Laser Etching Research Articles

Automated production of batched unclonable micro-patterns anti-counterfeiting labels with strong robustness and rapid recognition speed

Anti-counterfeiting technologies are indeed crucial for information security and protecting product authenticity. Traditional anti-counterfeiting methods have their limitations due to their clonable nature. Exploring new technologies, particularly those based on pixel-level textures, is a promising avenue to address the clonable issue due to high encoding capacity. However, research in this field is still in its early stages. This work introduces a new fluorescent anti-counterfeiting label technology with four key characteristics: efficient laser etching, high-throughput fabrication and segmentation, robustness aided by data augmentation, and an exceptionally high recognition speed. Specifically, the etching achieves a speed of 1,200 labels/3s, the high-throughput procedures yield a rate of 2,400 labels/4 mins, and the total count is about 5.2 × 104 labels. The number of labels is further augmented to about 5.2 × 106 by implementing arbitrary rotation and brightness variation to enhance the robustness in the recognition procedure. We divide these labels into 44 categories based on differences in patterns. Utilizing machine learning methods, we have achieved a total recognition (including extraction and search process) time per label averaging 421.96 ms without classification, and 40.13 ms with classification. Specifically, the search process with classification is nearly fiftieth times shorter than the non-classification method, reaching 8.52 ms in average. The overall recognition time is much faster than previous works, and achieves an accuracy of over 98.7%. This work significantly increases the practical significance of pixel-level anti-counterfeiting labels.

DESIGN AND FABRICATION OF SHAPE MORPHING MAGNETO-IMPEDANCE MAGNETIC SENSOR

The magnetoimpedance (MI) effect is characterized by the alteration in the impedance of soft magnetic materials when subjected to a magnetic field while a high-frequency alternating current flows through them. In this study, we engineered two distinct sensor architectures utilizing amorphous FeCSi magnetic ribbon: a single-bar structure with the dimension of 10 mm × 90 μm × 20 μm and a meander structure consisting of 13 parallel single bars. These structures were miniaturized through advanced techniques combining laser engraving and chemical etching. The magnetic analysis reveals that the meander structure exhibits a pronounced dependency on the angle θ between the magnetic field and the sensor orientation, enhancing its soft magnetic properties by up to fivefold compared to the single-bar design. This enhancement might be attributed to a reduction in the demagnetization effect and shape anisotropy energy within the meander sensor. Furthermore, the analysis of the MI effect indicates that the resonance frequency remains unaffected by external magnetic fields for both sensor types. Notably, the meander sensor demonstrates exceptional MI ratio values exceeding 82%, representing a remarkable 24-fold increase over the 3.5% observed in the single-bar sensor. Additionally, the isotropy - quantified as the MI ratio's dependence on angle θ, and magnetic field sensitivity are significantly improved in the meander configuration. These advancements in soft magnetic and physical properties are correlated to the domain structure of the sensor, particularly its transverse magnetic permeability, as evidenced by micromagnetic simulations conducted using Mumax3. With its superior MI ratio, isotropy, and heightened magnetic field sensitivity, the meander-type magnetic field sensor presents substantial potential for applications across diverse fields, ranging from biological systems to specialized practical missions.

Flexible Supercapacitor Device Based on Laser‐Synthesized Nanographene for Low‐Power Applications

Laser‐induced graphene (LIG) and laser‐induced reduced graphene oxide (LIrGO) are two relatively recent graphene‐based nanoscale materials suitable for miniaturized flexible supercapacitors. This study employs direct laser engraving techniques to generate patterns on flexible substrates, such as paper and polyamide (PI). This methodology allows fine control over the formed nanographene structures to fabricated LIG and LIrGO supercapacitors. The LIG on PI exhibits a distinctive porous structure and high surface area, adsorption, and transportation of ions. Furthermore, paper‐based LIrGO electrodes are recyclable and are formed in a single step. The morphological study is done using scanning electron microscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. Galvanostatic charge–discharge studies at 0.05 mA cm−2 current density show an areal capacitance of 3.69 mF cm−2 for LIG and 1.61 mF cm−2 for LIrGO. The comparable energy densities for LIG and LIrGO are 0.32 and 0.16 μWh cm−2, respectively. From the calculative analysis of both types, the variation in specific areal capacitance enabling effective is 56.3% from GCD, indicating that the LIG device performs better. Finally, a portable potentiostat is employed to investigate the viability of utilizing supercapacitors to operate self‐powered sensors in a portable and integrable fashion.

Enhancing Performance of Composite-Based Triboelectric Nanogenerators Through Laser Surface Patterning and Graphite Coating for Sustainable Energy Solutions

The performance of composite-based triboelectric nanogenerators (C–TENGs) was significantly enhanced through laser surface patterning and graphite coating. The laser etching process produced accurate and consistent patterns, increasing surface area and improving charge accumulation. SEM imagery confirmed the structural differences and enhanced surface properties of the laser-etched C–TENGs. Graphite fibers further augmented the contact surface area, enhancing charge accumulation and diffusion. Experimental results demonstrated that the optimized C–TENGs, especially those with line patterns and graphite coating, achieved a maximal 98.87 V open-circuit voltage (VOC) and a 0.10 µA/cm2 short-circuit current density (JSC) under a 20 N external force. Environmental tests revealed a slight decrease in performance with increased humidity, while long-term stability tests indicated consistent performance over three weeks. Practical application tests showed the potential of C–TENGs integrated into wearable devices, generating sufficient energy for low-power applications, thereby highlighting the promise of these devices for sustainable energy solutions.

Cartilage Laser Engraving for Fast-Track Tissue Engineering of Auricular Grafts

In this study, the optimal engraving parameters were determined through the analysis of scanning electron microscopy (SEM) data, as follows: a laser power density of 5.5 × 105 W/cm2, an irradiation rate of 0.1 mm/s, a well radius of 60 μm, a distance between well centers of 200 μm, and a number of passes for each well of 20. After 1 week of in vitro cultivation, chondrocytes were located on the surface of the scaffolds, in the sockets and lacunae of decellularized cartilage. When implanted into animals, both cellular and acellular scaffolds were able to support cartilage in-growth and complete regeneration of the defect without clear boundaries with normal tissue. Nevertheless, the scaffolds populated with cells exhibited superior biocompatibility and were not subject to rejection, in contrast to cell-free constructs.

Terahertz laser-fabricated all-polymer hole arrays with high-quality quasi-bound states in the continuum

Abstract Dielectric metasurfaces promise to realize ultrahigh-quality (Q) resonances due to their ultralow material absorption. Most of them are silicon-based metasurfaces, requiring complex fabricated steps and thus suffering high costs. Laser etching processing has simple steps accompanied by low time consumption and exemplary processing efficiency. Here, an all-polymer metasurface based on hole arrays fabricated by laser processing has been proposed and investigated. Such metasurfaces achieve sharp quasi-bound states in the continuum (quasi-BICs) via breaking structural symmetry, form two annular circulation electric fields in different directions, and thus allow strong coupling between holes. Owing to the low refractive index of polymer, the calculated Q-factor reaches 9555 while the diameter discrepancy is 4 μm. Simulated results proved that the Q-factors of quasi-BICs can be further improved by reducing the film thickness and refractive indices of materials, which can be predicted by the fitting equation. Also, the fields in holes can be enhanced by reducing the film refractive index. These results in simulations and experiments provide an alternative method for designing high-Q resonators in terahertz regions.

Laser-engraved defects in TiO2 support: Enhancing reducibility and redox capability of Pt/TiO2 catalyst for reactive and selective hydrogenation

Titanium dioxide (TiO2) has been studied as catalyst or catalyst support in catalysis. Its synthesis or modification approach controls the structural, optical, and electronic properties. Here we applied laser engraving to the anatase TiO2 and studied the consequent changes in its structure and property as well as the properties of TiO2 supported platinum (i.e., Pt/TiO2) catalyst. The laser engraving enlarged the particle size, formed rutile phase and created defects (i.e., oxygen vacancy (Ov) and Ti3+) in anatase TiO2. This induced band gap change and enhanced visible light absorption. The defects created by laser engraving are stable and more reducible than those existed in the pristine TiO2. The defective TiO2 is structurally stable and has great redox properties. The metal-support interaction in the Pt/defective TiO2 catalyst is stronger than that of the pristine Pt/TiO2 catalyst, which enabled higher reactivity and selectivity in hydrogenation of 3-nitrostyrene and furfuryl alcohol. Laser-engraved TiO2 has been rarely studied for thermal catalysis. This work provides basic understanding of material properties and catalysis application of laser-engraved catalyst supports and catalysts in field of thermal catalysis.

Stability Challenges in Industrialization of Perovskite Photovoltaics: From Atomic‐Scale View to Module Encapsulation

AbstractPerovskite photovoltaics have attracted significant attention in both academia and industry, benefiting from the superiorities of high efficiency, low cost, and simplified fabrication process. Importantly, long‐term stability is essential for practical industrialization; however, the stability challenge remains a significant impediment. Notably, stability is an essential prerequisite for practical applications. Unfortunately, as the device area increases, even to the module level, the efficiency gradually diminishes, and the stability deteriorates. This review summarizes the advances in perovskite photovoltaic technology stability from comprehensive perspectives, including the atomic‐scale, grain boundary, film morphology, interface, charge transport layer, electrode, laser etching, and module encapsulation. First, the review highlights the ongoing importance of stability in the industrialization of perovskite photovoltaics. Then, the review presents the stability challenge and explores the relationship between efficiency and stability in large‐area photovoltaic modules, shedding light on the stability issue. Later, the review explains the stability issue in terms of structure, chemistry, interfaces, device design, operation, and external environment, and proposes stability strategies ranging from the atomic‐scale to module encapsulation. Finally, the review emphasizes various improvement strategies, particularly multilevel synergistic optimization, offering fundamental guidance for the industrialization of perovskite photovoltaics.

Enhancing wetting and adhesion of stainless steel (SS304) surfaces with dielectric barrier discharge (DBD) plasma jet treatment

Enhancing the adhesion of coatings to metallic surfaces can be achieved through decontamination and increased surface energy. Among the various techniques used for functionalizing metallic surfaces, such as chemical etching, laser etching, flame treatment, and ultraviolet radiation; dielectric barrier discharge (DBD) plasma stands out as a promising option. It offers low-power, cost-effective, room-temperature operation and provides treatment with minimal alteration of subsurface properties. This study investigates using a DBD plasma jet to increase the treatment area, surface wettability, organic decontamination, and paint adhesion on stainless steel (SS304). The impact of different plasma treatments and aging times on the liquid contact angles and corresponding surface energies are experimentally examined. The results indicate that the surface energy of SS304 increases with treatment time. X-ray photoelectron spectroscopy (XPS) measurements are carried out to correlate this increase in surface energy to an increase in oxide bonds and decontamination of organic species, resulting in surface activation. However, it is observed that the plasma-treated surfaces exhibit no significant alterations in surface morphology, as confirmed through analyses of surface roughness and micro-hardness. Cross-hatch adhesion tests are carried out to demonstrate that the plasma surface treatment results in a significant improvement in surface adhesion to external coatings. Furthermore, the study evaluates the impact of DBD plasma jet treatment speed and dose on coating adhesion, providing valuable insights for making a trade-off between treatment quality and energy efficiency. The findings could extend the applicability of the DBD plasma jet to various areas, including anti-fogging surfaces, water harvesting, paints and coatings, and organic decontamination of surfaces.

A simple method to remove polyimide coating from fused silica capillaries for capillary electrophoresis

A simple and cost-effective method for making capillary electrophoresis (CE) detection windows is reported. A low-cost laser engraving machine equipped with a 450 nm high-power blue laser was used to remove the polyimide coating from the fused silica capillary by laser scanning the desired section. The entire process is automated and controlled in real time by software. This method can be easily adopted by many CE users for routine practice and is scalable for high-throughput production of detection windows across multiple capillaries.

Facilitating water droplet removal from surfaces using air flow and wettability gradients

A new method is proposed to mitigate ice accretions on wind turbine blades via the creation of a microstructural gradient surface geometry that facilitates spontaneous water droplet motion along the surface. The wettability gradients are formed by laser etching 35 μm wide, 35 μm deep channels into aluminum to form a surface with a gradually increasing solid area fraction. Different design variations are then proposed and systematically evaluated on the merits of their performance. An analytical model is also derived based on a balance of hysteresis and drag forces to predict the critical airspeed necessary for droplet movement as a function of the droplet size and surface contact angle. Experimentation has shown good agreement with the model for both the baseline and fixed-pitch channel surfaces and has also demonstrated that, in certain cases, up to 70 % lower critical airspeeds are needed to initiate droplet motion on these microstructured surfaces.

Shear bond strength of a composite resin restoration in primary teeth following cavity preparation using laser- an in-vitro study.

To evaluate and compare the shear bond strength of composite resin restorations in primary teeth, following cavity preparation with both traditional dental burs and laser irradiation. One hundred primary molars extracted from the children visiting our department were collected and randomly divided into five groups (A-E) with 20 teeth in each group. In groups A, B, C, D, and E the teeth samples were etched with phosphoric acid, Er; YAG laser followed by acid etching, Er, Cr: YSGG laser followed by acid etching, Er; YAG laser etching only and Er, Cr: YSGG laser etching only, respectively. Following, all the samples were restored with composite resin and subjected to 500 cycles of thermocycling. The shear bond strength of the resin composite was analyzed. The type of fractures was also noted. Data obtained were subjected to statistical analysis. The mean value of shear bond strength of Group A, B, C, D, and E was 17.562 ± 0.810, 15.928 ± 0.415, 14.964 ± 0.566, 11.833 ± 0.533 and 11.187 ± 0.517, respectively. Adhesive failure was most commonly seen in all the groups. The phosphoric acid etching remains a highly effective technique for pre-treating dentin in composite resin restorations. The shear strength of composite resin to the dentin of laser-prepared cavity in primary teeth can be improved by the addition of acid etching.

Superhydrophobic, Anti-Freezing and Multi-Cross-Linked Wearable Hydrogel Strain Sensor for Underwater Gesture Recognition.

Conductive hydrogel is considered to be one of the most potential sensing materials for wearable strain sensors. However, both the hydrophilicity of polymer chains and high water content severely inhibit the potential applications of hydrogel-based sensors in extreme conditions. In this study, a multicross-linked hydrogel was prepared by simultaneously introducing a double-network matrix, multiple conductive fillers, and free-moving ions, which can withstand an ultralow temperature below -80 °C. A superhydrophobic Ecoflex layer with a water contact angle of 159.1° was coated on the hydrogel using simple spraying and laser engraving methods. Additionally, the smart glove integrating five hydrogel strain sensors with a microprocessor was developed to recognize 12 types of diving gestures and synchronously transmit recognition results to smartphones. The superhydrophobic and antifreezing hydrogel strain sensor proposed in this study emerges promising potentials in wearable electronics, human-machine interfaces, and underwater applications.

Periodic scratching for global laser-induced damage threshold reduction

Mitigating laser-induced damage threshold (LIDT), which quantifies the power consumption during laser processing, is the key factor in optimizing and updating laser processing with lower energy and power. While methods such as material doping, surface roughness modification, and defect induction have shown promise in reducing LIDT, they fall short of providing a comprehensive solution that offers global LIDT reduction and precise LIDT modulation while relying on minimal workpiece preprocessing. To address the issue, we proposed a new periodic scratching strategy. This approach, validated through both simulations and experiments focused on femtosecond laser etching of soda-lime glass workpieces, demonstrates the capability to achieve global LIDT reduction through period modulation and optimization. We envision that this work paves the way for innovative advancements in laser processing techniques.

Self-validating photoelectrochemical/photoelectrochromic visual sensing platform for ciprofloxacin precise detection in milk

BackgroundIn the process of food production, ciprofloxacin (CIP), a highly prescribed fluoroquinolone antibiotic, is often excessively used to reduce the risk of bacterial infection. However, this overuse can cause severe harm to human health, including allergic responses, gastrointestinal complications, and potential renal dysfunction. The development of a robust and precise detection method for CIP is crucial, given the interconnection between food security and human health. Compared to the single-mode detection methods currently in use, dual-mode detection provides enhanced accuracy in detecting results due to its inherent self-validation and self-correction capabilities. ResultsHerein, a photoelectrochemical and photoelectrochromic self-validated dual-mode sensing platform was developed to detect CIP in milk by laser etching method, signal generation (SG) region, signal output (SO) region and conductive channel was integrated on the same fluoide-doped tin oxide electrode and Ti3C2/ZnO composite was modified in the electron SG region, and Prussian blue (PB) was electrodeposited in the SO region. By irradiating the SG region, photogenerated electrons are generated and injected into the SO region through the conductive pathway, resulting in the reduction of the PB to Prussian white (PW). Because the binding of CIP to its specifically recognized aptamers hinders electron transfer, a “Signal-Off” response mechanism can be used for simultaneous quantitative detection of CIP using photocurrent or color changes, which presents a great advantage in the detection process. SignificanceBy integrating different detection mechanisms within a single linear range, the constructed dual-mode sensor has a wide detection range and low detection limit in milk samples. Additionally, it shows good selectivity in anti-interference experiments, providing a new idea for the development of visual analysis and detection platforms for food safety.

Influence of laser absorptivity of CuCr0.8 substrate surface state on the characteristics of laser directed energy deposition inconel 718 single track

An effective method for fabricating copper-nickel bimetallic liquid rocket engine thrust chambers involves utilizing laser directed energy deposition (LDED) technology. However, the state of the substrate surface significantly impacts the LDED process. This study investigates the effects of various substrate treatments on LDED single tracks, using CuCr0.8 high-copper alloy as the substrate and Inconel 718 as the deposition material. The treatments include polishing, sandblasting, laser etching, and cold spraying. Substrate surface roughness, laser absorptivity, molten pool morphology, and microstructure were characterized, and the mechanisms of laser absorptivity change and the different LDED processes were analyzed. The results indicate that the laser-etched surface exhibits the worst surface roughness (Ra 15.20 ± 0.60 μm), the highest laser absorptivity(80.70% at 1080 nm wavelength), the largest deposition width (947.33 ± 29.85 μm), and the maximum number of fine grains among the four substrates. Additionally, the cold-sprayed surface shows the largest deposition depth (237.33 ± 39.04 μm), the minimum number of fine grains and a higher laser absorptivity (66.20% at 1080 nm wavelength). In situ observations of molten pool formation and flow during LDED was conducted using an in situ high-speed high-resolution imaging system. The mechanisms underlying the alteration in laser absorptivity primarily involve the "trapped light" effect and modifications to the surface material. This research is significant as it provides foundational insights for laser processing of highly reflective materials, offering important theoretical and practical implications for engineering applications.

Forming Epoxy Coatings on Laser-Engraved Surface of Aluminum Alloy to Reinforce the Bonding Joint with a Carbon Fiber Composite

This study designed laser engraving and resin pre-coating (RPC) treatments on an aluminum alloy (AA) surface to construct through-the-thickness “epoxy pins” for improving the bonding strength with carbon fiber reinforced polymer (CFRP). A laser engraving treatment was used to create a pitted structure on the AA surface; higher wettability was acquired and greater vertical spaces were formed to impregnate epoxy resin, resulting in stronger mechanical interlocking. The RPC technique was further used to guide high-viscosity epoxy resin into pits to form the epoxy coatings and to minimize defects between the resin and the substrate. The bonding strength of the specimen treated with both laser engraving with a unit dimension of 0.3 mm and RPC increased up to 227.1% in comparison with that of the base. The failure modes of the hybrid composites changed from the debonding failure of the AA surface to the delamination-dominated failure of the laminated CFRP composites. It was confirmed that laser engraving is a feasible and effective method when combined with RPC for treating AAs to improve the bonding strength of AA-CFRP composites, which provides a reference for preparing high-performance hybrid composites with metals.

Pulsed focused ultrasound ablation assisted by a surface modified catheter for thrombolysis: a feasibility study

Interventional procedures for the recanalization of blood vessels to treat deep vein thrombosis carry a high risk of vessel wall injuries or hemorrhaging. Focused ultrasound (FUS) has been used to non-invasively break down blood clots that occlude the vessels in both in vitro and in vivo studies. Previous studies have either used thrombolytic drugs or ultrasound contrast agents (e.g., microbubbles) in combination with FUS. Several studies have applied very high peak-negative-pressures (PNP) during FUS treatment to achieve successful thrombolysis without the use of contrast agents. In the current study, we demonstrated that cavitation activity could be significantly enhanced by placing a nitinol wire, whose surface was roughed by laser etching, in the focal region of a FUS field. We demonstrated in vitro in a mock thrombosis that the thrombolysis efficacy of a 500 kHz FUS transducer was significantly enhanced using a surface-etched nitinol wire as compared to an unetched nitinol wire, whereas FUS-alone at the same pressure level did not result in any thrombolysis. These results suggest that a surface modified nitinol catheter exposed to FUS can result in intense cavitation activities leading to enhanced thrombolysis without the use of additional pharmacological or contrast agents.

Laser wounding pattern in relation to vascular tissue development for the stimulation of adventitious root formation in rose cuttings

The stimulation of adventitious root formation from laser-wounded rose cuttings in our previous study suggests that exposing the phloem proximities is one of the most relevant aspects for a positive effect on rooting response. But, the specific dimensions that wound patterns must fulfill to optimize rooting promotion remain unknown. This study analyzed the effect of wounded area and wound perimeter of laser marking patterns on the development of phloem, xylem, and callus using cross sections of single-leaf cuttings of Rosa canina 'Pfänder'. Four distinct laser patterns were designed and marked along the cutting base. Among these, three patterns were based on longitudinal strips, while one pattern was characterized by small squares, resulting in two distinct wound area levels and four wound perimeter levels. Periodic evaluations of stem sections showed that the development of phloem and xylem was significantly influenced by the pattern's geometry. Larger dimensions of xylem were associated with patterns of greater area and a smaller perimeter, while an increase in phloem was related to patterns of longer perimeter distributed in smaller areas. The maximum rooting success in wounded cuttings reached 44% in contrast to 9% observed in the control group in the absence of additional wounds. The development of vascular tissue was significantly correlated with adventitious rooting, with phloem being more closely linked with a Pearson coefficient of 0.92 compared to 0.30 for xylem. Additionally, a negative Pearson coefficient of −0.92 between the ratio area: perimeter and adventitious root formation showed that laser patterns with large wounded area with less borders led to a reduced rooting response. The results provide evidence of how wounded tissue contributes to the intrinsic development of adventitious roots and reveal the importance of proper wound dimensions.

Enhanced anti-icing performance of novel superhydrophobic F-L@KH-SiO2/OTMS coating synergistic preparation with bionic micro-nano structures and modified nanoparticles

Surface icing significantly impacts equipment operation and safety in low-temperature environments. Passive de-icing technologies using superhydrophobic materials are gaining attention for their environmental and cost benefits. This study presents a novel superhydrophobic F-L@KH-SiO2/OTMS coating, fabricated through femtosecond laser etching of aluminum alloy to create bionic micro-nano lattice structures. Subsequently, a hydrophobic epoxy coating was sprayed as an adhesive layer, followed by chemical modification of the ablated aluminum alloy surface using 3-(trimethoxysilyl) propyl methacrylate (KH570) modified silicon dioxide (SiO2) nanoparticles, γ-aminopropyltriethoxysilane (KH550), and octadecyltrimethoxysilane (OTMS) as hydrophobizing agents. The resulting coating exhibits excellent superhydrophobic properties, with a contact angle (CA) of 165.92° and a sliding angle (SA) of only 1.25°. The coating demonstrated superior anti-adhesion and bouncing capabilities, effectively preventing droplet freezing and ice formation, which is attributed to the synergistic effect of the modified silica and the cross-linked lattice structure. Compared to other reported superhydrophobic surfaces, this coating showed a longer freezing delay time of 730 s at −20 °C. These findings highlight the potential of the F-L@KH-SiO2/OTMS coating for efficient anti-icing, de-icing, and defrosting applications.