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).
