PhD defense ceremony Marek Mezera on Oct. 16th 2020

Marek Mezera an Early Stage Researcher (ESR), will defend his PhD-thesis on October 16th, starting at 16:30 o’clock in room 4 of the Waaier building of the University of Twente in The Netherlands. Supervised by Gert-willem Römer and Dave Matthews, he carried out most of his work at the Chair of Laser Processing at the University of Twente. Below is a summary of the work and results of Marek.


The interaction of an object with its surroundings depends firstly on the object’s surface, which determines its surface properties due to its chemical properties and macro- and microscopic structures on the surface. Earth’s flora and fauna offers a vast collection of different specialized surface properties due to (hierarchical) micro- and nanostructures. These natural examples serve as a catalog for scientists and product designers who aim for replicating those properties. A one-step method to produce highly regular (hierarchical) nanostructures is to create Laser-induced Periodic Surface Structures (LIPSS). Although extensively studied in the last half century, LIPSS manufacturing did not emerge from an experimental status into industrial applications due to scientific and technical challenges. In this thesis, a picosecond pulsed laser source is evaluated for the potential of processing a large portfolio of LIPSS on different types of materials. Therefore, six research topics are addressed. First, the feasibility of processing LIPSS on polymers using a picosecond pulsed laser source was studied. It was found, that LIPSS can be indeed be processed on two most prominent polymers (polycarbonate and polystyrene) using picosecond pulsed laser sources. The wavelength range, at which LIPSS production was possible was found to be wider than for nanosecond pulsed laser sources, but not as wide as for femtosecond pulsed laser sources. However, the range of peak fluence levels and number of pulses impinging one spot needed to produce LIPSS are found to be similar for all laser pulse durations. Second, the influence of the bulk temperature of a thermoplastic polymer (polycarbonate) on the formation of LIPSS using a picosecond pulsed laser source was investigated. It was found that the peak fluence levels at which LIPSS form decrease with increasing bulk temperature. However, the bulk temperature did not influence the number of pulses impinging one spot necessary for LIPSS development. From this, it can be concluded, that the development of so-called Low Spatial Frequency LIPSS of type II (LSFL-II) is an accumulative process, depending on the number of pulses and that LIPSS formation is strongly affected by the local sample temperatures reached and by the involved strong variations of the polymer viscosity. Third, the formation of LIPSS on a pre-structured polymer (polycarbonate) was examined in order to achieve hierarchical micro-/nano-surface structures. It was found that LIPSS can be formed on top of various forms and sizes of micrometer-sized Direct Laser Interference Patterning (DLIP) structures (ridges) by selecting the laser beam polarization perpendicular to the pre-structured microscopic ridges. Since LIPSS only form in a narrow window of laser fluence levels, the growth of LIPSS only on top of the pre-structured microscopic ridges was limited by the non-normal angle of incidence of the laser radiation at the side walls of the microscopic ridges. Fourth, the feasibility of producing all types of LIPSS known to form on metals due to femtosecond laser pulses, by using a picosecond laser source, with different types of laser polarizations on a medical-grade cobalt-chrome-molybdenum alloy was explored. It was found that indeed all of LIPSS types which form due to femtosecond laser pulses on metals can be produced using picosecond laser pulses. Fifth, a mathematical model was developed to predict the homogeneity of large areas | i.e. larger than the area of a laser spot | of LIPSS depending on laser processing parameters and material constants. The model was validated by experiments on silicon. This model can also be used to optimize laser processing parameters to decrease the production time for large areas of LIPSS. It was concluded, that the model is a convenient tool, which can be exploited for determining the process parameters necessary for the production of large homogeneous areas of LIPSS at the shortest possible production time. Last, it was shown that the LIPSS production time for Low Spatial Frequency LIPSS of type I (LSFL-I) can be further decreased by defocused laser processing. That is, it was shown experimentally that LIPSS produced on silicon do not differ in periodicity and height when processing in focus, or below or above the focus of the laser beam. Hence, to further increase production rates of LIPSS, defocused laser processing is a viable approach.

PhD degree awarded to Antonio García Girón

On 28th February 2020, our Early Stage Researcher Antonio García Girón, from the Laser4Fun project, successfully defended his thesis for the degree of Doctor of Philosophy.

The work titled “Laser-based surface functionalisation: advances in durability and 3D processing” was carried out in the University of Birmingham under the supervision of Professor Stefan Dimov, studying some limitations of the laser surface functionalisation. The examination board was composed by Dr. C. Kong, Dr. S. Bigot and Dr. N. Gao, and the viva took place at the University of Birmingham in the morning on 28th February 2020.

Summary of Antonio’s research
Surface functionalization is gaining interests for industry and research due to the new attractive properties that can be “imprinted” on metal components, e.g. bacteria repellence or hydrophobicity among others. Considering the available alternative technologies to achieve such functional responses, direct laser writing is gaining a popularity due to its cost-effectiveness, selectivity and relatively short processing time. It allows surface properties to be modified or tuned by patterning and texturing at micron or submicron scales. However, laser surface functionalization has some limitations, too, such as the durability of the produced topographies and hence of their functionality, and also capabilities to apply it on free-form surfaces. In this context, the focus of the research presented in this thesis is on addressing these open issues. In particular, a combination of plasma surface alloying and laser patterning is proposed in order to increase hardness of produced functional surfaces, and thus to increase their wear resistance and durability. Also, a method to study the effects of the process disturbances in patterning 3D surfaces is proposed, especially on resulting topographies and their functional responses. All together, the research advances the knowledge in laser surface patterning and addresses key constraints for the broader use of this technology by industry.

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

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

van der Poel, S.H., Mezera, M., Römer, G.R.B.E., de Vries, E.G., Matthews, D.T.A., Fabricating Laser-Induced Periodic Surface Structures on Medical Grade Cobalt–Chrome–Molybdenum: Tribological, Wetting and Leaching Properties. Lubricants  2019, 7(8), 70. 


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.


PhD degree awarded to Jose Cardoso and Daniel Huerta Murillo

On April 11, Jose Cardoso and Daniel Huerta successfully defended their PhD thesis and were awarded the degree of PhD.

Jose Cardoso and Daniel Huerta Murillo were PhD candidates and Early Stage Researchers in the Laser4Fun project. They were the third and fourth (out of thirteen) PhD candidates from the Laser4Fun project to be awarded with the PhD degree.

The doctoral thesis were developed on the Laser Centre under the direction of Dr. José Luis Ocaña and the public defense of the doctoral thesis took place on April 11th 2019 at the School of Industrial Engineering of the Polytechnical University of Madrid (ETSII – UPM). The defense court was formed by Dr. Jesus de Vicente y Oliva as President, Dr. Henryk Fiedorowicz, Dr. Francisco Javier Ester Sola and Dr. Antonio Gimenez Fernandez as Vocals and Dr. Angel Garcia Beltran as Secretary.


First annual Laser4Fun meeting

The annual LASER4FUN meeting, as well as the Supervisory Board (SB) meeting of the LASER4FUN project took place on June 23rd and 24th, 2016 in Bordeaux, France. The meeting was hosted by ALPhaNOV. As it was the first meeting where all the Early Stage Reseachers (ESRs) joined, the ESRs introduced themselves and presented their background. They also joined the discussions on the progress and future work of the project with their supervisors & industrial partners, and had their first training. Moreover, the specifications and requirements of the surfaces to be produced/studied (Workpackage 1), were discussed. Further, the status of the project, management and reporting issues, as well as communication and dissemination topics were discussed.

All participants of the 1st Annual LASER4FUN meeting in Bordeaux (F).
All participants of the 1st Annual LASER4FUN meeting in Bordeaux (F).

All 14 ESRs recruited!

The LASER4FUN European Training Network had 14 vacancies for Early Stage Researchers (ESRs) for research positions in the frame of a PhD doctoral programme, targeting a PhD degree. The consortium is happy to announce that all ESR positions have been filled and that the ESRs have started their work between January 1st and May 2nd 2016. The biography of each ESR can be found on the PEOPLE page on this website.

All Eary Stage Researchers (ESRs) at the 1st Annual LASER4FUN meeting (June 23-24, 20160 in Bordeaux, France
All Eary Stage Researchers (ESRs) at the 1st Annual LASER4FUN meeting in Bordeaux, France