TY - JOUR A1 - Schwibbert, Karin A1 - Menzel, F. A1 - Epperlein, N. A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - Bacterial adhesion on femtosecond laser-modified polyethylene N2 - In this study, femtosecond laser-induced sub-micrometer structures are generated to modify polyethylene (PE) surface topographies. These surfaces were subjected to bacterial colonization studies with Escherichia coli and Staphylococcus aureus as test strains. The results reveal that the nanostructures do not influence S. aureus coverage, while the adhesion of E. coli is reduced. KW - Bacterial adhesion KW - Laser-modified surface KW - Polyethylene KW - Laser-induced nanostructures KW - Biofilm PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-492280 VL - 12 IS - 19 SP - 3107 PB - MDPI CY - Basel, Schweiz AN - OPUS4-49228 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Joseba Ayerdi, J. A1 - Slachciak, Nadine A1 - Llavori, I. A1 - Zabala, A. A1 - Aginagalde, A. A1 - Bonse, Jörn A1 - Spaltmann, Dirk T1 - On the role of a ZDDP in the tribological performance of femtosecond laser-induced periodic surface structures on titanium alloy against different counterbody materials N2 - Laser-induced periodic surface structures (LIPSS, ripples) with ~500–700 nm period were produced on titanium alloy (Ti6Al4V) surfaces upon scan processing in air by a Ti:sapphire femtosecond laser. The tribological performance of the surfaces were qualified in linear reciprocating sliding tribological tests against balls made of different materials using different oilbased lubricants. Extending our previous work, we studied the admixture of the additive 2-ethylhexyl-zinc-dithiophosphate to a base oil containing only anti-oxidants and temperature stabilizers. The presence of this additive along with the variation of the chemical composition of the counterbodies allows us to explore the synergy of the additive with the laseroxidized nanostructures. KW - Additives KW - Surface structures KW - Wear KW - Friction PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-488458 SN - 2075-4442 VL - 7 SP - 79, 1 EP - 13 PB - MDPI AN - OPUS4-48845 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Legall, Herbert A1 - Schwanke, Christoph A1 - Bonse, Jörn A1 - Krüger, Jörg T1 - The influence of processing parameters on X‑ray emission during ultra‑short pulse laser machining N2 - During ultra-short laser material processing at high laser pulse repetition rates unwanted X-ray radiation can be generated in a quantity that may constitute a potential risk for health. An adequate X-ray radiation protection requires a thoroughly understanding of the influence of the laser processing parameters on the generation of X-ray radiation. In the present work, the generated X-ray dose during laser machining was investigated in air for varying beam scanning conditions at a pulse duration of 925 fs, a center wavelength of 1030 nm and a laser peak intensity of 2.6 × 10^14 W/cm^2. The X-ray radiation dose and the corresponding spectral X-ray emission were investigated in dependence on the laser’s pulse repetition rate and on the beam scanning speed. The results show a strong dependence of the X-ray emission on these laser processing parameters. KW - Laser-induced X-ray emission KW - Ultrashort laser material interaction KW - Femtosecond laser KW - Radiation protection PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-486441 SN - 0947-8396 SN - 1432-0630 VL - 125 IS - 8 SP - 570, 1 EP - 8 PB - Springer AN - OPUS4-48644 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mezera, M. A1 - Bonse, Jörn A1 - Römer, G.R.B.E. T1 - Influence of Bulk Temperature on Laser-Induced Periodic Surface Structures on Polycarbonate N2 - In this paper, the influence of the bulk temperature (BT) of Polycarbonate (PC) on the occurrence and growth of Laser-induced Periodic Surface Structures (LIPSS) is studied. Ultrashort UV laser pulses with various laser peak fluence levels F_0 and various numbers of overscans (N_OS) were applied on the surface of pre-heated Polycarbonate at different bulk temperatures. Increased BT leads to a stronger absorption of laser energy by the Polycarbonate. For N_OS < 1000 High Spatial Frequency LIPSS (HSFL), Low Spatial Frequency LIPSS perpendicular (LSFL-I) and parallel (LSFL-II) to the laser polarization were only observed on the rim of the ablated tracks on the surface but not in the center of the tracks. For N_OS ≥ 1000 , it was found that when pre-heating the polymer to a BT close its glass transition temperature (T_g), the laser fluence to achieve similar LIPSS as when processed at room temperature decreases by a factor of two. LSFL types I and II were obtained on PC at a BT close to T_g and their periods and amplitudes were similar to typical values found in the literature. To the best of the author’s knowledge, it is the first time both LSFL types developed simultaneously and consistently on the same sample under equal laser processing parameters. The evolution of LIPSS from HSFL, over LSFL-II to LSFL I, is described, depending on laser peak fluence levels, number of pulses processing the spot and bulk temperature. KW - Laser-induced periodic surface structures (LIPSS) KW - Polycarbonate KW - Bulk temperature KW - Ultrashort laser pulses PY - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-498242 UR - https://www.mdpi.com/2073-4360/11/12/1947 SN - 2073-4360 VL - 11 IS - 12 SP - 1947 PB - MDPI CY - Basel, Switzerland AN - OPUS4-49824 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Peláez, R.J. A1 - Rebollar, E. A1 - Serna, R. A1 - Acosta-Zepeda, C. A1 - Saavedra, P. A1 - Bonse, Jörn A1 - Haro-Poniatowski, E. T1 - Nanosecond laser-induced interference grating formation on silicon N2 - The formation of gratings on the surface of a silicon wafer by nanosecond laser irradiation through a phase mask using an ArF laser emitting at 193 nm is studied. The phase mask along with some focusing optics is capable to generate via interference a periodic intensity distribution, which can be used for surface patterning. The surface patterning strongly depends on the laser energy density and on the number of pulses, as revealed by atomic force microscopy (AFM). The results show that irradiation even with a single laser pulse produces periodic depth modulations on the surface. The spatial surface modulation is in the micrometer (1.7 µm) range while the depth modulation is in the nanometer regime (1–20 nm). With an increasing number of pulses (1–100), the depth modulation amplitude increases smoothly. Increasing the number of pulses further results in the progressive destruction of the grating, vanishing completely after ~5000 pulses. This evolution is also monitored in situ by measuring the intensity of the first order-diffracted probe beam and the behavior is in accordance with what is observed by AFM. Finally, we qualitatively explain the results invoking thermally induced effects in the melted Si: these physical processes involved are probably thermocapillary and/or Marangoni effects inducing material displacement as the surface melts. KW - Nanosecond laser irradiation KW - Silicon KW - Surface modification KW - Phase mask KW - Grating PY - 2019 UR - https://iopscience.iop.org/article/10.1088/1361-6463/ab0c5f U6 - https://doi.org/10.1088/1361-6463/ab0c5f SN - 1361-6463 SN - 0022-3727 VL - 52 IS - 22 SP - 225302, 1 EP - 10 PB - IOP Publishing CY - Bristol, UK AN - OPUS4-47619 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Acosta-Zepeda, C. A1 - Saavedra, P. A1 - Bonse, Jörn A1 - Haro-Poniatowski, E. T1 - Modeling of silicon surface topographies induced by single nanosecond laser pulse induced melt-flows N2 - Irradiation with a single nanosecond laser pulse in the melting regime can result in a characteristic change in the surface morphology of crystalline silicon. This has been verified experimentally in a variety of situations, where dimple-shaped surface topographies are produced. In this work, the dimple height, depth, and width are modeled following and extending in a more rigorous manner the approach of Wood and Giles [Phys. Rev. B 23, 2923–2942 (1981)] and that of Schwarz-Selinger and coworkers [Phys. Rev. B 64, 155323 (2001)], upon varying the laser irradiation parameters such as peak energy density, pulse duration, and wavelength. This is achieved with numerical simulations of one-dimensional heat flow as input to the analytical fluid-flow equations. KW - Nanosecond laser KW - Melting KW - Silicon KW - Fluid-flow PY - 2019 U6 - https://doi.org/10.1063/1.5053918 SN - 0021-8979 SN - 1089-7550 VL - 125 IS - 17 SP - 175101-1 EP - 175101-9 PB - AIP Publishing CY - Melville, USA AN - OPUS4-47927 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -