Fabrication of superhydrophobic and ice-repellent surfaces on pure aluminium using single and multiscaled periodic textures

Fabricating aluminium surfaces with superhydrophobic and ice-repellent properties present nowadays a challenging task. In this work, multifunctional structures are manufactured by direct laser writing and direct laser interference patterning methods using pulsed infrared laser radiation (1064nm). Diferent periodic patterns with feature sizes ranging from 7.0 to 50.0µm are produced. In addition, hierarchical textures are produced combining both mentioned laser based methods. Water contact angle tests at room temperature showed that all produced patterns reached the superhydrophobic state after 13 to 16 days. In addition, these experiments were repeated at substrate temperatures from −30°C to 80°C allowing to determine three wettability behaviours as a function of the temperature. The patterned surfaces also showed ice-repellent properties characterized by a near three-fold increase in the droplets freezing times compared to the untreated samples. Using fnite element simulations, it was found that the main reason behind the ice-prevention is the change in the droplet geometrical shape due to the hydrophobic nature of the treated surfaces. Finally, dynamic tests of droplets imping the treated aluminium surfaces cooled down to −20°C revealed that only on the hierarchically patterned surface, the droplets were able to bounce of the substrate.Fil: Milles, Stephan. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Technische Universität Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Voisiat, Bogdan. Technische Universität Dresden; AlemaniaFil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemania. Fraunhofer Institute For Material And Beam Technology; Alemani

Picosecond laser interference patterning of periodical micro architectures on metallic molds for hot embossing

In this work, it is demonstrated that direct laser interference patterning (DLIP) is a method capable of producing microtextured metallic molds for hot embossing processes. Three different metals (Cr, Ni, and Cu), relevant for the mold production used in nanoimprinting systems, are patterned by DLIP using a picosecond laser source emitting at a 532 nm wavelength. The results show that the quality and surface topography of the produced hole-like micropatterns are determined by the laser processing parameters, such as irradiated energy density and the number of pulses. Laser-induced periodic surface structures (LIPSS) are also observed on the treated surfaces, whose shapes, periodicities, and orientations are strongly dependent on the accumulated fluence. Finally, the three structured metals are used as embossing molds to imprint microlenses on polymethyl methacrylate (PMMA) foils using an electrohydraulic press. Topographical profiles demonstrate that the obtained structures are comparable to the masters showing a satisfactory reproduction of the texture. The polymeric microlens arrays that showed the best surface homogeneity and overall quality were those embossed with the Cr molds.Fil: Fu, Yangxi. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Technische Universität Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; ArgentinaFil: Wang, Wei. Technische Universität Dresden; AlemaniaFil: Voisiat, Bogdan. Technische Universität Dresden; AlemaniaFil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemania. Institut für Werkstoff-und Strahltechnik IWS; Alemani

Wettability control of polymeric microstructures replicated from laser-patterned stamps

In this study, two-step approaches to fabricate periodic microstructures on polyethylene terephthalate (PET) and poly(methyl methacrylate) (PMMA) substrates are presented to control the wettability of polymeric surfaces. Micropillar arrays with periods between 1.6 and 4.6 µm are patterned by plate-to-plate hot embossing using chromium stamps structured by four-beam Direct Laser Interference Patterning (DLIP). By varying the laser parameters, the shape, spatial period, and structure height of the laser-induced topography on Cr stamps are controlled. After that, the wettability properties, namely the static, advancing/receding contact angles (CAs), and contact angle hysteresis were characterized on the patterned PET and PMMA surfaces. The results indicate that the micropillar arrays induced a hydrophobic state in both polymers with CAs up to 140° in the case of PET, without modifying the surface chemistry. However, the structured surfaces show high adhesion to water, as the droplets stick to the surfaces and do not roll down even upon turning the substrates upside down. To investigate the wetting state on the structured polymers, theoretical CAs predicted by Wenzel and Cassie-Baxter models for selected structured samples with different topographical characteristics are also calculated and compared with the experimental data

Wettability control of polymeric microstructures replicated from laser-patterned stamps

In this study, two-step approaches to fabricate periodic microstructures on polyethylene terephthalate (PET) and poly(methyl methacrylate) (PMMA) substrates are presented to control the wettability of polymeric surfaces. Micropillar arrays with periods between 1.6 and 4.6 µm are patterned by plate-to-plate hot embossing using chromium stamps structured by four-beam Direct Laser Interference Patterning (DLIP). By varying the laser parameters, the shape, spatial period, and structure height of the laser-induced topography on Cr stamps are controlled. After that, the wettability properties, namely the static, advancing/receding contact angles (CAs), and contact angle hysteresis were characterized on the patterned PET and PMMA surfaces. The results indicate that the micropillar arrays induced a hydrophobic state in both polymers with CAs up to 140° in the case of PET, without modifying the surface chemistry. However, the structured surfaces show high adhesion to water, as the droplets stick to the surfaces and do not roll down even upon turning the substrates upside down. To investigate the wetting state on the structured polymers, theoretical CAs predicted by Wenzel and Cassie-Baxter models for selected structured samples with different topographical characteristics are also calculated and compared with the experimental data.Fil: Fu, Yangxi. Technische Universität Dresden; AlemaniaFil: Soldera, Marcos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas; Argentina. Technische Universität Dresden; AlemaniaFil: Wang, Wei. Technische Universität Dresden; AlemaniaFil: Milles, Stephan. Technische Universität Dresden; AlemaniaFil: Deng, Kangfa. Leibniz Institute for Solid State and Materials Research Dresden. Institute for Metallic Materials; AlemaniaFil: Voisiat, Bogdan. Technische Universität Dresden; AlemaniaFil: Nielsch, Kornelius. Leibniz Institute for Solid State and Materials Research Dresden. Institute for Metallic Materials; Alemania. Technische Universität Dresden; AlemaniaFil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemania. Fraunhofer Institute for Material and Beam Technology; Alemani

Verfahren zur Herstellung einer strukturierten Oberfläche auf einem Gegenstand

Bei dem Verfahren wird die Gesamtfläche der strukturierten Oberfläche in Teilflächen (1, 2, 3, ...., n) eingeteilt und dort wird mit Laserstrahlung ausgebildeten Strukturelementen jeweils eine periodische Struktur mit einer Strukturperiode A(d) ausgebildet, so dass von einer Beobachtungsposition (P) mehrere Teilflächen (1, 2, 3, .... , n), die in unterschiedlichen Abständen und Winkeln zur Beobachtungsposition (P) diskret zueinander angeordnet sind, jeweils eine Abbildung mit gleichem Farbeindruck mit gleicher Wellenlänge λ bei einer Bestrahlung der strukturierten Oberfläche mit weißem Licht erfass- oder erkennbar ist. Die Strukturperiode A(d) der einzelnen Teilflächen (1, 2, 3, ...., n) wird nach der Gleichungbestimmt

One-step fabrication of asymmetric saw-tooth-like surface structures on stainless steel using direct laser interference patterning

We report about the fabrication of asymmetrical periodic arrays on stainless steel by means of Direct Laser Interference Patterning. The fabrication strategy consists in irradiating the surface of the material under a certain inclination angle using a two-beam interference setup equipped with a pulsed picosecond laser system (70 ps) operating at a wavelength of 1064 nm. In particular, for tilting angles higher than 30°, well-defined saw-tooth like geometries could be produced. Due to the ultra-short duration of the laser pulses, also Laser Induced Periodic Surfaces Structures are fabricated, which create hierarchical morphologies similar to the one present in nature

Growth of regular micro-pillar arrays on steel by polarization-controlled laser interference patterning

Three-beam laser interference patterning, with the ability to control the polarization of each beam, is used to produce crater and pillar like periodic structures on steel surfaces. The experiments are performed using parallel and radial polarization vector orientations of the interfering beams. In case of parallel vector orientation, common intensity profiles consisting of intensity peaks distributed in triangle lattice geometry are formed. By changing the polarization to the radial set, the intensity distribution of the interference pattern could be inverted while the geometry also has a triangle lattice shape. The equations describing both intensity profiles are derived from the basic interference equation and the modeled interference intensity profiles are compared with measured intensity profiles. Two different types of structures containing periodically distributed craters and pillars are produced using these polarization sets. Using a detailed analysis of the scanning electron microscope images and confocal data, the mechanisms responsible of the formation of the pillar- and crater-like geometries are introduced

Efficient Water-Assisted Glass Cutting with 355 nm Picosecond Laser Pulses

In this study, the cutting of borosilicate glass plates in ambient air and water with a 355 nm wavelength picosecond laser was carried out. Low (2.1–2.75 W) and high (15.5 W) average laser power cutting regimes were studied. Thorough attention was paid to the effect of the hatch distance on the cutting quality and characteristic strength of glass strips cut in both environments. At optimal cutting parameters, ablation efficiency and cutting rates were the highest but cut sidewalls were covered with periodically recurring ridges. Transition to smaller hatch values improved the cut sidewall quality by suppressing the ridge formation, but negatively affected the ablation efficiency and overall strength of glass strips. Glass strips cut in water in the low-laser-power regime had the highest characteristic strength of 117.6 and 107.3 MPa for the front and back sides, respectively. Cutting in a high-laser-power regime was only carried out in water. At 15.5 W, the ablation efficiency and effective cutting speed per incident laser power increased by 16% and 22%, respectively, compared with cutting in water in a low-laser-power regime

High Throughput Direct Laser Interference Patterning of Aluminum for Fabrication of Super Hydrophobic Surfaces

This work addresses the fabrication of hydrophobic surface structures by means of direct laser interference patterning using an optical setup optimized for high throughput processing. The developed optical assembly is used to shape the laser beam intensity as well as to obtain the two sub beams required for creating the interference pattern. The resulting beam profile consists of an elongated rectangular laser spot with 5.0 mm × 0.1 mm size, which enables the optimized utilization of the laser fluence available from an ns-pulsed laser with a wavelength of 1064 nm. Depending on the pulse repetition rate applied, heating of the substrate volume generated by heat accumulation encouraged exceptionally high aspect ratios of the trench structures due to melt flow dynamic material deformation. Finally, water contact angle measurements of the produced structures permitted the demonstration of the capability of controlling the wetting angle, in which this effect does not only depend on the height of the generated surface structures but also on their morphology

How to get deeper structures with the same energy: Fabrication of periodic structures in stainless steel using Direct Laser Interference Patterning with burst mode ps-pulses

In this study, stainless steel substrates were treated with laser interference patterns using burst of pulses. The main objective is to evaluate their influence in the ablation mechanism using the Direct Laser Interference Patterning method. Using a 10 ps infrared laser system operating with low and high fluence levels and different pulse overlaps, a lower efficiency in the ablation process was observed for the low energy case, while at high fluences an improvement of the ablation efficiency up to 31% was observed. In addition, it was found that overlaps higher than 97.6% significantly deteriorate the pattern quality