Passau researchers develop 4D-CT methods for 4D printing materials in the EU network X-CELERATEY

The University of Passau is participating in the Marie Skłodowska-Curie doctoral network X-CELERATE, which is developing new methods for 4D X-ray computed tomography (4D-CT). The focus is on additive manufacturing processes using “smart” materials that change in a targeted way under external stimuli. While conventional 3D printing produces rigid components, 4D printing creates structures whose shape, color, or mechanical properties adapt to temperature, magnetic fields, or light. Suitable measurement and evaluation chains that capture the dynamics of such systems during stimulation are still lacking for design rules and material models.

Prof. Dr. Christoph Heinzl, holder of the Chair of Cognitive Sensor Systems at the University of Passau and head of the research group at the Fraunhofer Development Center for X-ray Technology (EZRT) on knowledge-based image processing, explains: “Laboratory-based, time-resolved X-ray imaging is ideally suited for investigating smart materials. It captures dynamics of these materials that were previously invisible.”

Together with Prof. Tomas Sauer, Chair of Mathematics with a focus on Digital Image Processing, tailored 4D-CT strategies, new reconstruction and analysis methods, as well as visualization pipelines are to be developed. A key component is phase-contrast imaging, which makes small density differences in polymer foams, hydrogels, or composite layers visible and is therefore relevant for 4D printing materials such as stimuli-responsive polymers.

The transnational consortium comprises 14 partners from nine countries and is coordinated by the University of Antwerp. X-CELERATE starts on 1 December 2025, runs for four years, and is part of Horizon Europe. According to the University of Passau, two doctoral positions will be created—one at Sauer’s chair and one in Heinzl’s EZRT group.

“In X-CELERATE we focus on bringing forth the next generation of research engineers with an entrepreneurial mindset. The fact that the University of Passau is now involved in such projects shows how valuable and right the establishment of the Fraunhofer group and the cooperative professorship in Passau was,” explains Prof. Dr. Sauer.

For 3D-printing practice, the combined methodology promises robust data foundations: it can derive material parameters for simulations, accelerate design iterations, and objectify quality inspections of 4D components—from prototypes to small-batch production.