United States

Controlling the wetting characteristics of fluids (oil and water) on surfaces is highly desirable for a variety of industrial processes, such as painting, bonding, and lubrication applications. This can be achieved by altering the surface chemistry and/or topography of a material, which can be accomplished through a variety of techniques, including plasma treatment, chemical modification, surface coatings as well as microprocessing methods such as direct laser writing and direct laser interference patterning.&lt;br&gt;
This study summarizes recent developments in the field of functionalization of polymer surfaces, including polyethylene terephthalate (PET), polycarbonate (PC) and polytetrafluoroethylene (PTFE) using hot-embossing methods as well as direct laser fabrication approaches.&lt;br&gt;
The influence of different hot embossing parameters on the resulting texture topography was investigated. In case of the oil wettability tests (on PET), a method to characterize its spreading behavior was developed, allowing a comparison between the produced surface textures. In particular, a superoleophilicity state was reached, in which the contact angle approached zero. Furthermore, hierarchical structured surfaces showed fast wetting rates up to 1.4 mm²/s.&lt;br&gt;
Regarding water-wettability, the microstructured PET surfaces showed an increased hydrophobic state rising from 76° on the flat reference up to 120°. In case of PC, similar results are obtained, reaching 140°, whereas on PTFE surfaces a super-hydrophobic state was achieved, characterized by water contact angles over 150° and a very small hysteresis (&amp;lt; 5°).

ICALEO 2023

Water and Oil Wettability Customization by Tailoring Micro-Structured Polymers

hot-embossing

dlip

microstructured polymers

water and oil wettability

Controlling the wetting characteristics of fluids (oil and water) on surfaces is highly desirable for a variety of industrial processes, such as painting, bonding, and lubrication applications. This can be achieved by altering the surface chemistry and/or topography of a material, which can be accomplished through a variety of techniques, including plasma treatment, chemical modification, surface coatings as well as microprocessing methods such as direct laser writing and direct laser interference patterning. 
This study summarizes recent developments in the field of functionalization of polymer surfaces, including polyethylene terephthalate (PET), polycarbonate (PC) and polytetrafluoroethylene (PTFE) using hot-embossing methods as well as direct laser fabrication approaches. 
The influence of different hot embossing parameters on the resulting texture topography was investigated. In case of the oil wettability tests (on PET), a method to characterize its spreading behavior was developed, allowing a comparison between the produced surface textures. In particular, a superoleophilicity state was reached, in which the contact angle approached zero. Furthermore, hierarchical structured surfaces showed fast wetting rates up to 1.4 mm²/s. 
Regarding water-wettability, the microstructured PET surfaces showed an increased hydrophobic state rising from 76° on the flat reference up to 120°. In case of PC, similar results are obtained, reaching 140°, whereas on PTFE surfaces a super-hydrophobic state was achieved, characterized by water contact angles over 150° and a very small hysteresis (&lt; 5°).

poster

**General Chair Welcome**

![](https://assets.underline.io/markdown_image/1/image/d6e6dddc08bf2371b9136ea9c18dc5ab.png)              

Welcome to ICALEO® 2023!
	
We were excited to host the world’s leading international conference on Lasers and Electro-Optics in Chicago. The Laser has been shown to have the potential to revolutionize solutions for major global challenges like energy usage and supply, global warming, and CO2 footprint. Even the fusion energy breakthrough is based on laser technology. The conference, with peer-reviewed scientific and technical presentations, focused on the newest results in Micro Applications, Macro Applications, Additive Manufacturing, Beam Shaping and Frontiers in Laser Applications. Additionally, the Battery-Manufacturing Track gave an overview of the process combined with the newest advances in laser application results. 

The Business Session brought the business aspect and environment of the laser to the audience and the possibility to discuss with seasoned industry leaders from around the world. 

Whether this is the first time you are hearing about ICALEO or you are a longtime attendee, you will find something of interest, new ideas, and an excellent opportunity to network with other laser specialists worldwide. 

**Klaus Löffler **  
ICALEO General Chair   
Managing Director, Precitec GmbH

**What is ICALEO?**

ICALEO® brings together the brightest minds, seasoned professionals, and pioneering researchers from around the world. With a laser-focused agenda, ICALEO offers an exceptional platform to delve into the cutting-edge advancements, diverse applications, and transformative research that define lasers and electro-optics.

Participants will be immersed in a dynamic environment that fosters collaborative learning, networking, and idea exchange. Through engaging plenary presentations, technical sessions, an industry business panel, and networking events, attendees gain insights into the forefront of laser technology. From industrial applications to medical breakthroughs, additive manufacturing to materials processing, ICALEO covers the entire spectrum of laser-related disciplines. Moreover, the event serves as a launching pad for synergistic partnerships, paving the way for professionals to forge connections that shape the future of our industry.

Join us in Chicago and be part of an unparalleled gathering that challenges the boundaries of possibility within lasers and electro-optics. As we convene to share knowledge, explore innovations, and cultivate collaborations, ICALEO stands as a pivotal force driving the evolution of this transformative technology.

**Who attended?**

ICALEO is tailor-made for professionals, researchers, academics, and enthusiasts who are deeply passionate about the world of lasers and electro-optics. If you're an industry trailblazer, an academic luminary, an aspiring expert, or a postgraduate student looking to dive into the latest developments and trends, this is an event you won't want to miss.

Industrial leaders seeking to stay ahead of the curve in their fields, engineers working on laser applications, and manufacturing experts interested in additive manufacturing and materials processing will find ICALEO to be an invaluable platform. Researchers and scientists exploring the forefront of laser technology, from fundamental principles to groundbreaking applications, will also discover a wealth of knowledge and networking opportunities.

Medical professionals investigating laser-based medical advancements, entrepreneurs seeking to innovate with lasers, educators aiming to stay updated with the latest in laser education, and policy makers shaping the industry's landscape are all essential attendees. Whether you're an established expert or a rising star, the 42nd annual ICALEO promises to offer a diverse ecosystem of expertise, connections, and knowledge sharing that caters to the laser and electro-optics communities.

**Fields Represented:**

* Entrepreneurs and Innovators
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Please register for the ICALEO 2023 Conference to join the event.

ICALEO® brings together the brightest minds, seasoned professionals, and pioneering researchers from around the world. With a laser-focused agenda, ICALEO offers an exceptional platform to delve into the cutting-edge advancements, diverse applications, and transformative research that define lasers and electro-optics.

Globally, the supply of electric vehicles is rapidly increasing due to the regulation of CO2 emission. Laser welding is essential for core parts of electric vehicles, and welding of copper (Cu) material accounts for a large proportion. Unstable welding quality can cause fire and threaten the life of the operator. Quality is urgently needed. In-depth research on Cu sheet laser welding is needed. Laser welding for electric vehicle battery uses a lot of copper. However, IR laser is difficult to achieve stable melting and quality control due to the high reflectivity of copper, and the beam penetrates the battery, causing cell damage and fire. In this study, core parts such as cylindrical batteries of electric vehicles are welded using a green laser for stable fusion and quality. In this study, a 2 kW green laser welding system and a 6-axis industrial robot were used. Green laser welding process technology is applied using nickel-coated 0.5 mm copper on the top and 0.5 mm mild steel on the bottom. Optical microscope analysis was used to examine the penetration after green laser welding.&nbsp; The laser welding microstructural modification was investigated using scanning electron microscope(SEM) and energy disperse X-ray spectrometer(EDS). After green laser welding, the result is measured using shear stress test. Moerever, Using Laser welding monitoring system(LWM) the causes of welding defects were identified and the process conditions for welding quality deterioration were matched.

A Study on Green Laser Welding Characteristics of Core Materials for Electric Vehicles

Enhancing the durability of molds, jigs, and tools is crucial for the industry, and one approach to achieve this is by forming a metallic layer with high hardness on their surfaces. Metallic layers with high hardness can be formed through laser metal deposition (LMD), which is one of the additive manufacturing processes, using cemented carbide powder. However, crack initiation typically occurs inside cemented carbide layers formed by the LMD. Therefore, achieving a cladding process for cemented carbide layers without cracks is desired for practical applications. In this study, effects of WC ratios in WC-Co cemented carbide granulated powder on formed bead size and crack initiation during the LMD processing were investigated. The number of cracks generated during the LMD processing was evaluated using an acoustic emission (AE) technique. The number of burst-type AE signals generated was counted as the number of cracks. Seven types of WC-Co cemented carbide granulated powders with WC ratios ranging from 30.5mass% to 92mass% were prepared. Beads were formed using each powder through the LMD, with AE signals being measured. In the case of a WC ratio of 42.9mass% or less, no crack was observed. On the other hand, cracks were observed when the WC ratio was 53.9mass% or greater, and the number of cracks increased with an increase in the WC ratio.

Effects of WC Ratios on Bead Size and Crack Initiation in Forming WC-Co Cemented Carbide by Laser Metal Deposition

Inconel has been used in many industrial components such as a blade of gas turbine because of having its high creep strength and high corrosion resistance. The gas turbine for next generation requires more complex shape to improve the performance. A selective laser melting (SLM) method is one of additive manufacturing (AM) technologies, which is suitable for making metal objects with complex shape rapidly. The AM for metals is a fabrication method that enables direct modeling of three-dimensional (3D) products from a metal powder based on 3D-CAD data. The AM method using a laser as a heat source is classified as selective laser melting (SLM) technology. In SLM, the powder absorbs the laser energy to heat. &nbsp;Then the powder melts and solidifies to form a single layer. Generally, IR lasers with a wavelength of around 1 um are employed in SLM process. Recently, a high-power blue diode laser has been developed.&nbsp; Blue and IR lasers have different light absorption rates for Inconel, which may affect samples fabricated with SLM. 
&nbsp;In this study, 3D fabrication of Inconel was demonstrated by the blue and IR laser, respectively to compare with the process and mechanical property. As a result, high efficiency and fine object was obtained with blue laser.

Comparison with Blue and IR Laser for Inconel Fabrication in Selective Laser Melting

This study reports a laser annealing technique to activate dopants in Si for semiconductor application. In this study, a CW laser of 532 nm was used to anneal the phosphorus (P) doped Si wafer, and the effects of laser power and scan speed on electrical, microstructural and chemical characteristics of the P-doped Si were investigated. It was found that the amorphized Si during the dopant implantation process was successfully recrystallized to either polycrystalline Si or single crystal Si by laser annealing. The sheet resistance decreased with increasing laser power or decreasing scan speed due to the improved crystallinty of Si. The full epitaxial growth of Si was achieved by inducing the complete melting of the amorphized Si, and under the this condition, a minimum sheet resistance was obtained. According to the dopant concentration analysis, it was found that dopant diffusion to the depth direction was very limited. The redistribution of dopants was only generated near the shallow surface region. As a result, relatively uniform concentration of the dopant was achieved, which is advantageous for the formation of the sallow junction. The results of this study show that the potential benefits of the laser annealing technique for improving the properties of semiconductor materials. Further research to explore various characteristics of the laser annealed Si is in progress.

Dopant Activation Annealing of Si Using CW Laser of 532 NM

The processability of pure Inconel X750 and Inconel X750 mixed with 15% vol. of titanium carbide particulate through laser Directed Energy Deposition (l-DED) was evaluated. The powders used had a particle size in a range unusual to l-DED processing (0.18 µm to 24.05 µm), this case study presents the difficulties in processing a thin quadri-modal powder and describes possible measures to mitigate them, while also reporting, likely for the first time, on the l-DED processing of Inconel X750 and such related MMC. The choice in reinforcement particle size and composition aimed for a reduction in material density and insertion of additional reinforcement mechanisms.&nbsp; Both powders used were analysed in an FT4 rheometer and compared to a reference Inconel 625 powder. l-DED was made viable, but results show that the powders tested here represent a lower limit for the rheological properties accepted by usual l-DED systems. A methodology to quantify the stability of a given processing condition is presented and validated, indicating also that low powder flows are recommended when processing powders of this sort. Inconel X750 demonstrated sensibility to oxidation during processing as depletion of Nb and Ti was detected in the deposits. Nor the MMC, nor the pure material cracked or showed excessive porosity. Microstructural characterization of non-heat-treated materials also showed microsegregation of Nb and Ti and a slight degradation of the added particulate.

Processability of Thin-Powdered Inconel X750 and TiC Metal Matrix Composite by Laser-Directed Energy Deposition

Dicing is one of the main processes during the packaging of semiconductors and the fabrication of electronic devices. As the design of semiconductor chips and electronic devices has become more complex over the years, conventional fabrication methods like saw-dicing present limitations regarding precision, flexibility, and quality. In this study, we present an ultrafast laser based dicing technique for cutting epoxy molding compound with fused silica filler of two different sizes of 32 microns and 55 microns. A three-dimensional two-temperature model (3D-TTM) was used to explore a wide range of process parameters of the dicing process with validation from the experiments using a femtosecond laser. The effect of the process parameters on the efficiency and ablation profile was systematically studied. The effect of the fused silica filler size on the heat transfer and ablation behavior was also discussed in detail. One of the key novelties of the presented work is that the 3D-TTM can be used to find the optimal cutting conditions beyond the capability of the experimental setup. In this study, the 3D-TTM was also used to predict the optimal parameters for a picosecond laser of a different beam wavelength. The study shows that finding the optimal parameters using the 3D-TTM is more effective and lower cost than experimental methods. The study also illustrates the unique advantage of the ultrafast laser based dicing method, making it a technique with huge potential in the fabrication of next-generation semiconductor chips and electronic devices.

Application of Ultrafast Laser Dicing in the Semiconductor Packaging Process

Aluminum alloys are increasingly being considered the material of choice in electric vehicle (EV) manufacturing due to their lightweight characteristics. As multi-material manufacturing expands, weld quality monitoring becomes more important because of EVs’ high safety standards. By monitoring the weld quality, inspecting time can be saved and it tends to replace non-destructive testing as well. Proper interface width in overlap joint configuration ensures stable weld strength. Especially, the interface widths are known to directly influence the mechanical properties during interfacial failures. Therefore, predicting the interface width accurately is critical during the welding property monitoring process. In this study, we present a method that is able to predict interfacial width in overlap joint configuration for laser welding of aluminum alloy using sensors and a CNN-based deep learning model. A spectrometer and a CCD camera were attached to the head. The inputs for the multi-input CNN-based deep learning prediction models were spectral signals, represented by light intensity through the spectrometer, and the molten pool's dynamic images filmed by a CCD camera. The output was the interfacial width collected from the cross-sectional analysis. Through this, we show high prediction accuracy in predicting the interfacial width in overlap joint configuration for laser welding of aluminum alloy.

Prediction of the Interface Width in Over Lap Joint Configuration for Laser Welding of Aluminum Alloy Using Sensors

Cars consume a lot of energy to move their own weight. By reducing the thickness of the plates used to build car bodies, without losing ductility, strength and energy absorption after impact, the weight of the vehicle is reduced and, consequently, its energy efficiency is increased. However, one of the biggest problems faced when forming sheet metal to obtain a suitable geometry is the springback effect. In this work, the influence of laser welding parameters on the springback of DP600 two-phase steel sheets was studied, varying parameters such as: the punching speed in the bending test, the initial bending internal angle, and the observation of the springback variation with time. Tensile tests, Vickers hardness and optical microscopy analysis were carried out to correlate the results with the mechanical properties of the material. Laser welding was used to join DP600 steel plates with the weld bead being in the position where the bending occurs. Controlling the springback value ensures better quality in vehicle manufacturing. It is concluded that, by increasing the punch lowering speed, the springback values were increased. However, by increasing the initial internal bend angle from 30 to 90 degrees, the springback values were decreased. It was also verified that by increasing the observation time, the springback variation continued to increase 5 days after the bending test, until stabilization.

The Influence of Laser Welding Parameters on the Springback of DP600 High-Strength Steel Thin Sheets

An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropulos et al, 1995; Iyer et al, 2017]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ~ 0.1 mm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.

A New Thermal Solver for Mitigating Surface Temperature Instability Induced by Laser-Induced Heating

The global mobility and regenerative power revolution is in full swing. Demand for components for electric cars, alternative drives and energy storage is rising continuously. 
At the heart of many solutions is the laser. Especially high power and mid power nanosecond Laser for surface treatment in many different applications. 
Another field to enhance power efficiency is to avoid electrical losses. One main driver of losses in EV’s or high currant cabinets are screwed busbar connections. State of the art solutions to prevent contact resistances losses are expensive environmental critical coating processes with deformable high conductive metals like nickel. Several papers have shown that mechanical pretreatment of the busbar surface in the interaction zone of screwed joining can lead to a significant drop down of the contact resistance. In our investigation we show that Laser surface treatment is an ideal tool to transfer these results in a highly flexible and productive way. 
We will demonstrate with an industrial relevant case study the potential to significantly decrease the contact resistance on screwed connections of copper busbars by means of laser surface treatment. 
Therefore, 3 different Laser sources, different treatment strategies were performed. All busbars were screwed and electrically qualified by a calibrated µ-Ohmmeter. The investigation leads to the conclusion, that a tailored laser surface treatment combines highest productivity, lowest contact resistance without any additional coating steps, a long shelf lifetime and highest reproducibility.

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Water and Oil Wettability Customization by Tailoring Micro-Structured Polymers

Next from ICALEO 2023

A Study on Green Laser Welding Characteristics of Core Materials for Electric Vehicles