Laser Processing Technology Research Articles

Femtosecond laser-textured superhydrophilic coral-like structures spread AgNWs enable strong thermal camouflage and anti-counterfeiting

Modulating the thermal emission of a material in the infrared (IR) range can be essential for various practical applications such as smart textiles, camouflage, and anti-counterfeiting. Although many different materials or structures have been proposed, the complex manufacturing processes are still hindering their widespread use. Herein, a facile femtosecond laser processing technology and a drop-coating method are introduced to form a patternable low emissivity film. Laser-treated polyimide films resulted in superhydrophilic structured surfaces that are uniformly coated with silver-nanowires (AgNWs) in aqueous solutions for low emissivity surfaces. Furthermore, the emissivity of the samples is as low as ∼0.2 without deterioration over 800 bending-releasing cycles. The as-prepared films also display good thermal camouflage properties, namely, the films reduced the thermal radiation temperature of an object by 35.8 °C when the object temperature was ∼69.1 °C. Additionally, this IR camouflage effect of the AgNWs coated samples shows excellent stability even in harsh environments such as immersion in water, acid, alkali, and salt solution and applied voltage. We also show that information encryption was possible by adjusting the amount of AgNWs. The design of this programmable patterned low emissivity film indicates an idea for the thermal camouflage and anti-counterfeiting technology, which can carry more abundant application scenario and disguise them more complex and sophisticated.

A Method for Preparing Surface Sub-Microstructures on Sapphire Surfaces Using Femtosecond Laser Processing Technology

Femtosecond laser processing technology is an advanced sub-micro-processing technique that enables the non-contact processing of various materials. This technology can be used to apply sub-micro structures for purposes such as hydrophilicity enhancement, optical transmittance improvement, and photonics detection. However, when it comes to processing micro/nanostructures on highly brittle materials using femtosecond lasers, there are challenges such as low processing efficiency, generation of debris, and microcracking. In this paper, we propose a method called the out-of-focus femtosecond laser direct writing technique combined with wet etching. This method offers simplicity, speed, and flexibility in preparing dense, large-area sub-microstructured surfaces on the brittle material sapphire. Our detailed investigation focuses on the impact of laser processing parameters (direct writing period, distance of focusing, direct writing speed, etc.) on the sub-microstructures of Al2O3 surfaces. The results demonstrate that this method successfully creates embedded sub-microstructures on the sapphire surface. The microholes, with a diameter of approximately 2.0 μm, contain sub-micro structures with a minimum width of 250 ± 20 nm. Additionally, we conducted experiments to assess the optical transmittance of sapphire nanostructures in the range of 350–1200 nm, which exhibited an average transmittance of approximately 77.0%. The water contact angle (CA) test yielded a result of 52 ± 2°, indicating an enhancement in the hydrophilicity of the sapphire nanostructures with only a slight reduction in optical transmittance. Our efficient fabrication of sub-microstructures on the sapphire surface of highly brittle materials offers a promising method for the production and application of brittle materials in the field of micro-optics.

Material dependent influence of ring/spot beam profiles in laser powder bed fusion

In recent years, the topic of beam shaping for improved laser material processing has rapidly grown influencing metal laser powder bed fusion (PBF-LB/M). Given the need to reduce the cost and improve control of the PBF-LB/M process to make it more competitive with traditional manufacturing methods, increasing productivity of PBF-LB/M is critical. When research reports a new beam profile (e.g. ring profile) to improve productivity on a specific material, it is often generalised, and assumed to have the capability to improve productivity in PBF-LB/M across the board. In this work, we use both low-fidelity simulations and experimental work to investigate the difference between Gaussian and ring/spot beam profiles on metals with very different thermal properties (a stainless steel and an aluminium alloy). We show that the two materials have opposite responses to the change in beam profile (both in terms of melt pool dimensions and thermal gradients); further, the most beneficial intensity distribution is dependent on the energy input to the material. This exemplifies yet another way in which the PBF-LB/M process is non-linear and contradicts the idea that a ring/spot laser profile is beneficial for all laser processing technologies. This highlights the need for further research into the non-linear effect of varying intensity distributions on laser processing before the benefits of dynamic beam shaping can be truly realised.

Femtosecond Laser Microfabrication of Artificial Compound Eyes

Over millions of years of evolution, arthropods have intricately developed and fine-tuned their highly sophisticated compound eye visual systems, serving as a valuable source of inspiration for human emulation and tracking. Femtosecond laser processing technology has attracted attention for its excellent precision, programmable design capabilities, and advanced three-dimensional processing characteristics, especially in the production of artificial bionic compound eye structures, showing unparalleled advantages. This comprehensive review initiates with a succinct introduction to the operational principles of biological compound eyes, providing essential context for the design of biomimetic counterparts. It subsequently offers a concise overview of crucial manufacturing methods for biomimetic compound eye structures. In addition, the application of femtosecond laser technology in the production of biomimetic compound eyes is also briefly introduced. The review concludes by highlighting the current challenges and presenting a forward-looking perspective on the future of this evolving field.

Controllable Fabrication of Organic Semiconductors for Aligned Microlasers and Integrated Photodetectors

AbstractEngineering of organic single crystal toward controllable and aligned patterns at microscale is crucial to the realization of highly integrated organic photonic devices and optoelectronics. However, precise positioning and controllable morphology of crystal structures is still challenging due to the strict conditions for crystal growth. In this paper, a solution based crystal regulation strategy with the assistance of template‐constrained growth method and femtosecond laser processing technology is developed to prepare aligned crystalline microribbon arrays. Simple solvent evaporation results in the random distribution and orientation of self‐assembled crystalline microribbons while it tends to form highly crystalline and orderly microribbon arrays assisted by the confined template microchannels. The large‐scale microribbon array can be fabricated as organic photodetectors with sensitive and fast response under 405 nm illumination. By virtue of the femtosecond laser processing technique, the microribbon arrays are precisely processed into a series of crystal subunits and each microribbon subunit can function as an individual microcavity resonator to produce stable, high‐quality organic laser. The facile solution based template‐constrained self‐assembly and femtosecond laser processing method provide novel strategies to generate highly oriented and controllable crystal structures for the potential applications in integrated organic lasers and optoelectronics.

Fabrication of polycrystalline LaB6 tips array by femtosecond laser and its field emission performance

Femtosecond laser processing technology has been used to achieve controlled processing of microtips array on the surface of polycrystalline LaB6 blocks. Under the condition of ensuring the integrity of the geometric morphology of the tips array, the tips with a height of 10 μm and a radius of curvature of 1 μm can be processed. The distribution of tips in the array is uniform, the morphology is complete, the crystal structure and physical phase of LaB6 have not changed after processing, which breaks through the technical problems of difficult processing and poor geometry consistency about polycrystalline rare-earth hexaboride tips emitter, and the processing area is no longer limited by the small size of single crystals. The field emission performance test indicated that the turn-on electric field is 2.8 V/μm, and the current density is 467.9 mA/cm2 when the applied electric field reached 9.4 V/μm.

Principal Analysis and Application of Laser Technology in Integrated Circuits

Since the constant development of science and technology and the popularization of electronic devices, integrated circuits are also developing in the direction of large scale and high precision. This requires the processing of integrated circuits to be constantly refined. This also prompted the laser technology has become an important processing technology in the manufacturing process of large-scale integrated circuits. Laser processing technology is a non-contact processing, its beam diameter is small, high-energy density, high productivity, stable and reliable processing quality. This paper for the laser welding, laser direct writing, laser detection and laser cleaning overview of the four-laser technology in the application of large-scale integrated circuits. And the working principle, type and process characteristics of these laser technologies are discussed. The development of laser technology has also limited the production of large-scale integrated circuits in some aspects. With the semiconductor laser, excimer laser process continues to mature, laser technology in integrated circuits will continue to expand the scope of application and break through the obstacles.

Fabrication of Superhydrophobic–Hydrophilic Patterned Cu@Ag Composite SERS Substrate via Femtosecond Laser

Ultralow concentration molecular detection is critical in various fields, e.g., food safety, environmental monitoring, and disease diagnosis. Highly sensitive surface-enhanced Raman scattering (SERS) based on ultra-wettable surfaces has attracted attention due to its unique ability to detect trace molecules. However, the complexity and cost associated with the preparation of traditional SERS substrates restrict their practical application. Thus, an efficient SERS substrate preparation with high sensitivity, a simplified process, and controllable cost is required. In this study, a superhydrophobic–hydrophilic patterned Cu@Ag composite SERS substrate was fabricated using femtosecond laser processing technology combined with silver plating and surface modification treatment. By inducing periodic stripe structures through femtosecond laser processing, the developed substrate achieves uniform distribution hotspots. Using the surface wettability difference, the object to be measured can be confined in the hydrophilic region and the edge of the hydrophilic region, where the analyte is enriched by the coffee ring effect, can be quickly located by surface morphology difference of micro-nanostructures; thus, greatly improving detection efficiency. The fabricated SERS substrate can detect Rhodamine 6G (R6G) at an extraordinarily low concentration of 10−15 mol/L, corresponding to an enhancement factor of 1.53 × 108. This substrate has an ultralow detection limit, incurs low processing costs and is simple to prepare; thus, the substrate has significant application potential in the trace analysis field.

Retracted: Progress of Laser Processing Technology in Ferroelectric Nanocomposites

Retracted: Progress of Laser Processing Technology in Ferroelectric Nanocomposites

Preparation of Polytetrafluoroethylene Superhydrophobic Materials by Femtosecond Laser Processing Technology.

In recent years, superhydrophobic surfaces have attracted significant attention due to their promising applications, especially in ice prevention, reduction in air resistance, and self-cleaning. This study utilizes femtosecond laser processing technology to prepare different surface microstructures on polytetrafluoroethylene (PTFE) surfaces. Through experiments, it investigates the relationship between the solid-liquid contact ratio and surface hydrophobicity. The shape of water droplets on different microstructure surfaces is simulated using ANSYS, and the relationship between surface microstructures and hydrophobicity is explored in the theoretical model. A superhydrophobic surface with a contact angle of up to 166° was obtained by machining grooves with different spacings in polytetrafluoroethylene sheets with femtosecond laser technology. Due to the micro- and nanostructures on the surface, the oleophobicity of the processed oleophilic PTFE surface is enhanced.

Enhanced capillary performance of multiscale ultrathin titanium wicks guided by modified wicking dynamics

Ultrathin titanium vapor chambers with wicks fabricated by ultrafast laser direct writing provide a promising solution for future electronics' lightweight thermal management. However, despite being a powerful tool for wick manufacturing, the application of ultrafast laser is restricted by its low fabrication efficiency and imperfect model for wick design. Herein, a multiscale titanium wick with stable superhydrophilic nano ripples and microgrooves was high-efficiently fabricated by a multi-beam femtosecond laser processing technology. A modified wicking dynamic model was proposed for ultrafast laser manufactured microgroove wick design. It considered the extra capillary force by laser induced nanoripple and viscous resistance of the narrow V-shape grooves, which is ignored in the classic model. The prediction error of wicking performance reduced from 72.9 % to 4.5 %. Compared to the conventional V-shape design the optimized microgrooves wick improved by 56.7 % and exhibited capillary performance parameter (K/Reff) of 1.88 μm at a thickness of 80 μm, which outperformed most of the recently reported data. The modified model, multiscale high-performance wick, and its highly efficient fabrication method propose a universal and handy approach for accurate and quantitative wick design and manufacturing.

High-Transmission Biomimetics Structural Surfaces Produced via Ultrafast Laser Manufacturing.

Inspired by periodically aligned micro/nanostructures on biological surfaces, researchers have been fabricating biomimetic structures with superior performance. As a promising and versatile tool, an ultrafast laser combined with other forms of processing technology has been utilized to manufacture functional structures, e.g., the biomimetic subwavelength structures to restrain the surface Fresnel reflectance. In this review paper, we interpret the biomimetic mechanism of antireflective subwavelength structures (ARSSs) for high-transmission windows. Recent advances in the fabrication of ARSSs with an ultrafast laser are summarized and introduced. The limitations and challenges of laser processing technology are discussed, and the future prospects for advancement are outlined, too.

The Influence of Laser Process Parameters on the Adhesion Strength between Electroless Copper and Carbon Fiber Composites Determined Using Response Surface Methodology.

Laser process technology provides a feasible method for directly manufacturing surface-metallized carbon fiber composites (CFCs); however, the laser's process parameters strongly influence on the adhesion strength between electroless copper and CFCs. Here, a nanosecond ultraviolet laser was used to fabricate electroless copper on the surface of CFCs. In order to achieve good adhesion strength, four key process parameters, namely, the laser power, scanning line interval, scanning speed, and pulse frequency, were optimized experimentally using response surface methodology, and a central composite design was utilized to design the experiments. An analysis of variance was conducted to evaluate the adequacy and significance of the developed regression model. Also, the effect of the process parameters on the adhesion strength was determined. The numerical analysis indicated that the optimized laser power, scanning line interval, scanning speed, and pulse frequency were 5.5 W, 48.2 μm, 834.0 mm/s, and 69.5 kHz, respectively. A validation test confirmed that the predicted results were consistent with the actual values; thus, the developed mathematical model can adequately predict responses within the limits of the laser process parameters being used.

The synchronous detection technique for the accurate monitoring of high-energy pulsed X-rays

At high energy, the smaller inelastic nucleon-Carbon cross-section implies that diamond has a radiation hardness an order of magnitude higher than that of silicon. The production of high-quality diamond crystals and films grown using the chemical vapor deposition technique opened the way for the use of synthetic diamonds in the fabrication of detectors for charged particles and high-energy photons. More recently, laser-processing technology for the fabrication of three-dimensional contacts in diamond has been proposed to produce highly efficient detectors, even with ultra-low active volumes. However, buried-contact structures made with laser treatments unavoidably induce structural defects in the volume surrounding the buried columns, thus affecting the detector response due to trap-related charge transport mechanisms. When pulsed radiation is concerned, experimental results reported in this work demonstrate that synchronous signal conditioning can strongly mitigate the trap-mediated contribution, thereby improving the performance of the overall detection system. Significantly, these results pave the way for the application of diamond samples with three-dimensional buried-contacts in the development of detectors for accurate dosimetry.

Effect of femtosecond laser bionic texture on anti-wear properties of medical Ti-6Al-4 V

Ti-6Al-4 V (TC4) is used as a medical implant material. However, its wear resistance is poor, which is not conducive to the use of implants. In this study, three biomimetic textures were designed on the surface of materials by femtosecond pulsed laser processing technology. The wear resistance of the textured surface was studied by rotating dry friction. The results demonstrate that the textured surface effectively reduces and captures the generation of wear particles, leading to enhanced stability of TC4 during wear and reduced surface wear. Compared with the untextured surface, the wear of the textured surface is reduced by 73.68%. These results indicate that bionic texture can improve the wear resistance of TC4.

Micro-grooves machining and optimizing on SiC/SiC composites by femtosecond laser-based on response surface methodology

This study applied femtosecond laser processing technology to prepare microgrooves on the surface of SiC/SiC ceramic matrix composites (CMCs). The corresponding parameter ranges for response surface optimization were determined through single-factor experiments. Additionally, four quadratic regression models were established to predict surface roughness, groove width, groove depth, and volume material removal rate. The Analysis of Variance (ANOVA) revealed that the developed model was reliable. Additionally, the study investigated the effects of laser parameters such as power, scanning speed, and defocusing amount, as well as their interactions, on various outcome measures, including the roughness average (Ra), groove width, groove depth, and volume material removal rate (VRR). To optimize the process parameters, the response surface method was employed to achieve maximum VRR and minimum Ra. After conducting the analysis, the optimal processing parameters were determined to be a laser power of 36 W, a scanning speed of 24 mm/s, and a defocusing amount of −1.17 mm. The developed model accurately predicts groove depth, width, volume material removal rate, and surface roughness in SiC/SiC-CMCs processing. The relative deviations between the actual and expected values fall within the acceptable range, affirming model's reliability. This indicates that the model improves precision in predicting these parameters for SiC/SiC-CMCs processing. The findings of this study have significant implications for improving the processing quality and efficiency of SiC/SiC-CMCs and establishing a relationship between processing parameters and responses. These insights can inform future research efforts to optimize these complex materials' manufacturing processes.

Trifolium repens L.-Like Periodic Micronano Structured Superhydrophobic Surface with Ultralow Ice Adhesion for Efficient Anti-Icing/Deicing.

Wind turbine blades are often covered with ice and snow, which inevitably reduces their power generation efficiency and lifetime. Recently, a superhydrophobic surface has attracted widespread attention due to its potential values in anti-icing/deicing. However, the superhydrophobic surface can easily transition from Cassie-Baxter to Wenzel at low temperature, limiting its wide applications. Herein, inspired by the excellent water resistance and cold tolerance of Trifolium repens L. endowed by its micronano structure and low surface energy, a fresh structure was prepared by combining femtosecond laser processing technology and a boiling water treatment method. The prepared icephobic surface aluminum alloy (ISAl) mainly consists of a periodic microcrater array, nonuniform microclusters, and irregular nanosheets. This three-scale structure greatly promotes the stability of the Cassie-Baxter state. The critical Laplace pressure of ISAl is up to 1437 Pa, and the apparent water contact angle (CA) is higher than 150° at 0 °C. Those two factors contribute to its excellent anti-icing and deicing performances. The results show that the static icing delay time reaches 2577 s, and the ice adhesion strength is only 1.60 kPa. Furthermore, the anti-icing and deicing abilities of the proposed ISAl were examined under the environment of low temperature and high relative humidity to demonstrate its effectiveness. The dynamic anti-icing time of ISAl in extreme environments is up to 5 h, and ice can quickly fall with a speed of 34 r/min when it is in a horizontal rotational motion. Finally, ISAl has excellent reusability and mechanical durability, with the ice adhesion strength still being less than 6 kPa and the CA greater than 150° after 15 cycles of icing-deicing tests. The proposed structure would offer a promising strategy for the efficient anti-icing and deicing of wind turbine blades.

Optimization of micropore fabrication on the surface of ultrathick polyimide film based on picosecond UV laser

Micropores fabricated on organic polymer films have a wide range of applications in fields such as microfiltration, new energy, and biomedical separation. The use of laser processing technology can complete the processing of micropores on the surface of ultrathin films with high precision, but there is still some difficulty in the processing of ultrathick films. In this paper, a picosecond ultraviolet (UV) laser was used to explore the high-precision manufacturing process of micropores on the surface of ultrathick polyimide (PI) films. The effects of laser power, laser frequency, and scanning speed on the cone angle and spatter deposition area of micropores’ fabrication on ultrathick PI were studied based on orthogonal experiments. The mechanism of processing micropores on ultrathick PI was analyzed by studying the deposition area and morphology of the spatter generated during the laser ablation process. It was found that high-quality micropores can be fabricated at low laser frequency and high power.

Study on Hydrodynamic Lubrication and Friction Reduction Performance of Cylindrical Rolls With Tesla Valve Texture

Friction and wear seriously affect the efficiency and life of a machine device. The dynamic pressure lubrication and friction properties of the surface are improved by surface texture technology, which plays an extremely important role in reducing friction and wear. In order to maximize the hydrodynamic lubrication and friction reduction performance of surface texture, a Tesla valve surface texture is proposed in this article. The oil film bearing capacity and wall friction of Tesla valve texture are examined through computational fluid dynamics fluid simulation. Cylindrical rolls with Tesla valve texture are prepared by using laser processing technology, and comparative friction wear tests are conducted. The results show that the lubrication performance of Tesla valve texture is four times higher than without this texture. The friction coefficient and wear loss of the cylindrical rolls with Tesla valve texture are, respectively, 39.7% and 66.7% lower than those of the cylindrical rolls without texture. Tesla valve texture effectively improves the dynamic pressure lubrication and friction in the cylindrical rolls.

Anti-Wear Property of Laser Textured 42CrMo Steel Surface

In this work, laser processing technology was utilized to fabricate micro-textures on the surface of 42CrMo steel to improve its wear resistance under high load conditions and provide an effective method to solve the wear of tooth plates in oil drilling wellhead machinery. Firstly, the friction process of the textured components was conducted by finite element analysis. Additionally, various forms of textures were compared and measured by this method to optimize the shape and parameters of the patterns. Secondly, three types of texture shapes, such as micro-dimples, micro-grooves, and reticular grooves, were created on the surface of 42CrMo steel. Lastly, the tribological characteristics of the micro-textures were analyzed in the dry friction experiments. Compared with the untextured surface, the wear resistance of the textured 42CrMo steel has been improved, and the anti-wear property of the micro-dimples was better than micro-grooves and reticular grooves. Along the direction of friction sliding, the wear of the front end is more worn than the rear end. Micro-dimples with a diameter of 0.8 mm, a spacing of 1.2 mm, and an area occupancy of 34.8% were fabricated at an output power of 200 W and a frequency of 5 Hz. The wear of the textured surface has been reduced by more than 80% in the process of ring-block dry friction with a load of 50 N, a rotation speed of 35 r/min, and a time of 15 min. The wear mechanism is mainly abrasive wear. The results showed that the hardness of the surface could be improved by laser hardening. In addition, micro-dimples on 42CrMo steel can store abrasive particles, mitigate the formation of furrows and reduce the abrasive wear of tooth plates.