Laser printing of silicon-containing multilayer anodes with optimized electrode inksRist, U.; Pfleging, W.
doi: 10.1117/12.3042057pmid: N/A
The demand for improved and affordable batteries is increasing with the further decarbonization of mobility and other parts of the industry. To further improve lithium-ion technology, high-capacity materials such as silicon must be introduced to increase the energy density of the batteries. Furthermore, customized electrode architectures can help to improve the cycle stability and thus increase the acceptance for batterie powered mobility and mobile devices. For this purpose, multilayer electrodes were printed with the laser-induced forward transfer process, using inks with different active materials for the different layers. As active materials the high-capacity material silicon and the state-of-the-art material graphite were used. The electrodes were assembled in coin cells against lithium and were electrochemically analyzed. The prepared cells have twice the specific capacity compared to pure graphite electrodes due to the addition of silicon. After cycling, the cells were disassembled. Here, no lithium plating or deformation of the current collector was detected.
Autonomous ultra short pulse ablation process design with Bayesian optimizationKröger, Moritz; Bornschlegel, Benedikt; Kaster, Thomas; Hinke, Christian; Holly, Carlo
doi: 10.1117/12.3039141pmid: N/A
Ultra-short pulse laser ablation allows precise material removal with minimal thermal damage through femtosecond to picosecond laser pulses. This study explores the autonomous optimization of the critical process parameters pulse energy and pulse overlap. Traditional methods for characterizing materials are often labor-intensive and time-consuming. In contrast, we propose a fully automated Bayesian optimization procedure to streamline material characterization, focusing on maximizing specific removal rates while minimizing surface roughness. An experimental setup at the Chair for Laser Technology at RWTH Aachen integrates advanced sensors and a microservice-based software platform to facilitate real-time optimization. The results demonstrate the efficiency of Bayesian optimization in exploring multi-objective parameter spaces, generating a Pareto front that balances productivity and quality. Limitations of the approach are discussed as well.
Highly efficient synthesis of solid-solution alloy nanoparticles by laser-induced reduction for industrial applicationsNakamura, T.; Kuroda, R.; Fukuda, S.; Ina, H.
doi: 10.1117/12.3044369pmid: N/A
Laser-induced Reduction (LRL) is a physicochemical method for synthesizing nanoparticles by irradiating a solution containing metal ions with high-intensity pulsed laser light. It is simple and environmentally friendly because it does not require reducing agents or high-temperature, high-pressure environments for nanoparticle synthesis. In this method, solid-solution alloy nanoparticles are synthesized by the reduction of metal ions by short-lived radical species generated by the decomposition of solvent molecules in the high-intensity reaction field near the laser focus. In this study, we investigated improvement of the efficiency of nanoparticle synthesis in the LRL method using chemical and optical approaches. In the chemical approach, it was confirmed that the efficiency of nanoparticle synthesis increased by about nine times with the addition of glycerin which is a scavenger for oxidation radicals. Furthermore, the addition of the scavenger also made it possible to synthesize nanoparticles even when the concentration of metal ions in the solution was increased. As a result, the efficiency of nanoparticle synthesis increased by more than 18 times compared to conventional conditions. In the optical approach, two cylindrical lenses were used to focus laser light at two points on the laser axis. It was found that the production efficiency could be improved by up to 1.4 times by changing the distance between the two cylindrical lenses. By combining the chemical and optical approaches, it was shown that the nanoparticle production efficiency could be improved by around 25 times compared to conventional methods. This corresponds to 200 g/month of gold nanoparticles.
Micro-laser assisted machining (-LAM) for ultra-hard and brittle optical materialsKode, Sai; Stepanova, Tatiana; Tsegaye, Anteneh A.; Menon, Deepak Ravindra
doi: 10.1117/12.3043696pmid: N/A
Materials like fused silica and borosilicate crown glass (N-BK7) have strong covalent Si-O bonds that make them hard but brittle due to the lack of dislocations for plastic deformation. Furthermore, materials such as tungsten carbide (WC) and silicon carbide (SiC) are extremely hard and brittle materials due to their strong covalent bonds (W-C in WC and Si-C in SiC), with SiC also exhibiting sp3-sp3 bond lengths that result in tightly packed atoms, further enhancing its resistance to deformation and breakage. Machining such materials is challenging; however, Micro-Laser Assisted Machining (-LAM) offers a promising solution. By applying laser energy to soften hard and brittle materials locally, -LAM facilitates the machining process, making it feasible to shape these hard materials. This study uses a Universal Mechanical Tester (UMT) to evaluate the cutting performance of brittle optical materials such as fused silica and tungsten carbide under various conditions, with and without laser assistance. By integrating a laser with a diamond cutting tool, improvements in material removal rates, surface quality, and overall cutting efficiency were evaluated. The experimental setup involves testing multiple rake angles to determine acceptable parameters for each material. The materials’ response to -LAM is meticulously analyzed through metrology and microscopic examination, focusing on surface integrity, ductile-brittle transition, and subsurface damage. The results demonstrated that -LAM significantly improves cutting performance by reducing cutting forces and enhancing surface finish. Optimized rake angles, nose radius, and laser parameters yield the best results, paving the way for more efficient and precise machining of hard and brittle optical materials.
Ultrafast laser cable markingYuan, Lei; Cheng, Xiaole; Smith, Curtis
doi: 10.1117/12.3044762pmid: N/A
We summarized our recent research progress on outdoor cable identification and length marking using laser technology compared to the conventional inkjet printing method. By inducing a photochemical effect within the polymer matrix, periodic surface features at micro and nano scales were directly created onto a standard cable jacket using an ultrafast laser system. In addition to meeting industry standards for durability, the laser marking also fulfills practical requirements such as contrast and abrasion resistance. This demonstrates the potential for high-speed laser marking on polyethylene (PE) cable without the need to reduce carbon black or add costly laser additives.
Investigation of phase distribution of fiber fuse in bulk glass through shadowgraph observation with NUV backlightSato, Masataka; Itoh, Sho; Matsusaka, Souta; Hidai, Hirofumi
doi: 10.1117/12.3042565pmid: N/A
Fiber fuse is a destruction phenomenon induced in fibers, whereas applying the drilling technique with fiber fuse in bulk glass is proposed. Previous work predicted that the moving bright spot contains a void filled with gas, surrounded by a liquid phase. However, actual phase distribution has not been observed due to the high brightness caused by heat radiation and plasma emission. In this study, we employed high-speed shadowgraph observations with near-ultraviolet backlight to reveal the phase distribution within the bright spot. Fiber fuse was induced in bulk fused silica using a 1064 nm Continuous-Wave (CW) laser. As a result, when the bright spot reached the glass surface, the strong emission disappeared immediately, and a void appeared. Subsequently, the weak emission around the void faded gradually, and the solidified glass appeared. This result supports the theory proposed in previous work and contributes to understanding the principle underlying fiber fuse drilling.
Controlling the morphology of 2D laser-induced periodic surface structures (LIPSS) for surface-enhanced Raman spectroscopy applicationsBaskar, Balaji; Ahad, Atiqul Islam; Berrospe-Rodriguez, Carla; Aguilar, Guillermo
doi: 10.1117/12.3040396pmid: N/A
The creation of Laser-Induced Periodic Surface Structures (LIPSS) with near-submicron dimensions has significantly altered the surface properties of materials, as demonstrated in the past decade. These properties, particularly the hydrophobic characteristics, can be enhanced when combined with the dense nanostructures in LIPSS, making them ideal for highly Sensitive Surface-Enhanced Raman Spectroscopy (SERS) applications. However, a key challenge lies in precisely controlling the morphology of these nanostructures and their surface contact properties to effectively concentrate analyte molecules in specific regions for detection at extremely low concentrations. Here we show how single and double femtosecond laser pulse irradiation can be used to achieve different LIPSS morphologies. We generate 1D and 2D periodic nanostructures on 304 stainless steel substrates by adjusting the polarization and inter-pulse delay between fs pulses. From the preliminary experimental results, the dense hotspots in these LIPSS-based sensors allow for the detection of Rhodamine 6G at concentrations as low as 10−10 M, with an analytical enhancement factor of 2 × 107 for consistent and repeatable measurements. These findings provide important insights into the control of laser-induced submicron morphologies by adjusting experimental parameters, offering a straightforward and cost-efficient approach for detecting molecules at ultra-trace levels.
Decoupling laser process parameters and 5D trajectory generation using position-based pulse control mechanismsBelski, Eric T.
doi: 10.1117/12.3041922pmid: N/A
A method is proposed that enables laser process parameters to be optimized and controlled separately from the motion profile using position-based pulse control mechanisms. This method allows new laser processes to be extended to existing motion profiles and viceversa, decreasing the overall development time required for production-ready processes. Features are machined in stainless steel using position-based firing, at optimized profile velocities, while adjusting laser process parameters. The features are machined again using fixed frequency firing approaches, exhibiting drawbacks and interdependence of laser parameters with profile velocity.
Damage free UV-laser pretreatment of thermoplastics for paint applicationsLukasczyk, T.; Veltrup, M.; Keil, A.; Ihde, J.; Delmdahl, R.
doi: 10.1117/12.3041857pmid: N/A
Surface pretreatment of a high-performance thermoplastic (CFRP) to improve paint adhesion was investigated using a UV excimer laser at a wavelength of 248 nm. A focus was given on the influence of different release media (release foil or wet-chemical release agent) on the initial state of the CFRP surface and the adhesion properties for a solvent- and water-based chromate-free primer system after UV laser treatment compared to state-of-the-art compressed air blasting. It could be shown that the application of a release foil for component production leads to relatively low silicon content on the substrates compared to pure silicon-organic release agent. Yet, a crosscut test exhibits bad adhesion properties for both types of differently prepared samples after compressed air blasting, especially if a water-based primer is applied. In contrast, UV excimer laser treatment results in optimal adhesion conditions, independent of the applied release method and coating system. The good paint adhesion after UV laser treatment is also visible after long-term ageing in water or under warm and humid conditions. This effect is contributed to the removal of residues from the release film or agent without a detachment of fibers from the thermoplastic matrix. Furthermore, the laser treatment is adaptable to compact UV excimer laser sources, enabling a higher treatment flexibility and the possibility to treat large scale components.
Piercing shape control of PTFE film by short-pulse CO2 laser with controllable parametersNegishi, Katsunori; Uno, Kazuyuki
doi: 10.1117/12.3041708pmid: N/A
We investigated the processing characteristics of PTFE films using a short-pulse CO₂ laser with controllable parameters. The laser pulse, with a spike pulse width of 200 ns and a pulse tail length of 36.4 s, operated with either a flat-top beam or a doughnut beam at a repetition rate of 200 Hz. The lens had a focal length of 38.1 mm. PTFE films were placed at the focal point or at out-focus distances ranging from 0.00 mm to 1.80 mm. The thickness of the PTFE films ranged from 50 m to 300 µm. The flat-top beam produced a conical hole at the focal point. With an increase in the out-focus distance and the number of pulses, the shape changed to cylindrical, and the taper angle was controlled. The doughnut beam produced cylindrical holes at out-focus distances of 0.20 mm or more, largely unaffected by the number of pulses.