The use of pulsed laser irradiation techniques has proven to be a clearly effective procedure for the achievement of surface properties modification via micro-/nano-structuration, different conceptual approaches having been the subject of research and extensively reported in the literature. Beyond the broad spectrum of applications developed for the generation of structured surfaces of metallic materials with specific contact, friction and wear functionalities, the application of laser sources to the surface structuration of metal surfaces for the modification of their wettability and corrosion resistance properties is considered. Multi-scaled hierarchical surface microstructures fabricated on characteristic alloys (the concrete case of Ti6Al4V alloy is considered as example) by the combination of two complementary laser micro/nano-structuring techniques (Direct Laser Writing and Direct Laser Interference Patterning) are reported. Static contact angle measurements show a clearly hydrophobicity enhancement for both types of processing options and a clear improvement on the corrosion resistance of patterned samples of either type is observed. A discussion of the reported features in view of the applicability of the technique to industrial-scope problems is provided.
Recently, product protection and tracking became increasingly important due to the spread of piracy and counterfeiting. A common anti-counterfeiting procedure is embedding holographic motives or logos onto the good. If the motive is engraved directly onto the material surface, these features are inseparable from the good adding a higher degree of security. Holographic coloring is achieved by fabricating periodic surface structures, where the dimensions of the spatial periods lie in the order of the wavelengths contained in the visible spectrum. However, the fabrication of such periodic features directly on the product surface at high resolution and manufacturing speed is still challenging. Direct Laser Interference Patterning (DLIP) is an industrial compatible method with high processing flexibility which allows the structuring of holographic motives with high resolution and throughput. In this work, DLIP is employed to produce diffraction gratings with variable spatial periods and feature heights on a transparent PET substrate, which is a polymer commonly used for mass consumer goods and packaging. A numerical model based on the finite element method was used to restrict the gratings’ geometrical parameters that maximize the diffraction efficiency in reflection mode before their fabrication. Then, using the design of experiment approach, the laser processing parameters (laser power, pulse-overlap, spatial period) were selected in order to maximize the experimental first-order diffraction intensity, measured with a photospectrometer. The results allow to find the optimum set of parameters to fabricate homogeneous gratings with a first-order reflected intensity up to 4 % of the light source intensity.
This study describes the fabrication of dot and line-like periodic surface structures on metals, using new developed optical configurations based on Direct Laser Interference Patterning (DLIP). The optical setups are optimized for high throughput processing, for instance by shaping the beam profiles to elongated rectangular laser spots (with approximately 5.0 mm x 0.1 mm size) or by combining the DLIP optics with a scanner system. Later, aluminum and stainless steel substrates are processed using a nanosecond and picosecond pulsed laser source delivering up to 13 W and 180 W of laser power for the 10 ps and 10 ns systems, respectively. Depending on the pulse repetition rate applied and the pulse duration, a significant heating of the substrate volume was observed for the ns pulses. In this way, driven by Marangoni convection mechanisms, structures with exceptionally high aspect ratios could be produced. In case of the structures processed with ps pulses, large areas showing high pattern homogeneity were fabricated. Finally, water contact angle measurements of the produced structures are used to demonstrate the capability to control the surface wettability of the metals, even reaching super-hydrophobic conditions (using deionized water at room temperature). Also, the ability of the textured surface for increasing the freezing time of water droplets, and thus reducing ice-formation, is demonstrated at -20°C. Finally, the applicability of the DLIP scanner technology for decorative applications is shown. The characterization of the treated and untreated surfaces was performed using scanning optical microscopy and white light interferometry.
Surfaces with well-defined features (e.g. periodic structures) have shown to exhibit outstanding properties. The design of these textured surfaces often follows a biomimetic approach motivated by living organisms which developed over time through natural selection and evolution. The efficient production of these versatile patterns still represents one of the greatest technical challenges today in the development of new customized surface functionalities. Direct Laser Interference Patterning (DLIP) has been identified as an outstanding technology for the efficient fabrication of tailored surface structures. This method can show impressive processing speeds (up to 1 m²/min) as well as a superior flexibility in producing extremely versatile surface structures. This work gives an overview about recent developments of the DLIP technology by focusing on the topics: structure flexibility, process productivity, technical implementations and recent examples of achieved surface functionalities.
Periodic surface structures with micrometer or submicrometer resolution produced on surfaces of different technological parts can be used to improve their mechanical, biological or optical characteristics. While direct laser interference patterning (DLIP) already permits structuring speeds of up to 0.9 m2/min under constant process parameters, fabrication of individualized surface structures fabricated "on-the-fly" is not possible at high speeds. In this study, a scanner-based DLIP optical head is presented which combines the flexibility of the DLIP technology with a high-performance galvanometer scanner system. An evaluation of the structuring results as well as various application examples will be presented.
It is well known that micro and sub-micrometer periodical structures play a significant role on the properties of a surface. Ranging from friction reduction to the bacterial adhesion control, the modification of the material surface is the key for improving the performance of a device or even creating a completely new function. Among different laser processing techniques, Direct Laser Interference Patterning (DLIP) relies on the local surface modification process induced when two or more beams interfere and produce periodic surface structures. Although the produced features have controllable pitch and geometry, identical experimental conditions applied to different polymers can result on totally different topologies. In this frame, observations from pigmented and transparent polycarbonate treated with ultraviolet (263 nm) and infrared (1053 nm) laser radiation permitted to identify different phenomena related with the optical and chemical properties of the polymers. As a result from the experimental data analysis, a set of material-dependent constants can be obtained and both profile and surface simulations can be retrieved, reproducing the material surface topography after the surface patterning process.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print format on
SPIE.org.