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Advanced ceramics printed with photon-based additive manufacturing deals with anisotropic mechanical properties from the layer-by-layer manufacturing. Motivated by the success in using highly filled transparent slurries containing nanoparticles for powder-based two-photon-polymerization (2PP) for advanced ceramic printing, this works approach is the transfer to Xolography, a volumetric additive manufacturing technology based on linear two-photon excitation and without recoating steps. This paper reports the results of a preliminary investigation optimizing the photocurable slurry to the requirements of Xolography in terms of transparency, over a significantly larger mean free path, compared to 2PP. A feedstock filled with 70 % weight fraction of ceramic particles (∼30 vol%) exhibiting an exceptionally high degree of transparency in the relevant wavelength range of 400–800 nm was prepared from 5 nm zirconia nanoparticles. The high transparency of the photocurable slurry is attributed to the near-monomodal particle size distribution of the zirconia nanoparticles used.

Here we disclose that spiropyrans are able to undergo dynamic covalent exchange via their corresponding merocyanine isomers. In the latter, the indolinium moieties can be exchanged by a Michael-type addition-elimination sequence, in which a methylene indoline attacks a merocyanine and subsequently the initial indoline fragment is cleaved. The rate and position of the exchange equilibrium strongly depend on the reaction conditions as well as the substitution pattern on the methylene indoline fragments. Importantly, spiropyran cross exchange is catalyzed by indolinium salts and provides the opportunity for rapid in situ structural diversification of spiropyrans. This was used as synthetic tool to access various, hitherto inaccessible spiropyrans as potential dual-color photoinitiators for xolography. Moreover, we foresee application to screen dynamic covalent libraries of spiropyrans for photochromic properties and to exploit their light-sensitivity to bias the thermal equilibrium., (© 2025 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Additive manufacturing (AM) of ceramics has significantly contributed to advancements in ceramic fabrication, solving some of the difficulties of conventional ceramic processing and providing additional possibilities for the structure and function of components. However, defects induced by the layer-by-layer approach on which traditional AM techniques are based still constitute a challenge to address. This study presents the volumetric AM of a SiOC ceramic from a preceramic polymer using xolography, a linear volumetric AM process that allows to avoid the staircase effect typical of other vat photopolymerization techniques. Besides optimizing the trade-off between preceramic polymer content and transmittance, a pore generator is introduced to create transient channels for gas release before decomposition of the organic constituents and moieties, resulting in crack-free solid ceramic structures even at low ceramic yield. Formulation optimization alleviated sinking of printed parts during printing and prevented shape distortion. Complex solid and porous ceramic structures with a smooth surface and sharp features are fabricated under the optimized parameters. This work provides a new method for the AM of ceramics at µm/mm scale with high surface quality and large geometry variety in an efficient way, opening the possibility for applications in fields such as micromechanical systems and microelectronic components., (© 2024 Wiley‐VCH GmbH.)

Additive manufacturing techniques continue to improve in resolution, geometrical freedom, and production rates, expanding their application range in research and industry. Most established techniques, however, are based on layer-by-layer polymerization processes, leading to an inherent trade-off between resolution and printing speed. Volumetric 3D printing enables the polymerization of freely defined volumes allowing the fabrication of complex geometries at drastically increased production rates and high resolutions, marking the next chapter in light-based additive manufacturing. This work advances the volumetric 3D printing technique xolography to a continuous process. Dual-color photopolymerization is performed in a continuously flowing resin, inside a tailored flow cell. Supported by simulations, the flow profile in the printing area is flattened, and resin velocities at the flow cell walls are increased to minimize unwanted polymerization via laser sheet-induced curing. Various objects are printed continuously and true to shape with smooth surfaces. Parallel object printing paves the way for up-scaling the continuous production, currently reaching production rates up to 1.75 mm 3  s -1 for the presented flow cell. Xolography in flow provides a new opportunity for scaling up volumetric 3D printing with the potential to resolve the trade-off between high production rates and high resolution in light-based additive manufacturing., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)