Fluorescent flow analysis of in situ material exchange in two-photon 3D printing

Recent advancements in two-photon polymerization (2PP) allowed for the precise and versatile fabrication of three-dimensional nano- and microscale structures, making it ideal for use in microelectronics, optoelectronics, photonics, and biomedical engineering. This research demonstrates the effective fabrication of multimaterial microstructures by an in situ material exchange technique using a commercial printhead system. Therefore, the effect of pre-existing microstructures on the laminar exchange flow was investigated, revealing areas of zero-flow and residual material. Residual material can be minimized with extended times of flow. In addition, the study shows a novel application idea for lateral multimaterial microlens printing. On large surfaces, we achieved very good lateral lens alignment as well as in situ material exchange. Lateral multimaterial printing provides substantial benefits over typical vertical lenses in optics and photonics integration. The technique included printing a core lenslet and peripheral lenslets utilizing custom materials for the in situ exchange. Overall, our results demonstrate the adaptability of multimaterial printing via in situ material exchange inside a commercial 2PP system, which broadens design options and improves functioning across multiple technological domains.