The increasing bacterial resistance to antibiotics is prompting research into new approaches to design bacterial repellent surfaces. This work investigated the hot embossing of sub-micron direct laser interference patterning (DLIP) and laser-induced periodic surface structures (LIPSS) textures from stainless steel onto polypropylene samples to achieve bacterial repellent properties. Staphylococcus aureus bacteria were adhered to the textured surfaces, and adhered bacterial counts were compared to untextured polypropylene using colony-forming unit and scanning electron microscopy analysis. Both DLIP and LIPSS textures, with a periodicity of around 700 nm, significantly reduced bacterial colonization compared to untextured samples. These findings highlight the potential of DLIP and LIPSS textures as effective strategies for developing antimicrobial polymer materials.

Increasing demands on the reproducibility and accuracy of lab-on-a-chip systems in the life science sector require new tools for the molding of polymer films with spatially selectively functionalized surfaces. By applying local micro- and nanostructuring to the molding tools, the aim is to achieve multifunctionality of the polymer films, by setting certain wetting properties. This means that fluid-affecting properties (hydrophobic, hydrophilic) should be possible. To functionalize polymer films, the replication tools were specifically microstructured using laser-based surface functionalization. The periodic micro- and nanostructures were produced with the help of nanosecond pulsed and picosecond pulsed laser systems using Direct Laser Interference Patterning. For this purpose, complex functional microstructures in the range of 0.1 mu m to 100 mu m were developed based on a bionic approach. The functional properties were transferred in a one-step replicative process using UV-imprinting and were subsequently verified by determining the wetting behavior of the molded microfluidic films and the corresponding laser microstructured replication tools. This publication presents the successfully developed processes and the promising results of this series of experiments. (c) 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the scientific committee of the CIRP BioM 2024

Surface roughness measurement is an integral part of the characterization of microtextured surfaces. Multiple established software packages offer the calculation of roughness parameters according to ISO 25178. However, these packages lack a specific set of features, which we hope to address in this work. Firstly, they often lack or have limited capabilities for automated and batch analysis, making it hard to integrate into other applications. Secondly, they are often proprietary and therefore restrict access to some potential users. Lastly, they lack some capabilities when it comes to the analysis of periodic microtextured surfaces. Namely, common parameters such as the peak-to-valley depth, spatial period and homogeneity cannot be calculated automatically. This work aims to address these challenges by introducing a novel Python library, Surfalize, which intends to fill in the gaps regarding this functionality. The functionality is described and the algorithms are validated against established software packages or manual measurements.

This study explores the enhancement of biocompatible titanium‐based implants through surface functionalization for improved bone healing. Specifically, a near‐beta type Ti‐13Nb‐13Zr alloy is 3D printed using laser powder bed fusion and subsequently textured using nanosecond (ns) and picosecond (ps) direct laser interference patterning (DLIP) to create single‐scale and multi‐scale surface textures. On these textures, the cell behavior, morphology, metabolic activity and osteogenic differentiation potential of human bone marrow stromal cells are assessed using fluorescence microscopy and MTS assays. Moreover, tissue non‐specific alkaline phosphatase activity served as an early osteoblast production marker. Compared to untextured specimens, both types of textures exhibited higher metabolic activity and cell proliferation. Single‐scale ns‐DLIP textures encouraged cell extensions anchored in groove regions, while ps‐DLIP textures with hierarchical structures promoted cell extensions attaching to nanostructures on sidewalls. The groove width and nanotopographies in groove areas facilitated cell spreading. Surface topography, roughness, and surface chemistry (surface energy, wettability) influenced cell adhesion, proliferation, and differentiation. A comprehensive evaluation of DLIP‐generated surface textures, including their topography and chemical states, complements the factors affecting in vitro cell behavior. Overall, this research demonstrates the potential of surface‐functionalized 3Dprinted titanium for a novel generation of biocompatible implants.

Internal combustion engines are increasingly regulated in regard to efficiency and environmental impact, which requires advanced optimization strategies of engine components. The contact between the top ring and the cylinder liner is critical to the efficiency of an internal combustion engine. As shown in a previous study, an amorphous carbon coating can greatly improve the friction properties of piston rings. This work expands on these results by fabricating laser‐interference‐induced microchannels on the coating perpendicular to the direction of movement with a mean depth of 0.97 and 3.13 μm spatial period to further optimize the tribology. Fired single‐cylinder engine measurements of the microtextured rings show a significant reduction in mean piston assembly friction of 5% for operation points that are relevant for urban transportation and up to 10% for specific operation points. Subsequent multibody elastohydrodynamic simulations prove that measured friction changes result from the compression ring microtexture. In particular, the microtexture increases the hydrodynamic pressure, reduces hydrodynamic losses, and leads to 20% lowered compression ring losses for an entire combustion cycle of the investigated operation point. In the future, such tribological concepts can be deployed in internal combustion engines that are powered by sustainable hydrogen or methanol.

Direct laser interference patterning (DLIP) is applied on additively manufactured near-beta Ti-13Nb-13Zr using nanosecond (ns) and picosecond (ps) pulses to tune its surface properties. Multiscale surface chemical and microstructural analyses (AES, XPS, XRD, SEM, TEM, GD-OES, contact angle) of those DLIP states are performed for understanding the corrosion behavior in a physiological PBS solution. Increased beta-phase fractions and uniformly thick passive layers of ns-DLIP surfaces led to enhanced corrosion stability compared to ps-DLIP with defective surface oxide. Both DLIP states control the surface wettability, thereby limiting corrosion and metal ion release rates, which is beneficial for implant applications.

With the increasing processing power of micro-electronic components and increasing spatial limitations, ensuring sufficient heat dissipation has become a crucial task. This work presents a microscopic approach to increasing the surface area through periodic surface structures. Microstructures with a periodic distance of 8.5 µm are fabricated via Direct Laser Interference Patterning (DLIP) on stainless steel plates with a nanosecond-pulsed infrared laser and are characterized by their developed interfacial area ratio. The optimal structuring parameters for increasing the surface area were investigated, reaching peak-to-valley depths up to 12.8 µm and increasing surface area by up to 394%. Heat dissipation in a natural convection environment was estimated by measuring the output voltage of a Peltier element mounted between a hot plate and a textured sample. The resulting increase in output voltage compared to an unstructured sample was correlated to the structure depth and developed interfacial area ratio, finding a maximum increase of 51.4%. Moreover, it was shown that the output voltage correlated well with the structure depth and surface area.

With rising prevalence of bone and skeletal diseases around the world, combatting implant failure through novel approaches has become a growing area of research. A novel way to produce tailored implants is additive manufacturing, which offers unprecedented design flexibility. On the other hand, the osseointegration of such implants can be optimized by applying periodic micro-textures on the surface, using laser-based techniques. In particular, the technique of Direct Laser Interference Pat-terning (DLIP) offers both high throughput and the possibility to produce structures with small feature sizes. In this work, DLIP is applied to produce line-like micro textures on additively manufactured Ti-13Nb-13Zr parts. Using different solid-state lasers, the effect of pulse durations in the nanosecond to femtosecond regime and laser wavelengths from the ultraviolet to near infrared spectrum on the micro texture topography is reported. For each wavelength and pulse duration, laser parameters are varied systematically. The surface topography of the specimens is characterized through scanning -electron microscopy, and surface roughness is measured with confocal microscopy. Interaction with nanosecond pulses is characterized by melting, resulting in mostly smooth textures, whereas picosec-ond and femtosecond pulses produce hierarchical textures with laser-induced periodic surface struc-tures.

Moving surface interactions between rigid and compliant materials have a wide range of functional applications in the automotive, aerospace and medical industries. This study investigates the cutting and frictional performance of textured stainless steel scalpel blades using polyurethane as the counterpart material. Groove textures of controlled geometries, oriented parallel and tangential to the primary cutting edge were produced using DLW and DLIP processes. Empirical investigations were conducted to study the influences of groove width, depth, separation distance and orientation on the performance of the textured blades under dry conditions.

Direct laser interference patterning (DLIP) employing sub-picosecond IR irradiation allows for the ultrafast processing of polyaniline surfaces polymerized onto a poly(methyl methacrylate) substrate (PANI@PMMA) achieving excellent quality features. The patterning shows high levels of precision regarding control of width and height in micro/nanoarrays, giving customization to the surfaces. The electroactive property evaluation suggests the conductivity presents anisotropic characteristics following the patterning of the polymeric surfaces (RSL = 54 +/- 5 kCI sq-1 and RST = 1.7 +/- 3 MCI sq-1, longitudinal and transversal resistance modes respectively). The evidence is supported by electrostatic force microscopy measurements. These results indicate potential applicability in the biomedical field of nerve and myocardial tissue regeneration.

Direct laser interference patterning (DLIP) has emerged as a versatile tool for producing well-defined microstructures that mimic natural surfaces with the aim of obtaining functionalized surfaces on relevant technological materials. On the other hand, the fabrication of surface patterns with micro- and submicron resolution features necessitates of advanced monitoring and setup strategies in order to ensure repeatability as well as quality control. In addition, the monitoring systems also allow inline capabilities to enable a closed-loop control approach. A possible strategy, that has been already applied to different laser processes, is the utilization of the sound pressure generated by the laser beam hitting the surface and producing ablation that can be detected and analyzed using commercially available microphones. In this frame, this work focuses on the analysis of the acoustic information extracted from the audio signal for determining process-inherent characteristics in DLIP, allowing the calculation of interference volume using stainless steel and titanium as reference materials. The results show that the acoustic emission measured at the ablation spot can be correlated to the interference volume shape and thus allowing to approximate the size of the interference spot. The possible utilization of this approach as an auto-focus and auto-setup method during DLIP is discussed.

Additive manufacturing of near β-type Ti-13Nb-13Zr alloys using the laser powder bed fusion process (LPBF) opens up new avenues to tailor the microstructure and subsequent macro-scale properties that aids in developing new generation patient-specific, load-bearing orthopedic implants. In this work, we investigate a wide range of LPBF parameter space to optimize the volumetric energy density, surface characteristics and melt track widths to achieve a stable process and part density of greater than 99 %. Further, optimized sample states were achieved via thermal post-processing using standard capability aging, super-transus (900 °C) and sub-transus (660 °C) heat treatment strategies with varying quenching mediums (air, water and ice). The applied heat treatment strategies induce various fractions of α, martensite (α', α'') in combination with the β phase and strongly correlated with the observed enhanced mechanical properties and a relatively low elastic modulus. In summary, our work highlights a practical strategy for optimizing the mechanical and corrosion properties of a LPBF produced near β-type Ti-13Nb-13Zr alloy via careful evaluation of processing and post-processing steps and the interrelation to the corresponding microstructures. Corrosion studies revealed excellent corrosion resistances of the heat-treated LPBF samples comparable to wrought Ti-13Nb-13Zr alloys.

Medical implants, such as dental screws or hip stems, are made of biocompatible materials so that they can be well integrated into living organisms. For instance, titanium and its alloys offer high biocompatibility and osseointegration, making these materials very common in such applications. Furthermore, the new advancements in additive manufacturing allow to customize the fabrication of implants which are tailored to the patients’ individual needs. Furthermore, it is known that the structural elements with feature sizes in the micrometer range on the implants’ surface play a significant role in the attachment and proliferation of cells. These elements can be fabricated through laser-based texturing methods that offer high flexibility and high throughput. In this work, we explore the potential of fabricating surface microstructures on additive manufactured near-beta titanium alloy parts (Ti-13Nb-13Zr), using the Direct Laser Interference Patterning (DLIP) technique. Hereby, a single laser beam is split into two sub-beams that are subsequently recombined on the substrate surface where they form a line-like interference pattern with a defined spatial period. We combine DLIP with a picosecond-pulsed laser source and investigate the morphologies and surface features that can be created. Thereby, different laser wavelengths were employed, including 355 nm, 532 nm and 1064 nm. The resulting surface textures are analyzed using scanning electron microscopy (SEM) and confocal microscopy (CM), showing different types of laserinduced periodic surface structures (LIPSS), of which the geometry and size depended on the used process parameters.

Complex repetitive periodic surface patterns were produced on a near-beta Ti-13Nb-13Zr alloy, using two-beam Direct Laser Interference Patterning (DLIP) employing a picosecond-pulsed laser source with wavelengths of 355 nm, 532 nm and 1064 nm. Different types of Laser-induced periodic surface structures (LIPSS) are produced, including low and high spatial frequency LIPSS, which are observed frequently on top of the line-like DLIP microstructures, as well as quasi-periodic microstructures with periods greater than the laser wavelength. The feature size of the fabricated LIPSS features could be tuned as function of the utilized laser process parameters.

An increase in the angular spread of incident light was obtained in FTO thin films after the generation of periodic micro- and nano-structures with infrared sub-picosecond Direct Laser Interference Patterning.

Microtextures generated by pulsed lasers allow for changing the surface properties of a wide palette of materials by replicating nature's most effective topographies. In the case of laser-induced microtextures, the surface's wetting properties evolve over time and eventually stabilize. The size of the fabricated features and the initial surface roughness strongly influence this transition and play a key role in the determination of the final wetting state. This work aims to study the wettability of textured stainless-steel with two different surface finishes. Nanosecond Direct Laser Interference Patterning was applied to fabricate a wide range of dot-like microtextures that were evaluated in terms of surface roughness. The water contact angle was monitored for up to 90 days, showing a transition from hydrophilic to hydrophobic. Applying the Wenzel model, the wettability transition was analyzed in regard to surface roughness, and the transition of the average Young contact angle could be extrapolated. In the steady-state, the textured surfaces exhibited the rose-petal effect, where contact angles up to 154.4 were attributed to the microtextures, while a simultaneous high drop adhesion could be related to the initial surface finish. Measurements with water and diiodomethane showed that the textures were both hydro-phobic and oleophilic in the steady-state. The surface free energy was estimated and decreased on all textures compared to the untextured reference.

Forward facing aerodynamic surfaces such as rotors and wings are susceptible to ice build‐up when exposed to atmospheric icing conditions. If not removed, accumulated ice on aircraft surfaces affects aerodynamics or rotation balance, which can ultimately lead to increased fuel consumption, reduced operational performance and to potentially hazardous situations. Laser surface structuring is proposed as an alternative technology to coatings for achieving icephobic properties and support anti‐icing and de‐icing processes on aerodynamic surfaces. However, to authors’ knowledge, no study available in the literature reports on the icing behavior of microtextured curved aerodynamic profiles and the effect of the laser surface treatment on the electrothermal heating used for ice protection systems. In this work, direct laser interference patterning is employed to fabricate hierarchical micro‐ and nanostructures directly on a non‐planar titanium airfoil. The anti‐icing performance of the laser‐treated airfoil is tested in an icing wind tunnel under simulated atmospheric conditions. The results demonstrate a self‐limiting ice growth, a decrease in the deicing electro‐thermal power up to 80%, and up 60% lower heating power necessary to keep the surface free of ice than on the reference airfoil.

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.