Periodic Reporting for period 1 - EagleEye (A novel 3D printEr for lArGe-area light-based additive manufacturing with uLtra-high rEsolution combining digital light procEssing and two-photon polYmErization)
Période du rapport: 2022-12-01 au 2024-11-30
The EagleEye project aims to develop an advanced 3D printing optical setup to optimize two-photon polymerization (2PP) for large-area processing. In 2PP, tightly focused laser radiation initiates polymerization in photosensitive materials at specific points within the material's volume. This process creates a voxel (volumetric pixel) in regions where the laser intensity exceeds a defined threshold. The nonlinear nature of 2PP allows the voxel to remain confined within the focal volume, with its dimensions determined by the laser intensity. By combining precise laser focusing with accurate beam guidance, 2PP enables the direct fabrication of intricate 3D structures from computer-generated models, achieving feature sizes in the submicron range.
Compared to other manufacturing techniques with similar resolution, 2PP offers exceptional design freedom, making it suitable for advanced applications in healthcare, optics, and photonics. However, its inefficiency for large-area processing remains a significant challenge. The precision of 2PP, akin to drawing with a fine pencil, allows for intricate details but makes large-scale structures time-consuming to produce.
The EagleEye project addresses this challenge by integrating 2PP with digital light processing (DLP), a lower resolution but efficient printing approach, into a single optical setup. This integration enables a layer-by-layer printing process where DLP creates bulk structures or areas with less detail, while 2PP is reserved for fine-resolution features. Instead of accelerating 2PP, the EagleEye approach applies it selectively where high precision is essential, maintaining its resolution capabilities.
Potential applications for the EagleEye setup include Lab-on-Chip systems, such as microfluidic structures, and scaffolds designed to foster superior cell growth and tissue regeneration.
Compared to other manufacturing techniques with similar resolution, 2PP offers exceptional design freedom, making it suitable for advanced applications in healthcare, optics, and photonics. However, its inefficiency for large-area processing remains a significant challenge. The precision of 2PP, akin to drawing with a fine pencil, allows for intricate details but makes large-scale structures time-consuming to produce.
The EagleEye project addresses this challenge by integrating 2PP with digital light processing (DLP), a lower resolution but efficient printing approach, into a single optical setup. This integration enables a layer-by-layer printing process where DLP creates bulk structures or areas with less detail, while 2PP is reserved for fine-resolution features. Instead of accelerating 2PP, the EagleEye approach applies it selectively where high precision is essential, maintaining its resolution capabilities.
Potential applications for the EagleEye setup include Lab-on-Chip systems, such as microfluidic structures, and scaffolds designed to foster superior cell growth and tissue regeneration.
The primary technical challenge of the EagleEye project was the integration of DLP and 2PP technologies into a single setup, enabling automated layer-by-layer printing using both approaches. This challenge arose from the fundamental differences between these technologies, such as their operation at different wavelengths of light and their distinct procedural requirements in conventional implementations. Moreover, the system needed to account for emerging advancements in 2PP, including parallelized and projection-based printing techniques, as well as the adoption of novel laser sources.
To address these requirements, the EagleEye system was designed to enable the independent and alternating use of DLP and 2PP (see images attached). This design ensured compatibility with diverse 2PP configurations and advancements, making the system highly adaptable for future developments in advanced 3D printing. In this way, by focusing on long-term sustainability and adaptability, the EagleEye system is well-positioned to remain relevant and useful beyond the project's duration.
In the EagleEye system, DLP printing utilized a commercially available DLP projector with a 405 nm LED and a digital micromirror device (DMD). The DMD produced patterns over a 4 cm × 6.5 cm area with an average pixel resolution of approximately 50 µm, providing sufficient resolution to complement the high precision achievable with 2PP printing.
For 2PP, a tightly focused 780 nm laser beam was directed through photosensitive materials using a galvanometric scanner. The optical setup included a motorized nosepiece capable of holding up to three microscope objectives, enabling seamless switching between objectives. This feature allowed for 2PP printing at varying levels of precision, increasing the system's versatility for printing features across multiple length scales.
The printing process was realized in a bottom-up approach, supported by dedicated software developed specifically for objective lens switching and DLP printing. In particular, the DLP printing software includes automated stage movements and the slicing of arbitrary computer models to generate individual patterns from 3D structures as layers for printing. For the 2PP process, the software was externally optimized to align with the specific requirements of the EagleEye setup.
In parallel with the hardware and software advancements, photosensitive materials compatible with both DLP and 2PP methods were investigated. Commercially available DLP resins were modified with a photoinitiator to enable effective polymerization for 2PP without compromising DLP performance.
As a proof of concept, the EagleEye system successfully fabricated a microfluidic chip featuring a functionalized micro-filter as well as other structures for demonstration (see attached image).
To address these requirements, the EagleEye system was designed to enable the independent and alternating use of DLP and 2PP (see images attached). This design ensured compatibility with diverse 2PP configurations and advancements, making the system highly adaptable for future developments in advanced 3D printing. In this way, by focusing on long-term sustainability and adaptability, the EagleEye system is well-positioned to remain relevant and useful beyond the project's duration.
In the EagleEye system, DLP printing utilized a commercially available DLP projector with a 405 nm LED and a digital micromirror device (DMD). The DMD produced patterns over a 4 cm × 6.5 cm area with an average pixel resolution of approximately 50 µm, providing sufficient resolution to complement the high precision achievable with 2PP printing.
For 2PP, a tightly focused 780 nm laser beam was directed through photosensitive materials using a galvanometric scanner. The optical setup included a motorized nosepiece capable of holding up to three microscope objectives, enabling seamless switching between objectives. This feature allowed for 2PP printing at varying levels of precision, increasing the system's versatility for printing features across multiple length scales.
The printing process was realized in a bottom-up approach, supported by dedicated software developed specifically for objective lens switching and DLP printing. In particular, the DLP printing software includes automated stage movements and the slicing of arbitrary computer models to generate individual patterns from 3D structures as layers for printing. For the 2PP process, the software was externally optimized to align with the specific requirements of the EagleEye setup.
In parallel with the hardware and software advancements, photosensitive materials compatible with both DLP and 2PP methods were investigated. Commercially available DLP resins were modified with a photoinitiator to enable effective polymerization for 2PP without compromising DLP performance.
As a proof of concept, the EagleEye system successfully fabricated a microfluidic chip featuring a functionalized micro-filter as well as other structures for demonstration (see attached image).
The EagleEye project has progressed beyond the mere combination of two established printing techniques with the following achievements.
In 2PP, achieving the highest precision traditionally requires oil-immersion objective lenses with high numerical apertures (NAs). These lenses allow for the tightest laser focusing but present challenges when integrated into optical setups like the one developed in the EagleEye project. The primary difficulties result from the limited working distances of oil-immersion lenses and the high costs associated with refractive index-matching materials in large volumes. Such constraints further emphasize the importance for further research into photosensitive materials to fully exploit the potential of integrating DLP and 2PP printing. As a step in this direction, the project investigated various photoinitiators to enhance the efficiency of 2PP printing.
To tackle the precision limitations of 2PP from another perspective, the EagleEye project explored 2PP's ability to modulate voxel size through rapid laser intensity adjustments. By implementing precise laser power regulation during the printing process, voxel dimensions were tailored to meet the precision requirements of specific regions within a 3D structure. This method was successfully demonstrated, achieving high-fidelity structuring with dry objective lenses featuring NAs below 1 —comparable to the results typically achieved with oil-immersion lenses. This capability was particularly effective in fabricating advanced micro-optics for imaging applications, with potential applications envisioned in Lab-on-Chip systems.
In 2PP, achieving the highest precision traditionally requires oil-immersion objective lenses with high numerical apertures (NAs). These lenses allow for the tightest laser focusing but present challenges when integrated into optical setups like the one developed in the EagleEye project. The primary difficulties result from the limited working distances of oil-immersion lenses and the high costs associated with refractive index-matching materials in large volumes. Such constraints further emphasize the importance for further research into photosensitive materials to fully exploit the potential of integrating DLP and 2PP printing. As a step in this direction, the project investigated various photoinitiators to enhance the efficiency of 2PP printing.
To tackle the precision limitations of 2PP from another perspective, the EagleEye project explored 2PP's ability to modulate voxel size through rapid laser intensity adjustments. By implementing precise laser power regulation during the printing process, voxel dimensions were tailored to meet the precision requirements of specific regions within a 3D structure. This method was successfully demonstrated, achieving high-fidelity structuring with dry objective lenses featuring NAs below 1 —comparable to the results typically achieved with oil-immersion lenses. This capability was particularly effective in fabricating advanced micro-optics for imaging applications, with potential applications envisioned in Lab-on-Chip systems.