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International audience; Microstructured antireflective coatings (ARCs) can reduce reflection losses over a wide range of incidence angles when applied to the surface of a high-efficiency III-V photovoltaic cell in a concentrator photovoltaic (CPV) system. In this article, we present a microstructured ARC consisting of a monolayer of close-packed silica microbeads partially submerged within a polydimethylsiloxane (PDMS) cell encapsulant for use within a reference 500Â CPV submodule. Comparing a commercialized SiO x encapsulant to this microstructured coating with 25% submerged 1,000 nm-diameter beads, angle-dependent external quantum efficiency measurements yield a 2.6% current gain for the microstructured coating. Simulations demonstrate good agreement with measurements, predicting a 2.4% current gain for the same configuration. Extrapolating with our validated model, we estimate a maximum and achievable (within a large manufacturing tolerance) current gain of 3.4% and 2.9 ± 0.4% using 60% submerged and 10%-32% submerged 760 nm-diameter beads, respectively.

Glass is one of the most important technical surfaces for numerous applications in automotive, optical, and consumer industries. In addition, by producing textured surfaces with periodic features in the micrometre range, new functions can be created. Although laser-based methods have shown to be capable to produce structured materials in a wide amount of materials, due to its transparency large bandgap dielectrics can be only processed in a controlled manner by employing high-power ultra-short pulsed lasers, thus limiting the employable laser sources. In this article, an interference-based method for the texturing of soda-lime glass using a 15 ns pulsed (1 kHz repetition rate) infrared (1053 nm) laser is proposed, which allows fabricating different periodic patterns with micrometre resolution. This method consists on irradiating a metallic absorber (stainless steel) put in direct contact with the glass sample and inducing locally an etching process on the backside of the glass. Then, the produced plasma at the interference maxima positions leads to the local fabrication of well-defined periodic line-like and dot-like surface patterns. The produced patterns are characterised using white light interferometry and scanning electron microscopy.

Nowadays, functionalized surfaces become more and more important for industrial applications concerning wettability, ice-repellency, self-cleaning, or tribology. In this contribution, an innovative approach is presented using the direct laser interference patterning (DLIP) technique for tailoring the wettability of copper surfaces. The interference of the laser beams was conducted by using prisms for forming a like-like pattern with a spatial period Λ of 3.3 µm. Moreover, texture depths up to 1.01 µm were reached. The wettability could be set to static water contact angles between 120° and 150° This paper gives inside into the viability of structuring copper materials using a low-cost nanosecond laser source in combination with an innovative beam shaping setup.

This work reports the synthesis and characterization of a series of new degradable ethynyl-ended polylactides with different architectures. These ethynyl-functionalized polylactides were blended with a commercial low molar mass tetrathiol to prepare crosslinked polymeric networks by a thiol-yne photoclick reaction that was studied by infrared spectroscopy and photocalorimetry. Cell proliferation assays with human colorectal carcinoma cells showed that the resulting polymeric networks are not cytotoxic. Two-dimensional structures were prepared by patterned curing using direct laser writing of the photopolymerizable formulations. Preliminary cell tests on substrates provided with these polymeric structures demonstrate the possibility to generate cell patterns., This work was supported by the MINECO, Spain, under the project MAT2014-55205-P, SAF2014-54763-C2-2-R, FEDER funding and Aragón Government-FSE (Research Groups E04 and E93). The authors would also like to acknowledge the use of the CEQMA Services (Nuclear Magnetic Resonance, Mass Spectra, Surface and Coatings Characterization and Thermal Analysis) of the Universidad de Zaragoza-CSIC. A. Concellón thanks MINECO for his PhD grant. L. Asín acknowledges her Juan de la Cierva fellowship.

International audience; The study of mechanotransduction signals and cell response to mechanical properties requires designing culture substrates that possess some, or ideally all, of the following characteristics: (1) biological compatibility and adhesive properties, (2) stiffness control or tunability in a dynamic mode, (3) patternability on the microscale and (4) integrability in microfluidic chips. The most common materials used to address cell mechanotransduction are hydrogels, due to their softness. However, they may be impractical when complex scaffolds are sought and they lack viscous dissipative properties that are very important in mechanobiology. In this work, we show that an off-the-shelf, biocompatible photosensitive glue, Loctite 3525, may be used readily in mechanobiology assays without any special treatment prior to fabrication of cell culture platforms. Despite a high (MPa) stiffness easily tunable by UV exposure time at a fixed dose, 3T3 fibroblasts showed a response to the mechanics of the material similar to that obtained on much softer (kPa) hydrogels. Loctite's viscous dissipation properties indeed seemed to be responsible for such cell mechanical response, as suggested by recent works where more complex two-phase hydrogels were employed. More interestingly, it was possible to stiffen soft Loctite substrates by post-exposing them during cell culture, to observe changes in cell spreading caused by a dynamic stiffness modification. Thanks to Loctite 3525's patternability, micropillars were also fabricated to demonstrate the compatibility with traction force microscopy studies. Finally, the glue was used as an excellent adhesion layer for hydrogels on glass or PDMS, without the need for additional treatment, enabling the easy fabrication of microfluidic chips integrating hydrogels.

Ion micro beam was employed to fabricate microstructures based on poly(dimethylsiloxane) (PDMS). Carbon ions with energy of 6.0 MeV were used. The ion treatment induces modifications in PDMS surface and on the optical properties as a function of the ion current and fluence. PDMS foils were produced from commercially available two component addition materials. The selective modifications of the polymer were studied for applications in micro-fluids, micro-optics and micro-electronics. The comparison between the unirradiated and irradiated PDMS was investigated in morphology and compactness using the atomic force microscopy. The wetting ability of the PDMS surface was also analyzed as a function of the ion microbeam irradiation. The compositional and optical changes in PDMS were monitored by Rutherford backscattering spectrometry, elastic recoil detection analysis and optical spectroscopy measurements.

Ice accretion on external surfaces of aircraft due to the impingement of supercooled liquid water droplets can be tackled by the implementation of icephobic surfaces. Among these, superhydrophobic surfaces represent a promising solution, due to their water repellent nature. In the last decade, short/ultra-short pulsed laser technologies have been proposed as a one-step process to manufacture superhydrophobic surfaces. However, the effectiveness and durability of such surfaces in operational icing conditions has not yet been validated. In this work, we investigate ice adhesion strength and the chemical stability of metal alloys textured with a UV nanosecond laser via Direct Laser Writing. Keywords: Superhydrophobic, Icephobic, Icing, Laser, Microstructuring, Durability

Laser Assisted Net Shape Engineering : 9 International Conference on Photonic Technologies : Proceedings of the LANE 2016 September 19-22, 2016 Fürth, Germany / Edited by M. Schmidt, F. Vollertsen and C. B. Arnold 9 International Conference on Photonic Technologies, Fürth, Germany, 19 Sep 2016 - 22 Sep 2016; Amsterdam [u.a.] : Elsevier, Physics procedia, 83, 1118-1129 (2016). doi:10.1016/j.phpro.2016.08.117, Published by Elsevier, Amsterdam [u.a.]

A technique for patterning compact thin metal layers is presented. The technique is based on a successive application of well known, cost-effective, and simple methods of glass poling and electric field assisted dissolution. A microstructure from the patterned anode was copied onto a thin silver layer on a glass substrate. It is demonstrated that electric field assisted dissolution can be used for selective dissolution of compact metal layers. Nanostructuring of compact metal layers is interesting as it can be used in the production of metamaterials, metasurfaces, and optical circuits. The proposed two-step technique does not involve expensive equipment, and the duration of the structuring process is independent of the size of the required structured surface.

The microstructuring of the distribution of silver nanoparticles (NPs) in mesoporous titania films loaded with silver salts, using two-beam interference lithography leading to 1 Dimension (1D) grating, induces variations in the photocatalytic efficiency. The influence of the structuration was tested on the degradation of methyl blue (MB) under ultraviolet (UV) and visible illumination, giving rise to a significant improvement of the photocatalytic efficiency. The periodic distribution of the NPs was characterized by transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and scanning electron microscopy (SEM).

Novel ion beam–based method induces superconductivity in Weyl semimetal microstructures., By introducing a superconducting gap in Weyl or Dirac semimetals, the superconducting state inherits the nontrivial topology of their electronic structure. As a result, Weyl superconductors are expected to host exotic phenomena, such as nonzero-momentum pairing due to their chiral node structure, or zero-energy Majorana modes at the surface. These are of fundamental interest to improve our understanding of correlated topological systems, and, moreover, practical applications in phase-coherent devices and quantum applications have been proposed. Proximity-induced superconductivity promises to allow these experiments on nonsuperconducting Weyl semimetals. We show a new route to reliably fabricate superconducting microstructures from the nonsuperconducting Weyl semimetal NbAs under ion irradiation. The significant difference in the surface binding energy of Nb and As leads to a natural enrichment of Nb at the surface during ion milling, forming a superconducting surface layer (Tc ~ 3.5 K). Being formed from the target crystal itself, the ideal contact between the superconductor and the bulk may enable an effective gapping of the Weyl nodes in the bulk because of the proximity effect. Simple ion irradiation may thus serve as a powerful tool for the fabrication of topological quantum devices from monoarsenides, even on an industrial scale.

Natural polymers, such as hyaluronan, are considered as good candidates to substitute synthetic materials in many biological applications due to their intrinsic biocompatibility for in vitro and living cell experiments. This work describes surface modifications performed over modified hyaluronan derivatives which could help to understand the physical and biochemical cues on the cell-behaviour. A photocrosslinkable methacrylated hyaluronan was microstructured using soft lithography techniques to obtain a microenvironment suitable for cell-behaviour experiments, which might mimic the extra-cellular matrix. In addition, sulphated and non-sulphated oxidized hyaluronan were immobilized on bare substrates and micrometric features of cell adhesive and non-adhesive proteins were patterned by microcontact printing on top of them. The obtained structures were characterized by optical microscopy, profilometry and atomic force microscopy. The stability of structures was tested by immersion in physiological salt solutions. The observed results prove the suitability of the materials and protocols described., This work was supported and carried out under the scope of the European Project Find and Bind (NMP4-SL-2009-229292).

International audience; Here we present the synthesis of titania-based microwires through an electrolytic deposition process using a scanning electrochemical microscope (SECM). The method is based on the localized hydrolysis of an aqueous precursor using the base electrogenerated on the ultramicroelectrode surface. We show that the diameter of these microwires can be controlled from the diameter of the working electrode (ultramicroelectrode of 5, 10 or 25 μm in diameter). The smallest microwire produced during this work has a mean diameter of 6.8 μm which remains uniform all along the length. Lengths of typically 880 μm were obtained after 1200 s of deposition.

The appearance of a surface can be controlled by creating periodic microstructures designed to diffract light and produce structural colors. Nevertheless, since structural coloration is based on diffraction, the produced colors have a strong dependence on the viewing angle and absence of coloration takes place while tilting the samples. In this work direct laser interference patterning is used to firstly provide transparent polymer sheets a structural coloration with a high-range observation angle, and secondly to demonstrate the combination of structural colors, producing a white coloring effect. The employed approaches are based on the fabrication of micro-gratings with multiple periods in the same structured area and on the engineering of the diffraction orders of the diffraction spectrum. The patterned surfaces are characterized by confocal microscopy and angular spectrometry in reflection mode. The morphological characterization shows homogeneous surface patterns, while the spectral results demonstrate that combining four spatial periods on a single patterned surface, a white appearance is obtained over an angular observation range higher than 30°. The experimental results are supported by theoretical predictions by means of generalized formulas based on the diffraction of light. Fil: Storm, Sebastian. Fraunhofer Institute For Material And Beam Technology; Alemania Fil: Alamri, Sabri. Technische Universität Dresden; Alemania. Fraunhofer Institute For Material And Beam Technology; Alemania Fil: Soldera, Marcos Maximiliano. Fraunhofer Institute For Material And Beam Technology; 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; Argentina Fil: Kunze, Tim. Fraunhofer Institute For Material And Beam Technology; Alemania Fil: Lasagni, Andrés Fabián. Technische Universität Dresden; Alemania