Additive manufacturing (AM) is transforming how we shape matter—but more fundamentally, how materials must be designed. Under laser-driven, far-from-equilibrium conditions, material properties do not simply persist; they emerge during processing. Energy input, thermal history, and interaction time become intrinsic components of material behavior. This shift challenges the traditional paradigm of materials science. The goal is no longer to select materials that tolerate additive manufacturing, but to design materials that actively enable it. In the research line Materials for Additive Manufacturing, we develop nano-functionalized feedstock materials tailored to laser-based processes. Our approach follows the concept of nano-integration, where nanoparticles are deliberately introduced into polymer, metal, ceramic, and bio-based feedstocks to control process–material interactions.

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By modifying surface chemistry, energy absorption, and interfacial behavior, these materials enable improved process stability, expanded processing windows, and tailored microstructures. Rather than acting as passive additives, nanoparticles serve as active process modifiers that link material design directly to laser–matter interaction.

1) Metals (for L-PBF, DED and laser writing)

In metal additive manufacturing, our research focuses on tailoring powder feedstocks via nanoparticle surface functionalization to control microstructure formation under rapid melting and solidification conditions.

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We demonstrate that even sub-monolayer nanoparticle coatings fundamentally alter melt dynamics and solidification pathways. Depending on their physicochemical properties, nanoparticles act either as transient alloying elements or as stable nucleation sites, enabling grain refinement, homogenization, and defect mitigation. For example, low-melting metallic nanoparticles, such as Ag, form transient liquid phases during processing, thereby improving packing density and modifying grain boundary formation [1], whereas refractory nanoparticles, such as ZrB₂, remain solid and act as heterogeneous nucleation sites, promoting fine and uniform grain structures [2]. Similar effects are observed for carbide nanoparticle additivation in aluminum alloys, where grain refinement and improved corrosion behavior are achieved [3]. Beyond structural materials, this concept is extended to functional systems such as permanent magnets within the framework of the CRC/TRR 270 “Hysteresis Design of Magnetic Materials for Efficient Energy Conversion”.  Here, nanoparticle-modified Nd–Fe–B feedstocks enable control over microstructure evolution under additive manufacturing conditions, addressing key limitations such as inhomogeneous grain growth and phase instability [1,4]. The approach highlights that feedstock design must be considered as an integral part of the process chain rather than a fixed input.

In parallel, we develop in-situ diagnostic approaches to directly monitor material behavior during processing, thereby transferring key concepts from the first funding phase of the CRC/TRR 270 into application-oriented process environments. By integrating optical emission spectroscopy into PBF-LB/M systems in collaboration with Aconity3D GmbH, we enable spatially and temporally resolved chemical analysis of the melt pool, providing a pathway toward real-time composition control and digital twins of additive manufacturing processes [5,6]. Complementary to powder-based approaches, we explore micro-laser-sintering strategies for functional materials. In this context, shape-memory alloys have been processed with a particular focus on bio-applications, exemplified by additively manufactured NiTi actuators [7]. These systems highlight the potential of combining functional material behavior with additive manufacturing and can be understood as a step toward 4D additive manufacturing, where material response becomes an integral part of the design.

2) Polymers (for L-PBF and SLA)

In polymer-based additive manufacturing, our research focuses on the design of nano-functionalized feedstock materials for laser powder bed fusion (L-PBF) and photopolymer-based processes.

A central limitation in polymer L-PBF is the insufficient absorption of many technically relevant polymers in the near-infrared (NIR) wavelength range of industrial laser systems. As a result, energy coupling into the material is often inefficient or entirely inhibited, restricting the accessible material portfolio. To overcome this limitation, we employ nano-integration strategies that enable controlled energy absorption directly at the particle surface. By introducing tailored nanoparticle systems, new absorption pathways are created, allowing stable and efficient laser–matter interaction in otherwise weakly absorbing polymer systems.

The modification of polymer powders by nanoparticle additives further enables the tuning of processability and resulting part properties. To avoid agglomeration of nanofillers, we developed a wet impregnation approach in which surfactant-free, laser-generated colloidal nanoparticles are adsorbed onto the surface of polymer particles. This method yields micropowders decorated with highly dispersed nanoparticles and ensures homogeneous surface functionalization. [8, 9, 10] Based on this approach, polymer powders such as thermoplastic polyurethane (TPU) and polyamide 12 (PA12) are functionalized with metal, metal-oxide, -sulfide, and -boride nanoparticles and processed via L-PBF. In this context, nanoparticles act as true process enablers by facilitating NIR absorption, improving melting behavior, and stabilizing the process window. [8,9]

To support the transfer of these material concepts into process design, digital tools developed within the DFG priority programme “Materials for Additive Manufacturing” (SPP2122) enable rapid estimation of process windows and temperature evolution based on material-specific input parameters, thereby linking feedstock design directly to laser–matter interaction and processing conditions.

For photopolymer-based processes such as stereolithography (SLA), nano-integration provides complementary functionality. By incorporating plasmonic nanoparticles, such as gold, into resin systems, the optical response of photopolymers can be tailored, including the replacement of conventional photoinitiators and the controlled tuning of curing behavior [11].

3) Robustness of Additive Manufacturing and Nanoparticle-Loaded AM

Robustness and reproducibility in additive manufacturing cannot be understood as a purely process-related problem. Despite increasingly sophisticated machine control, significant variations in part properties persist across different systems and laboratories. This reflects a fundamental mismatch: while processing technologies have advanced rapidly, feedstock materials have not been designed for the specific conditions of laser-driven manufacturing.

Addressing this imbalance requires a shift in perspective—from adapting processes to existing powders toward designing materials for the process itself. This materials-first paradigm forms the foundation of the DFG Priority Programme SPP 2122 “MATframe”, in which feedstock properties are systematically linked to laser–matter interaction and resulting part performance. Within this framework, the interlaboratory study (ILS) [12] was conceived not as a benchmarking exercise, but as a controlled, cross-institutional experiment to uncover causal relationships along the entire process chain—from powders to processing to parts. Identical polymer and metal feedstocks, including nanoparticle-functionalized systems, were processed across multiple research groups under harmonized conditions and standardized protocols. The study reveals that variability in additive manufacturing originates to a large extent from material-related factors, including particle morphology, surface chemistry, and powder handling. Crucially, it demonstrates that these effects cannot be isolated within individual experiments but require statistically robust, cross-platform analysis to be understood. Nanoparticle-functionalized feedstocks play a central role in this context. Rather than acting as simple additives, they provide a controlled means to modify laser–material interaction, enabling systematic investigation of energy coupling, heat flow, and solidification dynamics. This makes them both a design tool and a model system to probe the governing mechanisms of additive manufacturing [12]. By combining standardized experiments (as detailed in Standard Operating Procedures [13]), open-access data generation [14], and advanced data analysis, the ILS [12] establishes a framework in which material design, process parameters, and part properties can be quantitatively linked. In doing so, it transforms additive manufacturing from an empirical, parameter-driven technology into a materials-based, data-driven discipline, providing the foundation for reproducibility, transferability, and future standardization. These developments are further reflected in dedicated peer-reviewed special issues initiated within the programme, including Materials for Laser Additive Manufacturing in Materials & Design and Materials for Additive Manufacturing in Advanced Engineering Materials, which collectively highlight the growing emphasis on materials-centered approaches in the field.

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4) Ceramics / Semiconductors (for L-PBF)

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In this research line, we work on the off-resonant near-field enhancement of ceramic powders by plasmonic nanoparticles. We show that gold nanoparticles adsorbed on crystalline zinc oxide significantly increase the energy efficiency of infrared laser sintering. At the same time, the plasmonic antennas are embedded into the manufactured part´s oxide matrix. In this way, the enhanced laser sintering process with ligand-free nanoparticles gives access to metal–semiconductor hybrid materials with potential application in light harvesting or energy conversion [15].

5) Biomaterials/Bioinks (for Bioextrusion and Bioprinting)

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In the field of biomaterials, bioextrusion of alginates is an AM process known to be compatible to cell-laden biofabrication. Nanoparticle-filled, thin-walled alginate tubes are printed, measuring several centimeters in length. Nanoparticle doping is achieved in the feedstock printing ink, with particles homogeneously distributed in the 3D part [16]. The embedding of iron nanoparticles showed quite beneficial properties for endothelialisation of the nano-doped alginate, already volume loads of only 70 ppm iron [16], and similar entothelisalisation effects were achieved in nano-doped TPU, aiming to improve the hemocompatibility of medical devices and artificial organs [17]. The general suitability of nano-doped hydrogels as active biomaterial for wound healing was assessed in cytocompatibility, cell proliferation, and migration assays using human dermal fibroblasts and keratinocytes [18]. The hydrogels were processed via electrospinning resulting in a centimeter scale, fully cytocompatible fiber pad for wound coverages [18]. Such gel-based nano-doped biomaterials, processed by 3D printing, are also interesting for the fabrication of RGD-peptide-free scaffolds for tissue engineering, or studies on the differentiation of stem cells in their ion-controlled niche.

References:

[1] Philipp Gabriel, Varatharaja Nallathambi, Jianing Liu, Franziska Staab, Timileyin David Oyedeji, Yangyiwei Yang, Nick Hantke, Esmaeil Adabifiroozjaei, Oscar Recalde-Benitez, Leopoldo Molina-Luna, Ziyuan Rao, Baptiste Gault, Jan T. Sehrt, Franziska Scheibel, Konstantin Skokov, Bai-Xiang Xu, Karsten Durst, Oliver Gutfleisch, Stephan Barcikowski, Anna R. Ziefuss, Boosting Coercivity of 3D Printed Hard Magnets through Nano-Modification of the Powder Feedstock, Advanced Science, 2024, 2407972, https://doi.org/10.1002/advs.202407972

[2] Jianing Liu, Ying Yang, Franziska Staab, Carlos Doñate-Buendia, René Streubel, Bilal Gökce, Fernando Maccari, Philipp Gabriel, Benjamin Zingsem, Detlef Spoddig, Karsten Durst, Michael Farle, Oliver Gutfleisch, Stephan Barcikowski, Konstantin Skokov, Anna R. Ziefuss, Influence of Colloidal Additivation with Surfactant-Free Laser-Generated Metal Nanoparticles on the Microstructure of Suction-Cast Nd–Fe–B Alloy, Advanced Engineering Materials, 25, 22, 2023, 2301054, https://doi.org/10.1002/adem.202301054

[3] I. M. Kusoglu, F. Huber, C. Doñate-Buendía, A. R. Ziefuss, B. Gökce, J. T. Sehrt, A. Kwade, M. Schmidt, S. Barcikowski; Nanoparticle Additivation Effects on Laser Powder Bed Fusion of Metals and Polymers—A Theoretical Concept for an Inter-Laboratory Study Design All Along the Process Chain, Including Research Data Management; Materials 14 (17), 4892; DOI: 10.3390/ma14174892

[4] V. Nallathambi, P. Gabriel, X. Chen, Z. Rao, K. Skokov, O. Gutfleisch, S. Barcikowski, A. R. Ziefuss, B. Gault: Effect of Ag nano-additivation on microstructure formation in Nd-Fe-B magnets built by laser powder bed fusion, Acta Materialia, 2025, https://doi.org/10.1016/j.actamat.2025.121353

[5] Anna R. Ziefuss, Philipp Gabriel, Rene Streubel, Milen Nachev, Bernd Sures, Florian Eibl, Stephan Barcikowski, In-situ composition analysis during laser powder bed fusion of Nd-Fe-based feedstock using machine-integrated optical emission spectroscopy; Materials & Design, 2024, 113211, https://doi.org/10.1016/j.matdes.2024.113211

[6] P. Gabriel, F. Eibl, S. Barcikowski, A. R. Ziefuss, Toward Real-Time Chemical Mapping during Laser Powder Bed Fusion: Robust In-Situ Spectroscopy and 3D Reconstruction, Additive Manufacturing, 105112, 2026, https://doi.org/10.1016/j.addma.2026.105112

[7] Induction of Osteogenic Differentiation of Adipose Derived Stem Cells by Microstructured Nitinol Actuator-Mediated Mechanical Stress.
S. Strauss, S. Dudziak, R. Hagemann, S. Barcikowski, M. Fliess, M. Israelowitz, D. Kracht, J. W. Kuhbier, C. Radtke, K. Reimers, P.M. Vogt PLOS ONE 7, 12 (2012) https://doi.org/10.1371/journal.pone.0051264

[8] M. Willeke, A. Sommereyns, S. Leupold, A. Lüddecke, A. Kwade, N. Hantke, J. T. Sehrt, M. Schmidt, S.Barcikowski, A. R. Ziefuss: Comparative Evaluation of Surface Sensitizers for Near-Infrared Laser Powder Bed Fusion of Polyamide 12, Advanced Engineering Materials, 2025, https://doi.org/10.1002/adem.202500466

[9] N. Stratmann, M. Willeke, S. Leupold, K. Loza, A. Lüddecke, A. Kwade, M. Schmidt, S. Barcikowski, A. R. Ziefuss: Localized Energy Absorption through LaB6 Surface Modification of PA12 Enables Enhanced Tensile Performance in Diode Laser PBF-LB, Chemical Methods, 2025, https://doi.org/10.1002/cmtd.202500101

[10] T. Hupfeld, A. Sommereyns, T. Schuffenhauer, Evgeny Zhuravlev, M. Krebs, S.Gann, O. Keßler, M.Schmidt, B. Gökce, S. Barcikowski, How colloidal surface additivation of polyamide 12 powders with well-dispersed silver nanoparticles influences the crystallization already at low 0.01 vol%, Additive Manufacturing, 36, 2020, https://doi.org/10.1016/j.addma.2020.101419

[11] Plasmon assisted 3D microstructuring of gold nanoparticle-doped polymers.
L. Jonusauskas, M. Lau, P. Gruber, B. Gökce, S. Barcikowski, M. Malinauskas, A. Ovsianikov
Nanotechnology 27, 154001 (2016) https://doi.org/10.1088/0957-4484/27/15/154001

[12] I. M. Kusoglu, S. Garg, A. Abel, P. V. Balachandran, S. Barcikowski, L. Becker, J.-S. Bernsmann, J. Boseila, C. Broeckmann, M. Coskun, M. Dreyer, M. East, M. Easton, N. Ellendt, S. Gann, B. Gökce, M. Goßling, J. Greiner, P. Gruber, M. Grünewald, K. Gurung, N. Hantke, F. Hengsbach, H. Holländer, B. Van Hooreweder, K.-P. Hoyer, Y. Huang, F. Huber, O. Kessler, B. Ö. Kısasöz, S. Kleszczynski, E. Koc, T. Kurzynowski, A. Kwade, S. Leupold, D. Liu, F. Lomo, A. Lüddecke, G. A. Luinstra, D. A. Mauchline, F. Meyer, L. Meyer, P. Middendorf, S. Nolte, M. Olejarczyk, L. Overmeyer, A. Pich, S. Platt, F. Radtke, R. Ramm, S.-K. Rittinghaus, R. Rothfelder, J. Rudlo, M. Schaper, M. L. Scheck, J. H. Schleifenbaum, M. Schmidt, J. T. Sehrt, Y. P. Shabanga, A. Sommereyns, R. Steuer, L. S. Tisha, A. Toenjes, C. Tuck, A. Vaghar, B. Vrancken, Z. Wang, S. Weber, J. Wegner, B.-X. Xu, Y. Yang, D. Zhang, E. Zhuravlev, A. R. Ziefuss: Unveiling the Impact of Nanoparticle-Based Feedstock Modification on Laser Powder Bed Fusion Process: A Wide-Scale Interlaboratory Study along the Entire Process Chain, Advanced Engineering Materials, 2025, https://doi.org/10.1002/adem.202402930

[13] Kuşoğlu, I.M., Ziefuß, A.R., Barcikowski, S., 2024. Booklet for Standard Operational Procedures of DFG SPP2122 Interlaboratory Study measuring the effect of nanoparticles on the entire PBF-LB process chain of AlSi10Mg and PA12. https://doi.org/10.17185/duepublico/82630

[14] Barcikowski, S., Kuşoğlu, I.M., Ziefuß, A.R., Gann, S., Lüddecke, A., Kwade, A., Vaghar, A., Luinstra, G.A., Hantke, N., Sehrt, J.T., Becker, L., Weber, S., Tisha, L.S., Toenjes, A., Ellendt, N., Steuer, R., Zhuravlev, E., Keßler, O., Rothfelder, R., Leupold, S., Sommereyns, A., Huber, F., Schmidt, M., Gurung, K., Vrancken, B., Van Hooreweder, B., Wegner, J., Platt, S., Meyer, L., Kleszczynski, S., Dreyer, M., Hoyer, K.-P., Hengsbach, F., Schaper, M., Coşkun, M.O., Özbay Kısasöz, B., Koç, E., Bernsmann, J.-S., Boseila, J., Schleifenbaum, J.H., Goßling, M., Rittinghaus, S.-K., Gökce, B., Abel, A., Holländer, H., Overmeyer, L., Lomo, F.N., Zhang, D., Easton, M., East, M., Tuck, C., Grünewald, M., Rudloff, J., Gruber, P., Olejarczyk, M., Kurzynowski, T., Shabanga, Y., Mauchline, D., Huang, Y., Wang, Z., Greiner, J., Middendorf, P., Liu, D., Radtke, F., Scheck, M.L., Broeckmann, C., Ramm, R., Nolte, S., Meyer, F., Pich, A.Z., Balachandran, P.V., Gang, S., Yang, Y., Bai-Xiang, X., 2025. DFG SPP2122 Interlaboratory Study Dataset. https://doi.org/10.17185/duepublico/82674

[15] Near-field-enhanced, off-resonant laser sintering of semiconductor particles for additive manufacturing of dispersed Au-ZnO-micro/nano hybrid structures.
M. Lau, R.G. Niemann, M. Bartsch, W. O’Neill, S. Barcikowski
Applied Physics A 114 (2014), Nr. 4, S. 1023-1030 https://link.springer.com/article/10.1007/s00339-014-8270-1

[17] Dose-dependent surface endothelialization and biocompatibility of polyurethane noble metal nanocomposites.
Hess, C. ; Schwenke, A. ; Wagener, P. ; Franzka, S. ; Sajti, C. L. ; Pflaum, M. ; Wiegmann, B. ; Haverich, A. ; Barcikowski, S
Journal of Biomedical Materials Research, Part A 102 (2014), 6, 1909-1920 https://doi.org/10.1002/jbm.a.34860

[18] Water-based, surfactant-free cytocompatible nanoparticle-microgel-composite biomaterials – rational design by laser synthesis, processing into fiber pads and impact on cell proliferation.
N. Million, V. Coger, P. Wilke, C. Rehbock, M. Vogt Peter, A. Pich, S. Barcikowski
BioNanoMaterials, 2017. https://doi.org/10.1515/bnm-2017-0004