Starting from a simple concept, transferring the shape of an interference pattern directly to the surface of a material, the method of Direct Laser Interference Patterning (DLIP) has been continuously developed in the last 20 years. From lamp-pumped to high power diode-pumped lasers, DLIP permits today for the achievement of impressive processing speeds even close to 1 m2/min. The objective: to improve the performance of surfaces by the use of periodically ordered micro- and nanostructures. This study describes 20 years of evolution of the DLIP method in Germany. From the structuring of thin metallic films to bulk materials using nano- and picosecond laser systems, going through different optical setups and industrial systems which have been recently developed. Several technological applications are discussed and summarized in this article including: surface micro-metallurgy, tribology, electrical connectors, biological interfaces, thin film organic solar cells and electrodes as well as decorative elements and safety features. In all cases, DLIP has not only shown to provide outstanding surface properties but also outstanding economic advantages compared to traditional methods.
Innovative surfaces are successful, if we succeed to put in the correct place the correct property with technological
efficiency. Until now, material surfaces can be systematically structured in different ways in order to fulfil chemical or
mechanical requirements such as corrosion protection or wear resistance for example. Moreover, the properties of
materials are strongly related to their microstructure as well as to their spatial distribution. For that reason, the design of
materials with tailored microstructures is a key for the functionalization of surfaces. This is possible by an artificial
fabrication technique called Laser Interference Metallurgy.
In this context, textured or functionalized surfaces are beneficial in overcoming stiction and adhesion in MEMS devices.
With regard to tribological applications, a systematic study of the effect of geometrically differing laser interference
patterns on the wetting behaviour of metallic gold thin films with a thickness of about 300 nm and 125 μm thick
polyimide foils should be presented. It could be shown that in case of gold films, a laser interference patterning
reinforces the hydrophilic sample behavior whereas the polyimide foils reveal a significant increase in hydrophobicity
after the laser patterning process. Both wetting regimes are advantageous under dry or lubricated friction conditions. The
corresponding geometrical limits of the abovementioned method concerning the structure depth, periodicity and pattern
form has been determined. All the samples have been characterized by scanning electron and focused ion beam
microscopy and white light interferometry. Additionally, IR spectroscopy has been applied to the polyimide samples in
order to separate topographic and chemical influences.
The physical and chemical behaviour of materials is strongly correlated with their microstructure. Therefore, much effort
is invested in the advanced microstructural design of metallic thin films.
Laser Interference Metallurgy (LIMET) is used to locally tune the grain architecture of metallic thin films from the nanoto
the microscale. This means a defined size and orientation of the grains with lateral periodicity, by interfering on the
sample surface two or more laser beams of a high power nanosecond pulsed Nd:YAG laser. This technique enables the
local nucleation and crystallization of amorphous or nanocrystalline metallic thin films, thus combining nano- and
microcrystalline regions ordered in periodic line- or lattice-like arrangements in a composite architecture.
After having locally modified the microstructure of e-beam evaporated Pt and Au thin films by laser irradiation a wet
chemical etching procedure was induced in hot aqua regia. Doing so, a selective etching is achieved without using
conventional lithography. Due to the laser-induced recrystallization in periodic structures, these microcrystalline zones
of specific oriented grains show a higher resistance against the wet chemical etchant than the as-deposited,
nanocrystalline areas, which are completely removed down to the substrate. Therefore, this procedure may have the
potential to be an alternative, low cost approach to conventional lithographic techniques and provides a novel method for
a straight-forward patterning of metallic thin films.
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