Direct Laser Interference Lithography Research Articles

Superhydrophobic Antifrosting 7075 Aluminum Alloy Surface with Stable Cassie-Baxter State Fabricated through Direct Laser Interference Lithography and Hydrothermal Treatment.

Frost formation and accumulation can have catastrophic effects on a wide range of industrial activities. Hence, a dual-scale surface with a stable Cassie-Baxter state is developed to mitigate the frosting problem by utilizing direct laser interference lithography assisted with hydrothermal treatment. The high Laplace pressure tolerance under the evaporation stimulus and prolonged Cassie-Baxter state maintenance under the condensation stimulus demonstrate the stable Cassie-Baxter state. The dual-scale surface exhibits a lengthy frost-delaying time of up to 5277 s at -7 °C due to the stable Cassie-Baxter state. The self-removal of frost is achieved by promoting the mobility of frost melts driven by the released interfacial energy. In addition, the dense flocculent frost layer is observed on the single-scale micro surface, whereas the sparse pearl-shaped frost layer with many voids is obtained on the dual-scale surface. This work will aid in understanding the frosting process on various-scale superhydrophobic surfaces and in the design of antifrosting surfaces.

Fabrication of periodic hierarchical structures with anti-icing performance by direct laser interference lithography and hydrothermal treatment

Ice accumulation could result in a massive economic burden as well as major life safety issues. Because of their immense potential to ease icing problems, superhydrophobic structures have captured the curiosity of many researchers. Herein, the periodic hierarchical porous structures that have outstanding anti-icing performance were created using two-beam direct laser interference lithography and hydrothermal treatment. The periodic hierarchical porous structures were composed of periodic micro ridge arrays covered with interlaced grown standing nanoflakes. The high-water repellency of the periodic hierarchical porous structures was characterized by the high contact angle and the low rolling angle of 163.7° ± 1.5° and 3.4° ± 0.8°, respectively. The high-water repellency of the periodic hierarchical porous structures exhibits a long-term stability in air and durability in contact with water. The experimental results indicated that the anti-icing performance of the periodic hierarchical porous structures was achieved through the long-term inhibition of ice nucleation and low ice adhesion strength. The ice nucleation inhibition time could reach up to 378 s, which was more than 11.8 times longer than the untreated surface. The ice adhesion strength could be reduced to 48.3 kPa, which was more than 6.3 times lower than the untreated surface. The proposed manufacturing strategy and designed structures could be useful for designing anti-icing structures.

Laser interference additive manufacturing ordered Cu microstructure

Here, we explored a novel additive manufacturing method on microscale for metal, carrying out direct laser interference lithography technique under the liquid phase. 3D ordered Cu microstructures with a spatial period of 12 μm could be obtained by this method using the nanosecond laser at the wavelength of 1064 nm with a pulse duration of 5–8 ns. Therefore, the phenomenon of the molten interconnected between Cu2O particles become obvious gradually with the increase of the laser fluence. Furthermore, the height of the microstructure can be tuned by pulse number at the constant laser fluence, which was confirmed by optical microscopy. Finally, the effective method is represented for the additive manufacturing of 3D ordered metal microstructure, which can avoid the environmental pollution by metal microparticles.

Slippery liquid infused porous surfaces with anti-icing performance fabricated by direct laser interference lithography

Slippery liquid-infused porous surfaces (SLIPSs) have recently been an effective alternative to superhydrophobic surfaces (SHSs) for anti-/de-icing applications. However, in practical applications, SLIPSs are limited by their unsatisfactory substrate manufacturing technologies and unsustainable oil storage and adjustment capacities. In this work, we fabricated micro-groove structures on SLIPS substrates by direct laser interference lithography (DLIL) in one step, coating with lubricant oil to obtain DLIL-SLIPS. The oil was firmly locked and stored into the groove structures, which can be self-supplemented even after 10 icing/de-icing cycles, leading to an efficient anti-icing performance as well as improved durability and robustness. Experiments showed that the DLIL-SLIPS exhibits better ice adhesion property with the apparent contact angle (CA) of 143° and ice adhesion strength of 7.16 kPa. The coefficient of friction was reduced up to 63.3 % compared to the substrate. They indicated that the groove structures have the excellent function of friction-reduction. We envision that this method is useful for the fabrication of composite functional SLIPS in anti-icing and friction-reduction applications such as bearings and turbine blades, especially in extreme environments.

Interdisciplinary Methods for Zoonotic Tissue Acellularization for Natural Heart Valve Substitute of Biomimetic Materials.

The goal of this work was to create a bioactive tissue-based scaffold using multi-disciplinary engineering materials and tissue engineering techniques. Materials & methods: Physical techniques such as direct laser interference lithography and proton radiation were selected as alternative methods of enzymatic and chemical decellularization to remove cells from a tissue without degradation of the extracellular matrix nor its protein structure. This study was an attempt to prepare a functional scaffold for cell culture from tissue of animal origin using new physical methods that have not been considered before. The work was carried out under full control of the histological and molecular analysis. Results & conclusions: The most important finding was that the physical methods used to obtain the decellularized tissue scaffold differed in the efficiency of cell removal from the tissue in favour of the laser method. Both the laser method and the proton method exhibited a destructive effect on tissue structure and the genetic material in cell nuclei. This effect was visible on histology images as blurred areas within the cell nucleus. The finite element 3D simulation of decellularization process of the three-layer tissue of animal origin sample reflected well the mechanical response of tissue described by hyperelastic material models and provided results comparable to the experimental ones.

The distribution of O and N in the surface region of laser-patterned titanium revealed by atom probe tomography

Direct Laser Interference Lithography (DLIL) has shown to be a promising technique to chemically and physically alter the surface of titanium. In this work, atom probe tomography analysis was performed on DLIL-treated titanium to obtain the chemical composition of the surface in maxima and minima interference positions. The analysis revealed that a multilayer structure consisting of oxide/oxynitride is formed at both positions; however, the chemical composition is altered differently between the two. The observed difference is believed to be due to an uneven heating and temperature distribution, which is demonstrated by thermal simulations.

Corrosion behavior of titanium modified by direct laser interference lithography

This paper reports on the corrosion behavior of Titanium Grade 2 when subjected to non-contact laser functionalization. Direct Laser Interference Lithography (DLIL) was used to create periodic topography with two different surface patterns on pre-modified titanium. Corrosion resistance was measured in physiological saline at 37 °C. Electrochemical Impedance Spectroscopy data (EIS) and potentiodynamic polarization curves were correlated with the characteristics of the passive films through analysis of the topography, chemical composition, and thickness of oxides formed on the titanium after surface modifications. The corrosion tests showed that laser-textured surfaces have a beneficial impact on titanium corrosion resistance in a physiological saline solution 0.9% NaCl. Moreover, the passive layer on DLIL-modified samples is more stable and less susceptible to growth in the corrosive environment. The results highlight the local interaction of DLIL treatment of the titanium surface after it had been shot-peened and acid-etched. The improved corrosion resistance in DLIL samples derives mainly from changes in the surface topography, chemical composition, and thickness of oxide films obtained after laser processing.

Fabrication of biomimetic superhydrophobic and anti-icing Ti6Al4V alloy surfaces by direct laser interference lithography and hydrothermal treatment

Nature gives us a large number of inspirations in designing functional materials. Many plant leaves with self-cleaning properties are ubiquitous in nature. These plants have hierarchical structures, which have extreme repellency to liquids and have considerable technical potential in various applications. Herein, we present a method for fabricating bionic taro leaf surfaces by direct laser interference lithography (DLIL) and hydrothermal treatment. The micro-pillar array structure (MPA) was fabricated by DLIL, and a layer of nano-grass structure (NG) was grown on it by hydrothermal treatment. Experiments indicate that the hierarchical composite structures not only have a satisfactory superhydrophobic function with the apparent contact angle (CA) of 172° and sliding angle (SA) of 4°, but also have a strong anti-icing ability with the delay time (DT) of 3723 s. The method is simple and high-efficient for fabricating bionic self-cleaning and anti-icing surfaces.

Effect of laser functionalization of titanium on bioactivity and biological response

This study proposes Direct Laser Interference Lithography as a highly suitable technique for functionalization titanium surfaces for biomedical applications. DLIL was employed to produce periodic patterns on titanium after two commonly used surface treatments of implantable devices (shot peening and acid etching). The biomedical potential of the proposed method was analyzed using immersion tests in a simulated body fluid solution and cell adhesion tests. After 48 h of immersion surface morphology, the chemical composition and phase structure of the apatite layers deposited on the modified titanium were analyzed. In order to analyze the kinetics of the apatite layer growth, X-Ray Photoelectron Spectroscopy measurements at different soaking times were performed. Cell adhesion tests were performed using human fetal osteoblastic cells (hFOB). The adhered cells were analyzed using confocal and scanning electron microscopies after 48 h of incubation. The formation of biomimetic apatite layers was accelerated on the titanium surface structures after DLIL modification. The periodic titanium patterns induced more uniform and direct cell growth. This effect is mainly connected with the surface properties of the DLIL-modified substrates. The formation mechanism of biomimetic apatite on the textured titanium samples, as well as the compounds created on the surface, are discussed.

A Fundamental Study of a Surface Modification on Silicon Wafer Using Direct Laser Interference Patterning with 355-nm UV Laser

The growing need for precision machining, which is difficult to achieve using conventional mechanical machining techniques, has fueled interest in laser patterning. Ultraviolet (UV) pulsed-lasers have been used in various applications, including the micro machining of polymers and metals. In this study, we investigated direct laser interference patterning of a silicon waver using a third-harmonic diode-pumped solid-state UV laser with a wavelength of 355 nm. Direct laser lithography is much more simple process compare to other submicro processing method. We have studied interference patterning for silicon wafers as a basic research for direct laser interference patterning on wafer surfaces without mask. And Finite element analysis (FEA) was performed for a 150° biprism using modeling software (COMSOL Multiphysics 5.4) to determine changes in the periodic patterns according to the focusing distance in the direct interference lithography experiment. In further study, we expect this technique to be applied to direct laser interference lithography on metals.

Fabrication and transfer printing of periodic Pt nanonetwork gratings

Metal nanonetworks are applied in various applications, such as biomedicine, bionic materials, optical materials, and new energy materials. Here, periodic variable-sized Pt nanonetwork gratings (PtNGs) are fabricated on the surface of a Pt/Si substrate with single pulse two-beam direct laser interference lithography. The fabricated PtNGs are transferred onto the surface of a glass substrate with polymethyl methacrylate as the transfer mediator. Exposure with different film thicknesses, contrasts, and intensity distributions of the laser interference spot is analyzed, and the formation of nanopatterns is explained. Results show that with the change in the thicknesses of the Pt film, the exposed structures present Pt nanoparticles (PtNPs), Pt gratings, and PtNGs. The morphology and the feature size of the PtNGs are influenced by intensity distributions and the contrast of the laser interference spot significantly.

Microstructure and mechanical properties of titanium subjected to direct laser interference lithography

This study concerns a detailed cross-section microstructural analysis conducted by combining complementary methods such as FIB, SEM, EDS and STEM on different scales in order to elucidate the impact of direct laser interference lithography on the microstructure and surface chemistry of a Ti substrate after laser patterning. Special attention was paid to correlate the mechanical properties determined by the nanoindentation tests with the microstructure and phase composition analysed using GI-XRD. Direct laser interference lithography surface texturing results in the formation of a thin (1–1.5 μm), continuous layer with lath-like grains. The GI-XRD analysis showed no changes in phase composition, which is in agreement with our previous results. Furthermore, laser patterning led to an increase in the nano-hardness of the surface (from 2.8 GPa to 6.6 GPa) that is mainly related to the changes that took place in the microstructure. The results presented are important to an evaluation of laser-patterned surfaces in biomedical applications, as their ultimate use depends not only on topographical changes but also mechanical properties variations as well as microstructure evolution which affects its electrochemical properties.

Fabrication of oil-water separation stainless steel mesh via direct laser interference lithography, candle soot deposition, and thermal treatment

In this work, the authors propose a method to obtain micro- and nano-structures on the stainless steel mesh (SSM), which showed the potential application for the treatment of water pollution based on its hydrophobicity and oleophilicity. The textured surfaces with the micrometer scale pore array patterns on the SSM are formed by three-beam laser interference lithography. And the nanostructures, such as nanorods, nanowires, and nanoflakes, are obtained on the surfaces of the SSMs after laser irradiation by heating for 70 min at approximately 600 °C under ambient conditions. The results showed that the nanostructures can be easier to grow on the rough surface than the smooth ones. In addition, these nanostructures are also grown on the surfaces of the laser irradiated SSM with the candle soot (LISSM@C). Raman spectrum proves that the nanostructures are α-Fe2O3 and α-Fe2O3/reduced graphene oxide (rGO). The measurement of the contact angle indicates that the oil-water separation can be realized on the LISSM@C after the thermal treatment.

Influence of surface pattern on the biological properties of Ti grade 2

This paper presents a detailed characterization of Ti surface geometries as produced by non-contact laser functionalization and its impact on the process of protein adsorption. The proposed surface modification is designed for the local treatment of implantable devices with original roughness. In this work, titanium plates were initially modified by the two most common mechano-chemical treatments, shot peening and acid etching. The material under study was next functionalized DLIL (Direct Laser Interference Lithography) in order to obtained two different surface patterns: grooves and islands. The modified surfaces were characterized in terms of their shape, roughness, wettability, surface energy and chemical composition. For this purpose, the following methods were used: scanning electron microscopy, optical profilometry, atomic force microscopy, contact angle measurements, and X-ray photoelectron spectroscopy. Protein adsorption tests were conducted to consider the potential of the proposed methodology in biomedical applications and to compare the influence of the two different surface patterns on the initial state of ossointegration. To this end, XPS and FTIR studies were conducted. The systematic analysis presented will be useful when selecting an appropriate surface geometry for the local surface functionalization of implantable devices.

The fabrication of hydrophilic structure on lens via direct laser interference lithography

The temperature difference between indoor and outdoor could cause the formation of droplet on lens. A kind of new fog-proof technology is presented in this paper. Hydrophilic structures are patterned on the surface of lens by means of direct laser interference lithography. The contact angle (CA) and the morphology of the structure are observed under CA meter and optical microscope respectively. The results show that with the power of 49.1W, the incident angle of 9°, and the exposure times of 2, the structure with period of 30.7μm could be produced on the surface. What’s more, the CA meter shows that the produced structure could change the CA from 78° which is intrinsic to 58°.

Fabrication of hydrophobic structures on coronary stent surface based on direct three-beam laser interference lithography

To solve the problems with coronary stent implantation, coronary artery stent surface was directly modified by three-beam laser interference lithography through imitating the water-repellent surface of lotus leaf, and uniform micro-nano structures with the controllable period were fabricated. The morphological properties and contact angle (CA) of the microstructure were measured by scanning electron microscope (SEM) and CA system. The water repellency of stent was also evaluated by the contact and then separation between the water drop and the stent. The results show that the close-packed concave structure with the period of about 12 μm can be fabricated on the stent surface with special parameters (incident angle of 3°, laser energy density of 2.2 J·cm−2 and exposure time of 80 s) by using the three-beam laser at 1 064 nm, and the structure has good water repellency with CA of 120°.

Fabrication of hydrophobic structures on stent by direct three-beam laser interference lithography

Coronary heart disease has become one of the important causes of human death, and the current clinical treatment has a high long-term restenosis rate and is easy to form late stent thrombosis. In order to solve these problems, coronary artery stent surface was directly modified by laser interference lithography and the highly ordered concave structures were fabricated. The morphology and contact angle (CA) of the microstructure were measured with scanning electron microscopy and CA system. The water repellent property of the stent was also evaluated by the method of contacting the water drop with the stent and then separating. The results show that the close-packed concave structure with the period of about 12μm can be fabricated on the stent surface under special parameters (laser energy density of 3Jcm−2, incident angles of 2.8°, exposure time of 60s) by the three-beam laser interference of 1064nm and the form structure has good water repellency with contact angle of 120°.

Selected laser methods for surface structuring of biocompatible diamond-like carbon layers

Laser based surface structuring methods are among the fastest growing techniques and displace other surface treatments for applications such as marking, change of topography and microstructure. Such changes may lead to controlled modification of material properties, including their biocompatibility. The paper presents two laser techniques — picosecond Direct Laser Writing (DLW) and multi-beam Direct Laser Interference Lithography (DLIL). The purpose of the research was to create different shapes and dimensions of 2D and 3D periodical microstructures on the surface of thin diamond like carbon (DLC) coatings on different substrates. Resulting structures were further tested to find the influence of laser processing on the interaction of created scaffolds with the living cells in the direction of improvement of their directional growth and adhesion. The use of two different patterning methods (DLW and DLIL) allowed creation of structures with periods ranging between sub-microns to tens of microns, with different pattern resolutions, shapes (linear, dotted, crossed, hierarchical) and depths. Preliminary analyses have shown the possibility of high degree of control and improvement in the directional growth of smooth muscle cells and the proliferation of the endothelial cells, cultivated on migration channels created at DLC layers.

Fabrication of moth-eye structures on silicon by direct six-beam laser interference lithography

This paper presents a new method for the generation of cross-scale laser interference patterns and the fabrication of moth-eye structures on silicon. In the method, moth-eye structures were produced on a surface of silicon wafer using direct six-beam laser interference lithography to improve the antireflection performance of the material surface. The periodic dot arrays of the moth-eye structures were formed due to the ablation of the irradiance distribution of interference patterns on the wafer surface. The shape, size, and distribution of the moth-eye structures can be adjusted by controlling the wavelength, incidence angles, and exposure doses in a direct six-beam laser interference lithography setup. The theoretical and experimental results have shown that direct six-beam laser interference lithography can provide a way to fabricate cross-scale moth-eye structures for antireflection applications.

Superhydrophobic dual micro- and nanostructures fabricated by direct laser interference lithography

A method for the fabrication of highly ordered superhydrophobic dual micro- and nanostructures on silicon by direct laser interference lithography (LIL) is presented. The method offers its innovation that the superhydrophobic dual micro- and nanostructures can be fabricated directly by controlling the process of four-beam laser interference and the use of hydrofluoric acid (HF) to wipe off the silica generated during the process. Different laser fluences, exposure durations, and cleanout times have been investigated to obtain the optimum value of the contact angle (CA). The superhydrophobic surface with the CA of 153.2 deg was achieved after exposure of 60 s and immersion in HF with a concentration of 5% for 3 min. Compared with other approaches, it is a facile and efficient method with its significant feature for the macroscale fabrication of highly ordered superhydrophobic dual micro- and nanostructures on silicon.