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Lignin, one of the most abundant biomaterials and a large‐scale industrial waste product, is a promising filler for polymers as it reduces the amount of fossil resources and is readily available. 3D printing is well‐known for producing detailed polymer structures in small sizes at low waste production. Especially light‐assisted 3D printing is a powerful technique for production of high‐resolution structures. However, lignin acts as a very efficient absorber for UV and visible light limiting the printability of lignin composites, reducing its potential as a high‐volume filler. In this work, the decolorization of lignin is presented for high‐resolution 3D printing of biocomposites with lignin content up to 40 wt.%. Organosolv lignin (OSL) is decolorized by an optimized low‐energy process of acetylation and subsequent UV irradiation reducing the UV absorbance by 71%. By integration of decolorized lignin into bio‐based tetrahydrofurfuryl acrylate (THFA), a lignin content of 40 wt.% and a resolution of 250 µm is achieved. Due to the reinforcing properties of lignin, the stiffness and strength of the material is increased by factors of 15 and 2.3, respectively. This work paves the way for the re‐use of a large amount of lignin waste for 3D printing of tough materials at high resolution. [ABSTRACT FROM AUTHOR]

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]