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118 results on '"Kotz-Helmer, Frederik"'

3. A review of materials used in tomographic volumetric additive manufacturing

Author

Madrid-Wolff, Jorge, Toombs, Joseph, Rizzo, Riccardo, Bernal, Paulina Nuñez, Porcincula, Dominique, Walton, Rebecca, Wang, Bin, Kotz-Helmer, Frederik, Yang, Yi, Kaplan, David, Zhang, Yu Shrike, Zenobi-Wong, Marcy, McLeod, Robert R., Rapp, Bastian, Schwartz, Johanna, Shusteff, Maxim, Talyor, Hayden, Levato, Riccardo, and Moser, Christophe

Published
2023
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4. Volumetric Additive Manufacturing of Silica Glass with Microscale Computed Axial Lithography

Author

Toombs, Joseph, Luitz, Manuel, Cook, Caitlyn, Jenne, Sophie, Li, Chi Chung, Rapp, Bastian, Kotz-Helmer, Frederik, and Taylor, Hayden

Subjects
Physics - Applied Physics
Abstract

Glass is increasingly desired as a material for manufacturing complex microscopic geometries, from the micro-optics in compact consumer products to microfluidic systems for chemical synthesis and biological analyses. As the size, geometric, surface roughness, and mechanical strength requirements of glass evolve, conventional processing methods are challenged. We introduce microscale computed axial lithography (micro-CAL) of fused silica components, by tomographically illuminating a photopolymer-silica nanocomposite which is then sintered. We fabricated 3D microfluidics with internal diameters of 150 micrometers, freeform micro-optical elements with surface roughness of 6 nm, and complex high-strength trusses and lattice structures with minimum feature sizes of 50 micrometers. As a high-speed, layer-free digital light manufacturing process, micro-CAL can process extremely viscous nanocomposites with high geometric freedom, enabling new device structures and applications.

Published
2021
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9. Scanning‐Laser‐Based Microstereolithography of Microfluidic Chips with Micron Resolution.

Author

Rein, Christof, Kamranikia, Keynaz, Council, Raymonde, Pezeshkpour, Pegah, Kotz‐Helmer, Frederik, and Rapp, Bastian E.

Subjects
RAPID prototyping, THREE-dimensional printing, SOFT lithography, ETHYLENE glycol, MICROFLUIDICS, MICROFLUIDIC devices, STEREOLITHOGRAPHY
Abstract

The constant improvement of stereolithography (SL) in terms of achievable resolution and printing time has sparked high expectations that SL will enable the rapid prototyping of truly microfluidic chips with features below 100 µm. However, most commercial high‐resolution stereolithography devices are based on Digital Light Processing (DLP) and thus sacrifice lateral printing size for resolution. Consequently, even 10 years after the advent of microstereolithography there is no commercialized 3D printing system that can effectively fulfill all the demands to replace soft lithography for microfluidic prototyping. In this work, for the first time, This study demonstrates that a commercial laser‐based stereolithography device is capable of manufacturing microfluidic chips with embedded channels smaller than 100 µm with a footprint of 7.24 × 0.3 cm2. A chip fabricated in poly(ethylene glycol) diacrylate (PEGDA) that can readily be used for fluid mixing, is presented in this study. This research shows that the accessibility of high‐resolution chips with footprints of several cm2, using laser‐based stereolithography, enables the manufacturing of truly microfluidic systems with high impact on prototyping and manufacturing. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Sub‐Micron Replication of Fused Silica Glass and Amorphous Metals for Tool‐Based Manufacturing.

Author

Kluck, Sebastian, Prediger, Richard, Hambitzer, Leonhard, Nekoonam, Niloofar, Dreher, Franziska, Luitz, Manuel, Lunzer, Markus, Worgull, Matthias, Schneider, Marc, Rapp, Bastian E., and Kotz‐Helmer, Frederik

Subjects
METALLIC glasses, FUSED silica, MASS production, INJECTION molding, METAL castings
Abstract

The growing importance of submicrometer‐structured surfaces across a variety of different fields has driven progress in light manipulation, color diversity, water‐repellency, and functional enhancements. To enable mass production, processes like hot‐embossing (HE), roll‐to‐roll replication (R2R), and injection molding (IM) are essential due to their precision and material flexibility. However, these processes are tool‐based manufacturing (TBM) techniques requiring metal molds, which are time‐consuming and expensive to manufacture, as they mostly rely on galvanoforming using templates made via precision microlithography or two‐photon‐polymerization (2PP). In this work, a novel approach is demonstrated to replicate amorphous metals from fused silica glass, derived from additive manufacturing and structured using hot embossing and casting, enabling the fabrication of metal insets with features in the range of 300 nm and a surface roughness of below 10 nm. By partially crystallizing the amorphous metal, during the replication process, the insets gain a high hardness of up to 800 HV. The metal molds are successfully used in polymer injection molding using different polymers including polystyrene (PS) and polyethylene (PE) as well as glass nanocomposites. This work is of significant importance to the field as it provides a production method for the increasing demand for sub‐micron‐structured tooling in the area of polymer replication while substantially reducing their cost of production. [ABSTRACT FROM AUTHOR]

Published
2024
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21. High‐Resolution Patterning of Organic–Inorganic Photoresins for Tungsten and Tungsten Carbide Microstructures

Author

Luitz, Manuel, primary, Pellegrini, Diana, additional, von Holst, Miriam, additional, Seteiz, Khaled, additional, Gröner, Lukas, additional, Schleyer, Mario, additional, Daub, Michael, additional, Warmbold, Andreas, additional, Thomann, Yi, additional, Thomann, Ralf, additional, Kotz-Helmer, Frederik, additional, and Rapp, Bastian E., additional

Published
2023
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25. 3d Printed Elastic Fluoropolymer with High Stretchability and Enhanced Chemical Resistance for Microfluidic Applications

Author

Song, Qingchuan, primary, Hamza, Ahmed, additional, Li, Chengzhi, additional, Sedeky, Abanoub S., additional, Chen, Yunong, additional, Zhu, Mingshen, additional, Goralczyk, Andreas, additional, Mayoussi, Fadoua, additional, Zhu, Pang, additional, Hou, Peilong, additional, Piesold, Christian, additional, Helmer, Dorothea, additional, Rapp, Bastian E., additional, and Kotz-Helmer, Frederik, additional

Published
2023
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26. High-resolution patterning of organic-inorganic photoresins for tungsten and tungsten carbide microstructures

Author

Luitz, Manuel, Pellegrini, Diana, Holst, Miriam von, Seteiz, Khaled, Gröner, Lukas, Schleyer, Mario, Daub, Michael, Warmbold, Andreas, Thomann, Yi, Thomann, Ralf, Kotz-Helmer, Frederik, Rapp, Bastian E., and Publica

Subjects
two-photon polymerization, carbothermal reduction, tungsten, metal printing, microstructuring, tungsten carbide
Abstract

Tungsten is an important material for high-temperature applications due to its high chemical and thermal stability. Its carbide, that is, tungsten carbide, is used in tool manufacturing because of its outstanding hardness and as a catalyst scaffold due to its morphology and large surface area. However, microstructuring, especially high-resolution 3D microstructuring of both materials, is a complex and challenging process which suffers from slow speeds and requires expensive specialized equipment. Traditional subtractive machining methods, for example, milling, are often not feasible because of the hardness and brittleness of the materials. Commonly, tungsten and tungsten carbide are manufactured by powder metallurgy. However, these methods are very limited in the complexity and resolution of the produced components. Herein, tungsten ion-containing organic–inorganic photoresins, which are patterned by two-photon lithography (TPL) at micrometer resolution, are introduced. The printed structures are converted to tungsten or tungsten carbide by thermal debinding and reduction of the precursor or carbothermal reduction reaction, respectively. Using TPL, complex 3D tungsten and tungsten carbide structures are prepared with a resolution down to 2 and 7 μm, respectively. This new pathway of structuring tungsten and its carbide facilitates a broad range of applications from micromachining to metamaterials and catalysis.

Published
2023

29. Injection Molding of Magnesium Aluminate Spinel Nanocomposites for High‐Throughput Manufacturing of Transparent Ceramics

Author

Mader, Markus, primary, Prediger, Richard, additional, Schell, Karl G., additional, Schmidt, Gabriela, additional, Dorn, Alex, additional, Jenne, Sophie, additional, Kluck, Sebastian, additional, Hambitzer, Leonhard, additional, Luitz, Manuel, additional, Schwarz, Claudia, additional, Milich, Marcel, additional, Greiner, Christian, additional, Rapp, Bastian E., additional, and Kotz‐Helmer, Frederik, additional

Published
2022
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31. Contributors

Author

Chen, Qiang, Cooperstein, Ido, Dohmen, Mike, Dudukovic, Nikola, Dylla-Spears, Rebecca, Farrell, Efrat Shukrun, Fears, Tyler, Geiß, Marco, Graniel, Octavio, Ha, Jungmin, Heinrich, Andreas, Hellmann, Ralf, Helmer, D., Ilhan, Murat-Jakub, Kinzel, E.C., Kotz-Helmer, Frederik, Magdassi, Shlomo, Muñoz-Rojas, David, Nguyen, Du T., Orzol, Dominik Karl, Pané, Salvador, Prediger, Richard, Puigmartí-Luis, Josep, Rapp, Bastian E., Roos, Christian, Sasan, Koroush, Schwarz, Simon, Sevim, Semih, Sorrenti, Alessandro, Walton, Rebecca, Yee, Timothy D., and Zheng, Kai

Published
2025
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34. Spray‐Coating of Superhydrophobic Coatings for Advanced Applications.

Author

Goralczyk, Andreas, Savicheva, Sofya, Montazeri, Ramin, Fine, Simona, Mayoussi, Fadoua, Zhu, Pang, Steffen, Kay, Kotz-Helmer, Frederik, Helmer, Dorothea, and Rapp, Bastian E.

Subjects
SURFACE coatings, MEMBRANE separation, POROUS materials, THERMAL resistance, PHOTOPOLYMERIZATION
Abstract

Superhydrophobic coatings are widely applicable, e.g., as self‐cleaning surfaces or water–oil separation membranes, yet their wider usage is impeded due to costs of fabrication, size, or substrate limitation. Spray‐coating is a versatile coating procedures and might offer a good solution for the fabrication of these superhydrophobic coatings, due to the fact that coatings can be fabricated on various materials in a simple, fast, and inexpensive manner. Most procedures rely on hybrid coatings of hydrophobized nanoparticles and a polymeric matrix, which have several drawbacks including the easy loss of nanoparticles and difficult waste handling. Here, the fabrication of the superhydrophobic material, called Fluoropor, for the first time, by spray‐coating on various substrates including metals, tissues, concrete, and glass is presented. It is fabricated by spray‐coating a mixture of a highly fluorinated monomer blended with porogens followed by photopolymerization. The superhydrophobicity of the material relies on the porous structure on the micro‐/nanoscale across the bulk material and does not require any nanoparticles. Excellent self‐cleaning ability of these coatings, resistance against thermal and abrasive impact, and their application as oil–water separation membranes are shown. This versatile applicability is highly promising for real‐world application as self‐cleaning coatings or oil–water separating membranes. [ABSTRACT FROM AUTHOR]

Published
2023
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35. A Polystyrene Photoresin for Direct Lithography of Microfluidic Chips

Author

Franco Corredor, Santiago, primary, Mayoussi, Fadoua, additional, Luitz, Manuel, additional, Kick, Andrea, additional, Goralczyk, Andreas, additional, Böcherer, David, additional, Vera, Grace, additional, Helmer, Dorothea, additional, Kotz‐Helmer, Frederik, additional, and Rapp, Bastian E., additional

Published
2022
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37. On‐chip Liquid Metal Plug Generator

Author

Bhagwat, Sagar, primary, O'Brien, Ciarán, additional, Hamza, Ahmed, additional, Sharma, Shatakshi, additional, Rein, Christof, additional, Sanjaya, Mario, additional, Helmer, Dorothea, additional, Kotz‐Helmer, Frederik, additional, Pezeshkpour, Pegah, additional, and Rapp, Bastian E., additional

Published
2022
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42. Fused Deposition Modeling of Microfluidic Chips in Transparent Polystyrene

Author

Mader, Markus, Rein, Christof, Konrat, Eveline, Meermeyer, Sophia Lena, Lee-Thedieck, Cornelia, Kotz-Helmer, Frederik, Rapp, Bastian E., Mader, Markus, Rein, Christof, Konrat, Eveline, Meermeyer, Sophia Lena, Lee-Thedieck, Cornelia, Kotz-Helmer, Frederik, and Rapp, Bastian E.

Abstract

Polystyrene (PS) is one of the most commonly used thermoplastic materials worldwide and plays a ubiquitous role in today’s biomedical and life science industry and research. The main advantage of PS lies in its facile processability, its excellent optical and mechanical properties, as well as its biocompatibility. However, PS is only rarely used in microfluidic prototyping, since the structuring of PS is mainly performed using industrial-scale replication processes. So far, microfluidic chips in PS have not been accessible to rapid prototyping via 3D printing. In this work, we present, for the first time, 3D printing of transparent PS using fused deposition modeling (FDM). We present FDM printing of transparent PS microfluidic channels with dimensions as small as 300 µm and a high transparency in the region of interest. Furthermore, we demonstrate the fabrication of functional chips such as Tesla-mixer and mixer cascades. Cell culture experiments showed a high cell viability during seven days of culturing, as well as enabling cell adhesion and proliferation. With the aid of this new PS prototyping method, the development of future biomedical microfluidic chips will be significantly accelerated, as it enables using PS from the early academic prototyping all the way to industrial-scale mass replication.

Published
2021

43. In SituActuators with Gallium Liquid Metal Alloys and Polypyrrole-Coated Electrodes

Author

Bhagwat, Sagar, Goralczyk, Andreas, Luitz, Manuel, Sharieff, Lathif, Kluck, Sebastian, Hamza, Ahmed, Nekoonam, Niloofar, Kotz-Helmer, Frederik, Pezeshkpour, Pegah, and Rapp, Bastian E.

Abstract

Gallium liquid metal alloys (GLMAs) such as Galinstan and gallium–indium eutectic (EGaIn) are interesting materials due to their high surface tensions, low viscosities, and electrical conductivities comparable to classical solid metals. They have been used for applications in microelectromechanical systems (MEMS) and, more recently, liquid metal microfluidics (LMMF) for setting up devices like actuators. However, their high tendency to alloy with the most common metals used for electrodes such as gold (Au), platinum (Pt), titanium (Ti), nickel (Ni), and tungsten–titanium (WTi) is a major problem limiting the scaleup and applicability, e.g., liquid metal actuators. Stable electrodes are key elements for many applications and thus, the lack of an electrode material compatible with GLMAs is detrimental for many potential application scenarios. In this work, we study the effect of actuating Galinstan on various solid metal electrodes and present an electrode protection methodology that, first, prevents alloying and, second, prevents electrode corrosion. We demonstrate reproducible actuation of GLMA segments in LMMF, showcasing the stability of the proposed protective coating. We investigated a range of electrode materials including Au, Pt, Ti, Ni, and WTi, all in aqueous environments, and present the resulting corrosion/alloying effects by studying the interface morphology. Our proposed protective coating is based on a simple method to electrodeposit electrically conductive polypyrrole (PPy) on the electrodes to provide a conductive alloying-barrier layer for applications involving direct contact between GLMAs and electrodes. We demonstrate the versatility of this approach by direct three-dimensional (3D) printing of a 500 μm microfluidic chip on a set of electrodes onto which PPy is electrodeposited in situfor actuation of Galinstan plugs. The developed protection protocol will provide a generic, widely applicable strategy to protect a wide range of electrodes from alloying and corrosion and thus form a key element in future applications of GLMAs.

Published
2023
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