United States

Laser bioprinting techniques are emerging as an ideal tool for cell printing due to their excellent cell viability, close to 100%, and high spatial resolution. In this paper, we discuss a special adaptation of the Blister-Actuated Laser Induced Forward Transfer (BA-LIFT) technique for cell printing, performed at the Laser Center UPM. BA-LIFT is a well-known laser direct writing technique and has been used for biological material transfer before. However, in our case we use a thick polyimide layer (30 microns) for blister generation, which provides exceptional protection of the cells from the incoming laser beam. Due to the transparency of this material in the VIS range, we can implement both fluorescence and conventional vision systems coaxial with the laser path to identify the cells to be transferred, opening up the possibility of cell sorting and even cell survival tracking in both donor and acceptor substrates. Negative and positive selection of cells is possible with this setup, with the possibility of leaving the cells to be transferred completely unaltered in the case of negative selection. &amp;nbsp;We present some recent applications of this technique developed in our laboratory, including single-cell isolation for single-cell sequencing in translational medical applications and current studies for applications in tissue engineering. In addition, we present a high-speed imaging study of the transfer process to discuss the dynamics of jet generation and cell deposition mechanisms in the acceptor substrate using our approach.

ICALEO 2023

Laser Bioprinting Using BA-LIFT: From Single Cell Isolation to Tissue Engineering

tisuue engineering

single cell isolation

blister actuated laser induced forward transfer

laser bioprinting

Laser bioprinting techniques are emerging as an ideal tool for cell printing due to their excellent cell viability, close to 100%, and high spatial resolution. In this paper, we discuss a special adaptation of the Blister-Actuated Laser Induced Forward Transfer (BA-LIFT) technique for cell printing, performed at the Laser Center UPM. BA-LIFT is a well-known laser direct writing technique and has been used for biological material transfer before. However, in our case we use a thick polyimide layer (30 microns) for blister generation, which provides exceptional protection of the cells from the incoming laser beam. Due to the transparency of this material in the VIS range, we can implement both fluorescence and conventional vision systems coaxial with the laser path to identify the cells to be transferred, opening up the possibility of cell sorting and even cell survival tracking in both donor and acceptor substrates. Negative and positive selection of cells is possible with this setup, with the possibility of leaving the cells to be transferred completely unaltered in the case of negative selection. &nbsp;We present some recent applications of this technique developed in our laboratory, including single-cell isolation for single-cell sequencing in translational medical applications and current studies for applications in tissue engineering. In addition, we present a high-speed imaging study of the transfer process to discuss the dynamics of jet generation and cell deposition mechanisms in the acceptor substrate using our approach.

technical paper

**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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* Students and Graduates
* Policy Makers and Regulators
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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.

Ultra-fast Beam Shaping Using Coherent Beam Combining

While conventional vehicle design disciplines such as car body design are established, electromobility-specific disciplines are in the technological orientation and ramp-up phase. 
In particular, the demand for components like batteries, e-motors and power electronics is growing continuously. Aluminum alloys are chosen for parts like casted power electronics housings and heat exchangers made of sheet metal or extrusion profiles. Next to the material-specific challenges and mentioned requirements, the focus is on the gas-tight welding of the aluminum alloys. 
This paper offers an insight into the requirements of these parts as well as the innovative optics approach with a novel MultiFocus solution and multi core fiber technologies. The material-specific challenges, especially for helium-tight welding of aluminum casted housings with forging alloys are characterized. This analysis is conducted using gas-tightness measurements, CT-scans, micrographs and high-speed recordings in order to elaborate the fundamental laser-material-process interdependencies and the correlation between process and resulting quality in terms of tightness. 
Furthermore, high speed synchrotron recordings are conducted at the DESY and based on that a detailed evaluation of the laser and material interaction is conducted. This allows an explanation of the interactions for the prevention of pore formation in aluminum alloys and thus the characterization of the boundary conditions for a reliable process of gas-tight welding on aluminum alloys.

Welding of Cast Aluminum Alloys for Power Electronics: In-Situ Synchrotron X-Ray Analysis of Different Laser Beam Shaping Technologies for the Prevention of Defects

Brass represents a large part in the production of components within the copper alloy group. Laser beam welding of this alloy offers great potential for many applications in terms of achievable seam quality and productivity. However, there is a very high tendency of the process to produce irregular seam surfaces, ejection of the molten metal and pore formation. These are due, among other things, to instabilities of the keyhole, which is favored by the evaporation of the alloy component zinc. Furthermore, near-infrared laser beam wavelength can couple poorly into the material due to the low absorption level of brass, whereas absorption jumps during the melt transition. In recent years, high-brilliance near-infrared laser beam sources with adjustable beam profiles have been developed that can lead to keyhole stabilization. 
The experimental process investigations are on deep penetration welding of different brass alloys (CuZn37 and CuZn39Pb3). A multi-kW laser beam source with combined core and ring beam is used for this purpose. Main process parameters are identified and systematically varied. The produced seams are analyzed and evaluated using different methods (including micrograph analysis and topography images). The results are correlated with the process parameters. Line Energy per unit length, spot size and process gas supply have a significant effect on the weld seam resulting. Process parameters were found to produce high quality bead on plate and butt welds for sheet thicknesses of 2 mm.

Laser Beam Welding of Brass With Combined Core and Ring Beam

Fast oscillation of the laser beam is an established and proven method for beam shaping to improve laser material processing in terms of machining quality, process stability, and time. In the first part, an overview will be given for available and already proven oscillation devices as 
well as equipment under development. Solutions for beam oscillations in x and y direction as well as solutions for oscillations of the focal plane along the beam propagation direction (z direction) are introduced. Advantages and disadvantages of the various concepts are considered and 
evaluated. 
In the second part, examples will be provided to demonstrate the profitable use of fast laser beam oscillations for the applications of cutting, welding, hardening, and cladding. Finally, opportunities of 3D beam shaping provided by oscillating the beam focus in three spatial directions 
simultaneously or opportunities utilizing x/y oscillations of the laser focal point like a jigsaw are discussed. Consideration is given to whether beam oscillations have the potential to eliminate the need for ever higher laser powers or different wavelength.

Fast Beam Oscillations Improve Laser Material Processing

Automotive lamps have not only functional roles but have highly aesthetic purposes in the design of a car. As such, they use complex three-dimensional shapes to implement various designs. The main manufacturing challenge comes from the plastic bonding process of the complex components which currently is done by thermal bonding, ultrasonic bonding, and laser welding. Laser welding processes with a narrow joint area are preferred since they require minimal joint area and produce no burr. In this study, an optimization study for simultaneous bonding of lamps is carried out using multiple light sources generated by connecting specially manufactured bundle optical fibers with a diode laser source. The diode laser beams with a wavelength of 915 nm and a power of 80 W, each, were simultaneously delivered through a 30-optical fibers bundle. The fibers were integrated within the mold that holds the lamp achieving transmission welding through the overlapped upper transparent polymer PMMA (IF850) and the lower nontransparent polymer ABS (HL121H). The process parameters investigated were the laser power, duration time, waveguide gap, and clamping pressure. We present optimized process parameters that achieved no pores and relatively uniform melting. In the shear test, the average load was approximately 1300 N, and the base sheet fractures along the welding joints were observed.

Experimental Evaluation of PMMA-ABS Transmission Welding Using Mold-Integrated Simultaneous Laser Welding Technology

Endless carbon-fibre reinforced plastics (CFRP) are important lightweight construction materials. While the majority contains a thermoset matrix material, latest developments see an increase of CFRP with a thermoplastic matrix (CFRTP). This is due to their enhanced machinability and versatile material characteristics. However, high-performance thermoplastics and endless carbon fibres are both expensive resources. During the production of parts made from CFRTP, scrap-pieces and left-overs from the cutting process are usually disposed of. To increase the resource efficiency, a process is developed that includes the autonomous laser cutting of such CFRTP remnants to chips of unified dimensions, which can then be reused in the production of long-fibre reinforced CFRTP laminates. 
This study focuses on the laser process development for the cutting of CFRTP with a polyether ether ketone (PEEK) matrix. The development aims for short processing times and minimum thermal alteration of the PEEK. Laser cutting of semi-finished CFRTP is especially challenging, because although most fibres within a carbon fibre roving might be cut, individual fibres might still be intact and may cause fibre pull-out that would severely reduce the cutting-edge’s quality. Therefore, to verify that the CFRTP was completely cut, an optical process monitoring system is developed. 
In this investigation, process parameters are evaluated in terms of cutting time, surface appearance, and the completeness of the cuts. Surface analysis shows colour changes of the PEEK on an area of less than 1mm from the cutting edge. The monitoring system for cut completeness was introduced and showed good detection results.

Laser Cutting of Semi-finished CFRTP Products for Better Resource Efficiency

Glass materials with higher indices of refraction are being developed for use in augmented reality (AR) and similar immersive reality eyewear.&nbsp; Benefits such as lighter weight, larger/better display, and reduced power consumption are being realized through the development of new types of glass having refractive indices above 1.7 and approaching 2.0.&nbsp; As the AR eyewear market continues to grow, there is a growing need to cut these materials with good quality and at high throughputs.&nbsp; AR glass materials present additional challenges for kerf-less laser cutting, as these methods depend on the propagation of light through the bulk of the material which can be impacted both by the material index as well as any coatings present on the glass surfaces.&nbsp; In this work we demonstrate the use of tailored picosecond infrared (IR) pulse bursts to improve the quality of high-throughput Bessel beam-based glass cutting processes, with noteworthy results including roughness improvements of ~40%, overall throughputs in the meters-per-second regime, and cutting of corner radiuses as small as 500 µm.&nbsp; Furthermore, because AR eyewear incorporates active glass for image projection, various glass surface coatings need to be applied.&nbsp; As such, we also present cutting results with the Bessel beam passing through a slit aperture located proximal to the glass surface, which represents processing through an opened channel in such coatings.

Cutting High-Index of Refraction AR Glass with Tailored ps IR Pulse Bursts and Surface-Proximal Slit-Apertured Bessel Beams

In today’s manufacturing, additive manufacturing processes enable the production of complicated three dimensional structures that are hard to be manufactured with traditional manufacturing processes. Due to its high build rate, the Directed Energy Deposition (DED) process is an attractive and versatile process to manufacture these kind of components. In addition to the production of components, DED is used for repair or coating applications. The DED process consists of a multitude of complex thermal mechanisms with high heating and cooling rates of 103 up to 105 K/s. For materials with a high hardness or a low thermal conductivity like tool steels, cast iron or tungsten carbide these high cooling rates can lead to defects in the microstructure like cracks, pores or delamination between the substrate and the deposited structures. By preheating the substrate, the cooling rates can be reduced, and defects can be eliminated. In this paper a preheating cycle was developed, which uses the laser of an DMG MORI LT 65 DED hybrid machine as a moving heat source for the substrate preheating. For this cycle, process parameters, a tool path strategy and a temperature control system were developed. The impact of the elaborated concept was shown by welding tungsten carbide in nickel matrix on S235 steel substrate.

Development of a Laser Preheating Concept for Directed Energy Deposition

This paper provides quantitative information about the paths taken by powder particles which do not enter the laser generated melt pool during laser cladding (DED). These wasted powder particles bounce off the melt pool and the surrounding solid areas. This wastage reduces the productivity of the process. In this paper specially developed software was used to analyze High Speed Imaging videos of the cladding process, to monitor the directions of powder particle flight away from the melt pool area. This information has been correlated to the geometry of the melt pool zone for three different cladding techniques; single track cladding (A tracks), standard overlapping track cladding (AAA cladding) and a recently developed technique called ABA cladding. The results show that the melt pool geometry has a strong influence on powder catchment efficiency and the trajectories of powder particles which bounce away from the laser-material interaction area. ABA cladding was found to have considerably better powder catchment efficiency than standard AAA cladding and this improvement can explained by consideration of the geometries of the melt pools and surrounding solid material in each case. As powder costs are an important factor in industrial laser cladding, the adaption of the ABA technique could have a beneficial effect on the profitability of the process

Laser Cladding (DED); A High-Speed-Imaging Examination of Powder Catchment Efficiency as a Function of Melt Pool Geometry

With recent technological advances in additive manufacturing, laser-directed energy deposition (L-DED) is frequently chosen as a manufacturing process of Inconel 718 (IN718), which is a precipitation hardening alloy that exhibits excellent mechanical properties at elevated temperature after various heat treatments. However, undesirable recrystallization occurs during the post-heat treatment, resulting in the growth of equiaxed grains, which offset the advantage of columnar grain structure from the layer-by-layer deposition. Induction heating-assisted L-DED, which uses induction heating during the deposition, has the potential to skip the first step of the heat treatment by maintaining the deposit temperature at the heat treatment temperature. In this study, three cube-shaped IN718 were deposited using the induction heating-assisted L-DED system at the holding temperature of homogenization, solution, aging heat treatment, respectively. The temperature conditions were selected according to the standard heat treatment specification of IN718 product. In the induction heating-assisted L-DED, microstructure of the deposits strongly depends on the holding temperature of induction heating during deposition. For each deposit,&nbsp;the secondary phases were analyzed by using a scanning electron microscope and the grain structures were studied using electron backscattered diffraction. Additionally, the mechanical properties of each deposit were evaluated. The results of this study can provide the guide for selecting the proper holding temperature during the induction heating-assisted L-DED to achieve the desired microstructure and mechanical properties.

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Laser Bioprinting Using BA-LIFT: From Single Cell Isolation to Tissue Engineering

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Ultra-fast Beam Shaping Using Coherent Beam Combining