Resonant laser printing of bi-material metasurfaces: from plasmonic to photonic optical response

Metasurfaces are nanostructured surfaces with engineered optical properties - currently impacting many branches of optics, from miniaturization of optical components to realizing high-resolution structural colors. The optical properties of metasurfaces can be traced to the individual meta-atoms, which set the nature of the optical response, e.g., plasmonic for metallic meta-atoms or photonic for dielectric meta-atoms. Combining multiple types of responses opens up new horizons in design of optical materials, but has so far been avoided due to the fabrication difficulties associated with constructing a metasurface composed of several meta-atom materials. Here, we present a multi-material design approach by optically post-processing a metasurface constructed from self-assembled polystyrene spheres coated with silver. Using our concept of resonant laser printing, we locally alter the initial plasmonic response of the meta-atoms to a pure photonic response. Our work constitutes a conceptually different way of designing metasurfaces and can pave the way for realizing multi-material metasurfaces on large areas while being cost effective.Independent Research Funding Denmark (7026-00117B); VILLUM FONDEN (17400).Peer reviewe

New techniques for the aesthetic and functional marking on polymers using laser technology

El uso de la tecnología láser está ampliamente extendido en sectores tan diferentes como el aeroespacial, la automoción, la industria maderera o la electrónica de precisión. Sus aplicaciones cubren un rango muy diverso de materiales, desde la soldadura o el corte de metales, al tratamiento superficial de plásticos o el curado de pinturas y tintas. Los procesos mediante radiación láser presentan ventajas tales como una alta coherencia y una elevada monocromaticidad. La alta densidad de energía y direccionalidad alcanzada con el láser permiten focalizar el tratamiento sobre el material con una resolución espacial mejor que 100 mm. Así mismo, se trata de una tecnología sin contacto por lo que permite evitar vibraciones además de que mediante el control numérico remoto se obtiene una gran flexibilidad durante el procesado. Sin embargo, presenta algunas desventajas a tener en cuenta, como el alto coste del equipo y el posible daño no deseado en el material.Tradicionalmente, la decoración estética de los polímeros, en concreto de aquellos usados en la gama blanca de los electrodomésticos, se ha realizado empleado técnicas como la tampografía o la estampación. Estas técnicas presentan ventajas tales como la posibilidad de usar múltiples colores o la durabilidad de la impresión. Sin embargo, adolecen de flexibilidad tanto en el proceso de impresión, donde cambiar de diseño conlleva cambiar el patrón de impresión, como en el proceso productivo, ya que es necesario un tiempo de curado de la tinta. Ambos inconvenientes dificultan notablemente la integración total del proceso de decoración en la línea de montaje.Así pues, en esta tesis se propone el estudio del marcado láser como alternativa a las técnicas tradicionales de decoración estética. En particular, se aborda un caso específico como es la decoración de las piezas plásticas estéticas de loselectrodomésticos fabricados por la compañía BSH electrodomésticos. Estos componentes se fabrican principalmente empleando el termoplástico ABS (Acrilonitrilo-Butadieno-Estireno).Así pues, se propone como primer objetivo de esta tesis:- Estudiar el tratamiento laser del ABS produciendo marcas estéticas de alta calidad. Durante este estudio se realizará la caracterización física y química de las marcas con el objetivo de optimizar el proceso de marcado. Del mismo modo, empleando las posibilidades que ofrece el láser como herramienta en el procesado de materiales, se plantea el siguiente objetivo:- Producir marcas funcionales de tal modo que se afecte a la mojabilidad del material tratando de conseguir comportamientos superhidrófobos y superhidrófilos. El control de esta propiedad es interesante para futuras aplicaciones como serían por ejemplo la limpieza de superficies o favorecer la actividad biocida. Mediante la alteración controlada de la topografía superficial del material a partir de micro-estructuración láser se busca conseguir estas propiedades. Finalmente y como parte de un estudio preliminar, se amplía el marcado estético láser con el objetivo de conseguir marcas más allá de la escala de grises, tratando de obtener una gama amplia de colores. Para ello se emplearán tres técnicas diferentes: aditivos químicos especialmente preparados para interaccionar con el láser produciendo cambio de color, procesos interferométricos de dos haces láser y reestructuración láser de superficies que presenten resonancias plasmónicas centradas en el espectro óptico visible.<br /

New techniques for the aesthetic and functional marking on polymers using laser technology

Peer reviewe

Marcado láser de polímeros blancos

Resumen del póster presentado a la 6ª Jornada de Jóvenes Investigadores en Física y Química de Aragón celebrada en Zaragoza el 20 de noviembre de 2014.Este proyecto has sido financiado por el 7 programa Marco de la unión europea dentro del proyecto UV-MARKING (http://www.uv-marking.eu/).Peer reviewe

Creation of superhydrophobic and superhydrophilic surfaces on ABS employing a nanosecond laser

This article belongs to the Special Issue Polymeric Materials: Surfaces, Interfaces and Bioapplications.A nanosecond green laser was employed to obtain both superhydrophobic and superhydrophilic surfaces on a white commercial acrylonitrile-butadiene-styrene copolymer (ABS). These wetting behaviors were directly related to a laser-induced superficial modification. A predefined pattern was not produced by the laser, rather, the entire surface was covered with laser pulses at 1200 DPI by placing the sample at different positions along the focal axis. The changes were related to the laser fluence used in each case. The highest fluence, on the focal position, induced a drastic heating of the material surface, and this enabled the melted material to flow, thus leading to an almost flat superhydrophilic surface. By contrast, the use of a lower fluence by placing the sample 0.8 µm out of the focal position led to a poor material flow and a fast cooling that froze in a rugged superhydrophobic surface. Contact angles higher than 150° and roll angles of less than 10° were obtained. These wetting behaviors were stable over time.The authors wish to thank BSH Electrodomésticos España S.A. for their financial support for this research.Peer reviewe

Influence of the wavelength on laser marking on carbon black filled ABS

Resumen del trabajo presentado al XIV Congreso Nacional de Materiales celebrado en Gijón del 8 al 10 de junio de 2016.Nowadays some processes such as welding or cutting metals, or surface treatment of plastics have been industrialized using laser systems. Therefore, thermal and chemical treatment can be strongly localized leaving the rest of material unaffected. Consequently, the laser technique allows thermally transforming heat-sensitive substrates or to process materials. In particular, aesthetic laser marking is a technological process of industrial interest. This work focus on studying the laser marking process of carbon black (CB) filled ABS plastic materials using two different laser wavelengths, 355 nm (UV) and 1064 nm (IR). The goal is to obtain white marks on dark ABS polymer surfaces, which are usually associated to a foaming effect in the polymer. The total energy deposited by both lasers has been maintained very similar to study the role of the material absorption considering the differences in the laser wavelengths. The IR laser mainly interacts with the CB, as the ABS absorption at the IR laser wavelength is very low. The energy is directly transformed in thermal energy increasing the temperature of the pigment resulting in a foam formation and a polymer pyrolisis. Moreover, the interaction of the laser can produce the degradation and elimination of the CB from the marked area improving the contrast of the mark but if the material is overexposed to the laser energy, a degradation of the structure is produced becoming a carbonization, which tends to black color, and material removing. By contrast, the mechanism in the case of the UV laser source is characterized mainly by a photochemical effect resulting in color change with negligible thermal side effects. A superficial analysis has been performed in order to study how the surface is affected by the laser irradiation. The results of the final color, topography and chemical structure of marked polymers are analyzed and compared in terms of the wavelength used. It has been demonstrated that both the amount of black additive and laser wavelength used strongly affect the aesthetical laser marking process. It can be also conclude that the laser marking process on black ABS has the potential for on line plastic processing.Peer reviewe

Direct laser interference patterning of ophthalmic polydimethylsiloxane (PDMS) polymers

The inscription of diffractive elements in ophthalmic polymers and ocular tissues to induce refractive index changes is of great interest in the fields of Optics and Ophthalmology. In this work fabrication of linear periodic patterns in polydimethylsiloxane (PDMS) intraocular lenses by means of the direct laser interference patterning (DLIP) technique was studied. A Q-Switch Nd:YAG laser coupled to second and third harmonic modules emitting linearly polarized 4 ns pulses at 355 nm with 20 Hz repetition rate was used as the laser source. Laser processing parameters were modified to produce the linear patterns. Processed samples were characterized by means of optical confocal microscopy, Scanning Electron Microscopy SEM, Energy Dispersive X-ray Spectroscopy EDX, Attenuated Total Reflectance-Infrared Spectroscopy ATR-FTIR, and Raman Spectroscopy. Depending on the laser parameters both photo-thermal and photo-chemical damage were observed in the DLIP irradiated areas. Finally, diffractive techniques were used to characterize the diffraction gratings inscribed in the samples resulting in a refractive index change of 1.9 × 10−2 under illumination of a 632.8 nm He-Ne laser.Dr. Daniel Sola thanks the Ministry of Economy and Competitiveness of the State General Administration under the project MINECO FIS2013-41237-R and the PIT2 program of the University of Murcia´s own research plan for the financial support of his contract.Peer reviewe

UV-laser marking of a TiO2-containing ABS material

Marking of titanium dioxide‐containing ABS polymeric samples was accomplished using a UV laser that induces a white to grey color change with only a minor alteration of the plastic material. The characterization of this marking process has been conducted by different techniques to determine the quality of the UV‐laser marking and to gain an insight into how the plastic material is affected by laser irradiation. Surface characterization was performed and tests were conducted to evaluate the potential applications of this UV‐marking process.Seventh Framework Programme of the European Union under the UV-MARKING project; contract grant number: 314630.Peer reviewe

Influence of the wavelength on laser marking on ABS filled with carbon black

The laser marking of acrylonitrile–butadiene–styrene filled with carbon black was studied using either an infrared or ultraviolet laser. The influence of the amount of additive on the final contrast of marks was studied for the two differentiated wavelengths. Both lasers exhibit different marking mechanisms, according to color properties, topography, and spectroscopic analysis of the marks. The infrared laser induced a thermally foaming effect and the ultraviolet laser seemed to induce a photochemical effect with the polymer matrix and removal of carbon black. The highest contrast was achieved with the infrared laser and contents of 0.1% carbon black.Financial support from EU project 7FP UV-Marking is gratefully acknowledged (http://www.uv-marking.eu/), grant agreement No 314630.Peer reviewe