Abstract:

Cutting-edge development of components in technological and biomedical applications requires surfaces that possess various unique properties. Diverse biological examples (e.g., lotus leaf and shark skin), developed by natural selection, often serve as inspiration for numerous surface functionalities. LaMiNaS uses laser surface engineering to fabricate bio-inspired metallic surfaces in a laboratory environment. It brings together experts from the fields of physics, analytical chemistry, mechanical engineering and photonics to develop new theoretical and experimental knowledge that will answer which surface properties should be modified and how, in order to improve materials used in: (i) erosion environments; (ii) tribological applications; (iii) cavitating fluid flows; and (iv) heat transfer applications. To provide these answers, LaMiNaS not only models and designs the functionalized surfaces by simulating natural systems, but also predicts further improvements and implements developed surfaces into engineering applications. It aims to develop theoretical knowledge explaining how laser and environmental parameters influence the unique surface properties, and clarifying the dependence of surface functionality, long-term behavior and durability on surface micro-/nanostructures and chemistry on molecular and atomic level. Experimentally, it combines advanced laser processing with different characterization techniques that can resolve topographical and chemical properties of thin and ultra-thin surface layers.

To understand the influence of intrinsic properties of laser radiation and its interaction with the material on the topographical and chemical surface modifications on micro-/nanometer scales, theoretical and experimental examination of the laser-surface interaction will address all three main regimes of laser ablation. The regime of very low fluences, where the chemical alteration of the outermost surface layer represents the main surface modification, is used to develop new approaches for controlling corrosion behavior. This does not only lead to more corrosion-resistant materials, but also enables increased corrosion to aid the development of new biodegradable materials. The regime with fluences near the ablation threshold, where laser-induced periodic surface structures (LIPSS) appear, is used for tribological applications. The underlying physical mechanisms are investigated through the development and processing of metal alloys with different crystal lattice orientations. This explains material response due to different surface densities of atoms and their influence on the thresholds for LIPSS formation. The regime of high-fluence ablation leading to diffraction-limited microstructures with high depth-to-width ratios is examined in order to functionalize surfaces for enhanced heat transfer and controlled cavitation in fluid flows. For heat transfer applications, LaMiNaS contributes to the understanding of functionalized surface behavior and long-term durability under high-frequency temperature variations due to bubble nucleation and growth during boiling. Additionally, laser surface engineering is used to develop surfaces for controlling cavitation in fluid flow. Here, the pioneering activities lead to a powerful tool for modification of the surface functions to increase (e.g., for advanced oxidation processes) or decrease (e.g., for prevention of cavitation erosion) hydrodynamic cavitation and cavitation erosion by influencing the cavitation incipience.

The LaMiNaS results facilitate more ecological technology since the developed surfaces both enhance the energy efficiency and decrease material wear. They also lead to new approaches for fabrication of smart surfaces, thus opening new possibilities to research the interactions between surfaces and light, other electromagnetic fields, molecules and atoms. In this way, LaMiNaS importantly improves the competitiveness of Slovenian and EU science and economy.

 

The phases of the project and their realization:

 

Modelling, designing and laser processing of the bio-inspired functionalized surfaces

Initial selection and optimization of surfaces [Jul 19 - Sep 19]

Optimization of processing parameters [Oct 19 - Apr 20]

Improving controllability, repeatability and scalability of the process [May 20 - Dec 20]

Laser production of surfaces (supporting activity) [Jan 21 - Jun 22]

 

Characterization of functionalized surfaces

Development of approaches for characterization of laser-processed surfaces [Jul 19 - Apr 20]

Surface characterization (supporting activity) [May 20 - Jun 22]

 

Theoretical modelling

Modelling of laser-ablation effects on surface functionalities [May 20 - Dec 20]

Verifying the models of laser ablation [Jan 21 - Jun 21]

Modelling of surface behavior and durability [Jan 21 - Sep 21]

Verifying the models of surface behavior [Oct 21 - Mar 22]

 

Testing of functional bio-inspired surfaces in engineering applications

Development of testing experimental setups and monitoring methods [Jan 21 - Jun 21]

Testing and optimization of surfaces for controlling corrosion [Jul 21 - Jun 22]

Testing and optimization of surfaces for tribological applications [Jul 21 - Jun 22]

Testing and optimization of surfaces for controlling cavitation [Jul 21 - Jun 22]

Testing and optimization of surfaces for enhanced heat transfer [Jul 21 - Jun 22]

 

The project is being implemented according to the plan.

 

Scientific papers:

M. Petkovšek, M. Hočevar, P. Gregorčič, ​Surface functionalization by nanosecond-laser texturing for controlling hydrodynamic cavitation dynamics. Ultrason. Sonochem. 67, 105126 (2020). <Press Release>

P. Gregorčič,  Comment on “Bioinspired Reversible Switch between Underwater Superoleophobicity/Superaerophobicity and Oleophilicity/Aerophilicity and Improved Antireflective Property on the Nanosecond Laser-Ablated Superhydrophobic Titanium Surfaces”. ACS Appl. Mater. Interfaces, accepted for publication (2020). <Press Release>

M. Može, M. Senegačnik, P. Gregorčič, M. Hočevar, M. Zupančič, I.Golobič. Laser-Engineered Microcavity Surfaces with a Nanoscale Superhydrophobic Coating for Extreme Boiling Performance. ACS Appl. Mater. Interfaces, accepted for publication (2020). <Press Release>

M. Hočevar, B. Šetina Batič, M. Godec, V. Kononenko, D. Drobne, P. Gregorčič. The interaction between the osteosarcoma cell and stainless steel surface, modified by high-fluence, nanosecond laser pulses. Surf. Coat. Technol. 394, 125878 (2020). <Press Release>

P. Zakšek, M. Zupančič, P. Gregorčič, I. Golobič. Investigation of nucleate pool boiling of saturated pure liquids and ethanol-water mixtures on smooth and laser-textured surfaces. Nanosc. Microsc. Therm. 24, 29-42 (2020).

M. Senegačnik, M. Jezeršek, P. Gregorčič. Propulsion effects after laser ablation in water, confined by different geometries. Applied physics A 126, 136 (2020).

M. Conradi, T. Sever, P. Gregorčič, A. Kocijan. Short- and long-term wettability evolution and corrosion resistance of uncoated and polymer-coated laser-textured steel surface. Coatings 9, 592 (2019)

 

Contributions at scientific conferences:

M. Senegačnik, M. Hočevar, B. Šetina Batič, P. Gregorčič. Laser-induced periodic surface structures : characteristics of oxide layer after ns and ps laser texturing. The 9th International LIPSS Workshop 2019, September 26-27, 2019, Ljubljana, Slovenia, (invited lecture).

M. Hočevar, P. Gregorčič, B. Šetina Batič, V. Kononenko, D. Drobne, M. Godec. Behaviour of human osteoblast-like cells on nanosecond laser-textured 316L surfaces. 27th International Conference on Materials and Technology, 16-18 October 2019, Portorož, Slovenia, (invited lecture).

M. Godec, I. Paulin, Č. Donik, M. Hočevar, J. Burja, P. Gregorčič, A. Kocijan. Different approaches to achieving biodegradability with an Fe-Mn alloy. 27th International Conference on Materials and Technology, 16-18 October 2019, Portorož, Slovenia, (invited lecture).

M. Senegačnik, N. Dominko Kobilica, M. Jezeršek, P. Gregorčič. Energy-conversion efficiency in ablative laser propulsion induced by nanosecond laser pulses. COLA 2019 - 15th International Conference on Laser Ablation, Maui-Hawaii, USA 8-13 September, 2019.

P. Gregorčič, Č. Donik, A. Kocijan. Low-fluence ablation as a tool for producing thin-layer oxides and controlling the corrosion behavior of a stainless-steel surface. COLA 2019 - 15th International Conference on Laser Ablation, Maui-Hawaii, USA 8-13 September 2019. 

L. Noč, A. Kocjan, P. Gregorčič, I. Jerman. Concentrated solar power spectrally selective absorber coatings : synthesis and characterization of new materials. 13th European Coating Symposium, September 8-11, 2019, Heidelberg, Germany.

M. Senegačnik, K. Kimura, S. Jamaguchi, P. Gregorčič, T. Sakka. Observation of cavitation bubble inner dynamics induced by pulsed laser ablation in liquids. COLA 2019 - 15th International Conference on Laser Ablation, Maui-Hawaii, USA 8-13 September 2019. 

M. Conradi, A. Kocijan, T. Sever, Č. Donik, P. Gregorčič. Short- and long-term wettability evolution and corrosion resistance of laser-textured and chemically modified steel surface. 26. međunarodni znanstveni sastanak Vakuumska znanost i tehnika, Njivice, 16.-17. svibanj 2019. Zagreb: Hrvatsko vakuumsko društvo = Croatian Vacuum Society, 2019.

 

Contributions for wider public:

P. Gregorčič. The pulse energy: a combination of an average power and a repetition rate, lectures on YouTube, 2019.

P. Gregorčič, M. Senegačnik. Surface coloration by laser-induced periodic surface structures (LIPSS), lectures on YouTube, 2019.

 

Workshops & events:

P. Gregorčič (editor). The 9th International LIPSS Workshop 2019, September 26-27, 2019, Ljubljana, Slovenia. Book of abstracts. Ljubljana: Faculty of Mechanical Engineering, 2019.

 

BSc & MSc Theses:

R. Špan. Detection system for micrometer and sub-micrometer laser drilling of thin metal foils, MSc thesis at Master's Study Programme in Mechanical Engineering (2nd Cycle of Study Programme), Ljubljana, 2019.

M. Jakič. Investigation of different strategies of laser cutting carbon-fiber reinforced polymers, BSc thesis at Professional Study Programme in Mechanical Engineering (1st Cycle of Study Programme), Ljubljana, 2019.

U. Jurjec. Laser ablation eficiency during engraving by nanosecond laser pulses, BSc thesis at  Academic Study Programme in Mechanical Engineering - Research and Development Programme (1st Cycle of Study Programme), Ljubljana, 2019. 

L. Bregar. Development of hybrid biphilic surfaces using a hydrophobic coating and laser texturing, BSc thesis at  Academic Study Programme in Mechanical Engineering - Research and Development Programme (1st Cycle of Study Programme), Ljubljana, 2019.

 

Transfer of the LaMiNaS results into the study programmes of UL:

The results were included into the the course Laser Processing Technology (Master's Study Programme in Mechanical Engineering (2nd Cycle of Study Programme), Mechatronics and Laser Engineering, 1st year, Faculty of Mechanical Engineering, UL) within the chapter Laser surface engineering.