[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Increasing Two-Photon Polymerization Fabrication Speed of 3D Structures for Cell Interaction Studies

摘要： Expanding cell studies and tissue engineering from a 2D platform to a 3D mimic of their natural environment demands fabrication methods capable of creating scaffolds covering large volumes with feature sizes down to a few μm. Two-photon polymerization (TPP) is a direct writing method capable of fabricating free-form 3D structures with sub-wavelength features and is therefore well-suited for template fabrication for cell motility and tissue engineering. We demonstrate 9 times increased fabrication speed for 3D periodic structures using a diffractive optical element (DOE) that creates 9 beamlets from one femtosecond laser beam. The parallelized method maintains fabrication quality and each beamlet is used for the fabrication of the base structures that form the periodic pattern. Two 3D designs were fabricated from bio-compatible SZ2080 polymer, where the distance between structures are accurately matching the distance between beamlets. Both of the fabricated structure arrays consists of 3x3 patterns with 9 individual structures in each pattern and covers an area of 450x450 μm. The first design contains unsupported interconnections between individual structures and field-of-views (FOV’s). The second design contains additional supporting structures that stabilize those interconnections between individual structures and FOV’s. For the first design high similarity is observed between the individual base structures inside each FOV, while at the stitching positions between different FOV’s discrepancies are observed leading to gaps in the overall periodic pattern. The gaps arise from contraction of the polymer material during the development process and subsequently drying process. It is related to large leapfrog movement of the stage system (>150 μm) between FOV’s. In the second design, additional support was added between individual one voxel thin structures to overcome this problem. Using this strategy, no gaps are observed and any remaining mismatch is less than 100 nm for stitching of structures. Additional studies were performed where HeLa-cells were incubated for 24 hours on both scaffolds and cell affinity is studied. We observe in both cases that HeLa-cells attach to wall and corner segments of the periodic designs and furthermore HeLa-cells are seen stretching the full length of the individual wall segments. In summary, we show that parallelization of the fabrication process has the potential to make TPP a fast method for large volume periodic 3D structure.