experimental and analytical tools were developed to enable a quantitative study of grid icing under representative icing conditions in a lab-scale icing wind tunnel. The variation of the most relevant parameters like liquid water content of the cloud, airspeed, ambient temperature and mesh size of the grid allowed the identification of their influence on the icing behaviour. Further analysis of the experimental data led to the development and validation of a general physical model for ice accretion on grid structures.

Link(s)

• https://www.sciencedirect.com/science/article/pii/S0165232X18304415
• https://doi.org/10.1016/j.coldregions.2019.01.012

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

Marek Mezera and G.R.B.E. Römer. Upscaling laser-induced periodic surface structures (LIPSS) manufacturing by defocused laser processing, Proc. SPIE 10906, Laser-based Micro- and Nanoprocessing XIII, 109060U (4 March 2019); doi: 10.1117/12.2510004

Abstract

Low spatial frequency Laser-induced Periodic Surface Structures (LSFL) have been created on single crystal silicon with picosecond laser pulses with a wavelength of λ =1030nm with varying laser spot diameters obtained by a defocused laser beam. The laser processing parameters have been adjusted theoretically and experimentally to obtain similar LSFL for all studied laser spot diameters. The periodicity and amplitude of the LSFL were measured by SEM and AFM analysis. It has been found that the periodicities of the LSFL do not change when LSFL were created with larger laser spot diameters. The amplitudes of the LSFL decrease with increasing laser spot diameters, although this correlation is not strong.

Links:

DOI: 10.1117/12.2510004

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

Marek Mezera and G.R.B.E. Römer. Model based optimization of process parameters to produce large homogeneous areas of laser-induced periodic surface structures, Opt. Express 27, 6012-6029 (2019); doi: 10.1364/OE.27.006012

Abstract

A model is presented, which allows to predict the (in)homogeneity of large areas covered with Laser-induced Periodic Surface Structures (LIPSS), based on the laser processing parameters (peak laser fluence and geometrical pulse-to-pulse overlap) and experimentally determined material properties. As such, the model allows to establish optimal processing conditions, given the material properties of the substrate to be processed. The model is experimentally validated over a large range of geometrical pulse-to-pulse overlap values and fluence levels on silicon using a picosecond laser source.

Links:

DOI: 10.1364/OE.27.006012

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

J.-M. Romano, M. Gulcur, A. Garcia-Giron, E. Martinez-Solanas, B.R. Whiteside and S.S. Dimov. Mechanical durability of hydrophobic surfaces fabricated by injection moulding of laser-induced textures. Applied Surface Science 476 (2019) 850-860

Abstract

The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces’ functional response.

Link(s)

• https://doi.org/10.1016/j.apsusc.2019.01.162

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

L. Capuano, D. de Zeeuw and G.R.B.E. Römer. Towards a Numerical Model of Picosecond Laser-Material Interaction in Bulk Sapphire. JLMN-Journal of Laser Micro/Nanoengineering Vol. 13, No. 3, 2018

Abstract

Crystalline sapphire (Al2O3) is a hard and transparent material widely used in industry. When applying IR laser wavelengths, sapphire can be laser-processed inside the bulk (sub-surface) to produce 3D structures, which can find uses, for example, in the production of microfluidic devices. Ultrashort and tightly focused laser pulses trigger several energy absorption mechanisms inside the bulk. The absorbed energy locally modifies the structure of sapphire. Existing (numerical) models of sapphire laser processing describe mainly femtosecond pulsed laser-material interaction (most of them only addressing surface processing) and, in addition, these models do not simulate the laser-induced temperatures of the lattice. Therefore, this study is aimed at a 2D-axisymmetric, time dependent, numerical model of the physics in picosecond laser-material interaction with sapphire. The physical phenomena in model include, but are not limited to: multiphoton absorption, tunneling ionization, avalanche ionization, recombination of carriers, diffusion of carriers and heat diffusion. Based on these phenomena, three quantities are calculated, namely: electron density, electron temperature and lattice temperature. The model was implemented in COMSOL Multiphysics®. It was found that, sapphire is modified by the laser radiation only if avalanche ionisation is triggered in the bulk.

Link

DOI: 10.2961/jlmn.2018.03.0005

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

F. Fraggelakis, G. Mincuzzi, J. Lopez, I. Manek-Hönninger and R. Kling. Controlling 2D laser nano structuring over large area with double femtosecond pulses. Applied Surface Science, November 2018

Abstract

Laser surface texturing is an established way to introduce surface functionalities on solid surfaces. By means of femtosecond laser sources, it’s possible to texture a variety of solids such as metals, semiconductors and transparent materials, introducing features of different symmetry and size. Fabrication of laser induced periodic surface structure (LIPSS) which typically range in the near-submicron length scale can lead to strong modifications of surface wetting, tribological and optical properties. Controlling LIPSS morphology could enable us to mimic functional textures found in nature, introducing functionalities such as antireflectivity and bactericidity. Several works demonstrate the impact of polarization control and double-pulse irradiation on determining texture symmetry and size. Here we present a comprehensive study on controlling laser induced structures by double femtosecond pulse irradiation. The effect of pulse polarization and interpulse delay is elucidated and the generation of novel 2D surface morphologies is reported. A plausible interpretation of the structure formation mechanism is proposed in the frame of non-linear convection flow. A high average power industrial femtosecond laser source with a pulse duration of 350 fs operating at high repetition rate was employed for the experiments. Large areas were processed by combining different 2D morphologies generating a holographic pattern. We believe that our results provide a novel insight in controlling laser induced submicron morphology. Moreover, the presented surface texturing process is scalable in terms of processed area and cycle time and fully compatible with high repetition rates, demonstrating for the first time the feasibility to introduce double-pulse processing in an industrial environment.

Link(s)

• https://doi.org/10.1016/j.apsusc.2018.11.106

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

L. Capuano, R. Pohl, R. M. Tiggelaar, J. W. Berenschot, J. G. E. Gardeniers, and G. R. B. E. Römer, “Morphology of single picosecond pulse subsurface laser-induced modifications of sapphire and subsequent selective etching” Opt. Express26, 29283-29295 (2018)

Abstract

The effect of 1030nm single picosecond pulsed laser-induced modification of the bulk of crystalline sapphire using a combined process of laser amorphization and selective wet chemical etching is studied. Pulse durations of more than 1 picosecond are not commonly used for this subsurface process. We examine the effect of 7 picosecond pulses on the morphology of the unetched, as well as etched, single pulse modifications, showing the variation of shape and size when varying the pulse energy and the depth of processing. In addition, a qualitative analysis of the material transformation after irradiation is provided as well as an analysis of cracking phenomena. Finally, a calculated laser intensity profile inside sapphire, using the Point Spread Function (PSF), is compared to the shape of the modifications. This comparison is employed to calculate the intensity threshold leading to amorphization, which equals 2.5⋅10¹⁴ ± 0.4⋅10¹⁴ W/cm².

Links:

DOI: 10.1364/OE.26.029283

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

Marek Mezera, Martin van Drongelen and G.R.B.E. Römer. Laser-Induced Periodic Surface Structures (LIPSS) on Polymers Processed with Picosecond Laser Pulses, Journal of Laser Micro/Nanoengineering  Vol. 13, No. 2, 2018; doi: 10.2961/jlmn.2018.02.0010

Abstract

Based on a literature review, it was concluded that Laser-induced Periodic Surface Structures (LIPSS) on polymers are produced when applying laser sources operating either in the ultraviolet wavelength and nanosecond pulse duration, or radiation of wavelengths ranging from 265nm to 1045nm and pulse durations in the femtosecond regime. LIPSS were not reported when using pico-second laser sources. The purpose of this paper is to study whether (and if so which) LIPSS form on polymers when picosecond pulsed laser source is applied. Low Spatial Frequency LIPSS (LSFL) and High Spatial Frequency LIPSS (HSFL) have been obtained on polycarbonate and on polystyrene when applying picosecond laser pulses at a wavelength of 343nm on single spots and on processed lines. When using a wavelength of 515nm, LSFL and HSFL have been produced only on polycar-bonate, but also led to porosity of the structured area.

Links:

DOI: 10.2961/jlmn.2018.02.0010

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

Antonio Garcia-Giron, Jean-Michel Romano, Y. Liang, Behnam Dashtbozorg, Hanshan Dong, Pavel Penchev, Stefan Dimov. Combined Surface Hardening and Laser Patterning for Producing Wear Resistant Hydrophobic Surfaces. 2nd World Congress on Micro and Nano Manufacturing (September 2018); doi: 10.3850/978-981-11-2728-1_16

Abstract

This work 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 carburised stainless steel plates and at the same time to functionalise them to obtain super-hydrophobic properties.

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

Jean-Michel Romano, Rajib Ahmed, Antonio Garcia-Giron, Pavel Penchev, Olivier Dellea, Stefan Dimov. Towards Large Area Submicron Surface Texturing by Femtosecond Laser Irradiation of Microparticle Arrays. 2nd World Congress on Micro and Nano Manufacturing (September 2018); doi: 10.3850/978-981-11-2728-1_10

Abstract

The direct laser submicron texturing of X6Cr17 stainless steel plates is reported. A hexagonal close-packed monolayer of 1um transparent silica microspheres deposited onto the metallic surface was irradiated with near-infrared femtosecond laser source to generate an array of Photonic Jets (PJ). The PJ intensity profiles were calculated by simulation. PJ full width at half maximum was estimated to be ~500nm on the surface. The influence of pulse energy and focal offset on material removal and microspheres’ ejection was studied. Different 1um-periodic submicron topographies were fabricated by a single-shot irradiation, i.e. ranging from 30nm-height bumps to 200nm-to-1um diameter holes. Consecutive multi pulse processing generated triangular laser-induced surfaces structures (LIPSS). In addition, the dry laser cleaning effect and large area texturing employing PJ were investigated.