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This study aims to investigate ultraviolet (UV) laser patterning QR codes on printed circuit boards (PCBs) for the inventory management of image recognition. The developed technology is a green manufacture and can replace the harmful environmental substances of brominated epoxy resin ink for the PCB process. In this study, the recognizability of the laser-patterned QR codes and the relationship between the ablated depth and the color change were investigated. The gray relational analysis (GRA) method was adopted to obtain the optimal laser patterning parameters. Furthermore, a spectrophotometer, scanning electron microscope, laser confocal microscope, and spectrometer were used to examine the light absorbance, the ablated depth, the pattern morphology, and the change in light reflectance of the laser-patterned QR codes on PCBs, respectively. The laser-patterned results revealed that QR codes produced white images with an ablation depth ranging from 5 to 10 μm as the scan speed was 300 mm/s at a laser power of 2 W and the scan speed was 900 mm/s at a laser power of 3—6 W. Moreover, the light reflectance of the white sample was close to 0.3819—0.3139, which was a parameter for successful whitening and was easy to recognize by a smartphone app. According to GRA results, the recognized QR code image could be patterned by the parameters of 2 W laser power, 300 mm/s scan speed, and 60 μm scan space. Furthermore, the scan speed was a severe impact factor for laser-patterned QR codes.

In cardiac tissue engineering cells are seeded within porous biomaterial scaffolds to create functional cardiac patches. Here, we report on a bottom-up approach to assemble a modular tissue consisting of multiple layers with distinct structures and functions. Albumin electrospun fiber scaffolds were laser-patterned to create microgrooves for engineering aligned cardiac tissues exhibiting anisotropic electrical signal propagation. Microchannels were patterned within the scaffolds and seeded with endothelial cells to form closed lumens. Moreover, cage-like structures were patterned within the scaffolds and accommodated poly(lactic-co-glycolic acid) (PLGA) microparticulate systems that controlled the release of VEGF, which promotes vascularization, or dexamethasone, an anti-inflammatory agent. The structure, morphology, and function of each layer were characterized, and the tissue layers were grown separately in their optimal conditions. Before transplantation the tissue and microparticulate layers were integrated by an ECM-based biological glue to form thick 3D cardiac patches. Finally, the patches were transplanted in rats, and their vascularization was assessed. Because of the simple modularity of this approach, we believe that it could be used in the future to assemble other multicellular, thick, 3D, functional tissues.

Efficient flexible perovskite solar cells and modules were developed using a combination of SnO 2 and mesoporous-TiO 2 as a fully solution-processed electron transport layer (ETL). Cells using such ETLs delivered a maximum power conversion efficiency (PCE) of 14.8%, which was 30% higher than the PCE of cells with only SnO 2 as the ETL. The presence of a mesoporous TiO 2 scaffold layer over SnO 2 led to higher rectification ratios, lower series resistances, and higher shunt resistances. The cells were also evaluated under 200 and 400 lx artificial indoor illumination and found to deliver maximum power densities of 9.77 μW/cm 2 (estimated PCE of 12.8%) and 19.2 μW/cm 2 (estimated PCE of 13.3%), respectively, representing the highest values among flexible photovoltaic technologies reported so far. Furthermore, for the first time, a fully laser-patterned flexible perovskite module was fabricated using a complete three-step laser scribing procedure (P1, P2, P3) with a PCE of 8.8% over an active area of 12 cm 2 under an illumination of 1 sun.

Highlights First holistic review: It provides the first systematic review encompassing the entire spectrum of laser processing techniques from doping and ablation to crystallization and contact optimization within the context of the complete high-efficiency c-Si solar cell manufacturing chain (passivated emitter and rear cell, tunnel-oxide-passivated contact, heterojunction, and back contact). Enabler for next-generation cells: It critically highlights the role of laser processing as a key enabling technology for overcoming specific fabrication bottlenecks essential for the commercialization of next-generation cell architectures. Laser processing has emerged as a critical enabling technology in the manufacturing of high-efficiency crystalline silicon (c-Si) solar cells. This review systematically examines the fundamental principles and applications of laser technology within the photovoltaic industry. It begins by analyzing the critical influence of laser parameters on the laser–material interaction mechanisms, which ultimately determine the processing quality and the extent of thermal damage. A concise historical overview traces the evolution of laser applications from early laboratory research to later large-scale production of crystalline silicon solar cells. The core of the review is dedicated to a detailed discussion of specific application domains: the utilization of laser thermal effects for doping, oxidation, and crystallization; laser patterning for creating selective emitters, opening passivation layers, and defining intricate structures; and the revolutionary role of lasers in advanced metallization techniques, notably laser pattern transfer printing and laser-assisted sintering. Finally, the review outlines future development trends, highlighting the potential of ultrafast lasers, their integration with novel tandem cell concepts, and the rise of smart, multi-functional stations to push the efficiency and cost-effectiveness of c-Si solar cells.

Purpose The paper aims to investigate the possibilities to control friction in lubricated systems by surface patterning, making use of a multi-scale approach. Surface patterns inside the tribological contact zone tend to directly reduce friction, whereas surface patterns located in the close proximity of the contact area can improve the tribological performance by avoiding lubricant starvation and migration. Finally, optimized surface patterns were identified by preliminary laboratory tests and transferred to a journal bearing, thus testing them under more realistic conditions. Design/methodology/approach Surface patterns on a large scale (depth > 10 µm) were fabricated by micro- and roller-coining, whereas surface patterns on a small scale (depth < 2 µm) were produced by direct laser interference patterning. The combination of both techniques resulted in multi-scale surface patterns. Tribologically beneficial surface patterns (verified in ball-on-disk laboratory tests) were transferred onto a journal bearing’s shaft and tested on a special test-rig. To characterize the lubricant spreading behavior, a new test-rig was designed, which allowed for the study of the lubricant’s motion on patterned surfaces under the influence of a precisely controlled temperature gradient. Findings All tested patterns accounted for a pronounced friction reduction and/or an increase in oil film lifetime. The results from the preliminary laboratory tests matched well, with results from the journal bearing test-rig, both tests showing a maximum friction reduction by a factor of 3-4. Numerical investigations, as well as experiments, have shown the possibility to actively guide lubricant over patterned surfaces. Smaller periodicities, as well as greater structural depths and widths, led to a more pronounced anisotropic spreading and/or greater spreading velocities. Multi-scale surfaces demonstrated the strongest effects regarding the lubricant’s spreading behavior. Originality/value Friction, as well as lubricant migration, can be successfully controlled by using micro-coined, laser-patterned and/or multi-scale surfaces. To the best of the authors’ knowledge, the study demonstrates for the first time the unique possibility to transfer results obtained in laboratory tests to a real machine component.

The interfacial topography of biomaterials has been identified as a major biophysical regulator of cell behavior and function, a role played through the interplay with biochemical cues. In this work, we demonstrate the potential of laser as a versatile technology for the direct fine-tuning of the topography of Bacterial nanocellulose (BNC) with bioinspired topographies and micropatterns on a cell size scale. Two lasers were used, with different wavelengths—IR (CO2, 10600 nm) and UV (tripled Nd: YVO4, 355 nm) —attempting to reproduce the Pitcher-plant topography and to create cell-contact guidance patterns, respectively. Different topographies with parallel grooves featuring a 20–300 μm period were generated on the BNC surface with high fidelity and reliability of the generated microstructures, as demonstrated by 3D optical profilometry and scanning electron microscopy. Moreover, it was demonstrated by X-ray photoelectron spectroscopy that laser processing does not result in detectable chemical modification of BNC. The developed anisotropic microstructures can control cell behavior, particularly regarding morphology, alignment, and spatial distribution. Thus, this proof-of-concept study on the high-resolution laser patterning of BNC opens new perspectives for the development of cell-modulating laser-engineered BNC interfaces, scaffolds, and other advanced medical devices, which can potentially broaden the application of BNC in the biomedical field.

Lasers are being used for modifying the surfaces of biomaterials to make them resistant to microbial adhesion. However, the effect of such surface modification on physical and mechanical properties has not been widely reported. The aim of the study was to investigate the effect of surface modification using laser patterning on the physical and mechanical properties of denture base materials. Nd: YAG nanosecond laser was used to create different patterns on two commercial denture base materials. Surface characteristics of the patterned specimens such as surface roughness, contact angle and resistance to microbial adhesion were measured. Laser patterned specimens with lower microbial adhesion were subjected to evaluation of mechanical (flexural strength and surface hardness) and physical (water sorption and solubility) properties using standard methods. Laser patterning increased the surface roughness, contact angle and the resistance to microbial adhesion. Laser patterning did not have any detrimental effects on mechanical and physical properties. However, a significant increase in surface hardness was observed in all patterned specimens. By fine-tuning the laser patterning parameters, it is possible to create surfaces with enhanced resistance to microbial adhesion without compromising the physical and mechanical properties of the material, which can ultimately lead to better oral health outcomes for denture users.

Micro- and nanoscale structures produced on surfaces of metals, polymers, ceramics, and glasses have many important applications in different fields such as engineering, medical, biological, etc. Laser ablation using ultrashort pulses has become the prominent technique for generating different surface structures for various functional applications. Ultrashort laser ablation proved to be ideal for producing structures with dimensions down to the nanometre scale. In comparison to other texturing techniques employed to create micro/nano features such as electrochemical machining, micro-milling, ion-beam etching, hot embossing, lithography, and mechanical texturing, ultrashort laser ablation produces high-quality surfaces at low cost in a one-step non-contact process. Advantageous characteristics of polymers such as high strength-to-weight ratio, non-corrosive nature, and high electrical and thermal resistance, have made polymers the preferred choice compared to other materials (e.g., steel, aluminium, titanium) in several fields of application. As a result, laser ablation of polymers has been of great interest for many researchers. This paper reviews the current state-of-the art research and recent progress in laser ablation of polymers starting from laser-material interaction, polymer properties influenced by laser, laser texturing methods, and achievable surface functionalities such as adhesion, friction, self-cleaning, and hydrophilicity on commonly used polymeric materials. It also highlights the capabilities and drawbacks of various micro-texturing techniques while identifying texture geometries that can be generated with these techniques. In general, the objective of this work is to present a thorough review on laser ablation and laser surface modification of a variety of industrially used polymers. Since direct laser interference patterning is an emerging area, considerable attention is given to this technique with the aim of forming a basis for follow-up research that could pave the way for potential technological ideas and optimization towards obtaining complex high-resolution features for future novel applications.

A selective laser patterning technique applied inside photomasks as a practical method to mitigate critical-dimension non-uniformity caused by overexposure in large-area lithography systems with segmented illumination was investigated. The geometric characteristics of laser-induced voids were analyzed depending on various laser patterning conditions, and the resulting critical-dimension behavior was evaluated across regions with various transmittance levels, including sharply discontinuous transmittance boundaries. The results show that the void size and morphology can be tuned by adjusting the laser pulse energy, although excessive pulse energy leads to mask fracture, from which we derived appropriate processing windows. Furthermore, photomask transmittance was controllable over a wide range (20–92%) by varying laser parameters, void density, pattern arrangement, and the number of patterned layers. This enabled critical-dimension compensation with nanometer- to tens-of-nanometer-level precision. To examine critical-dimension behavior under abrupt transmittance transitions analogous to overexposure zones, 80% and 50% transmittance regions were placed adjacently. Despite the 30% transmittance difference, critical-dimension variation remained smooth, confirming that sharp transmittance changes do not induce abrupt critical-dimension shifts. Overall, our findings experimentally demonstrate that selective and direct laser patterning inside photomasks is a practical and effective critical-dimension compensation approach for large-area lithography employing segmented illumination systems.

Bifacial semi-transparent perovskite (PVSK) solar cell is a promising candidate to achieve high photo-electrical conversion efficiency (PCE) in a tandem structure with Si solar cells. The gap between lab-scale cells and large area modules needs to be closed using innovative patterning technology. In this paper we demonstrate that a single nanosecond pulsed laser (wavelength 532 nm, pulse duration 7 ns) can be used to perform all scribing processes, i.e. P1, P2 and P3, to manufacture PVSK solar modules. Compared to picosecond or femtosecond lasers reported in the literature, our approach has the advantages of high stability and low cost, and is thus applicable to large scale manufacturing of PVSK solar modules. Detailed laser processing parameters such as laser power and overlap ratio etc. have been studied to achieve optimal results for each scribing process. A mini module with two cells was fabricated on a 2 × 2 cm 2 substrate, showing an active area efficiency of 12.5%, FF of 72.4%, and high GFF of 94%.