High-aspect 3D two-photon polymerization structuring with widened objective working range (WOW-2PP)

We developed a novel two-photon polymerization (2PP) configuration for fabrication of high-aspect three-dimensional (3D) structures, with an overall height larger than working distance of the microscope objective used for laser beam focusing into a photosensitive material. This method is based on a modified optical 2PP setup, where a microscope objective (1003 high N.A.), immersion oil and cover glass can be moved together into the photosensitive material, resulting in an effective higher and wider objective working range (WOW-2PP). The proposed technique enables the fabrication of high-aspect structures with sub-micrometer process resolution. 3D structures with a height of 7 mm are demonstrated, which could hardly be built with the conventional 2PP set-up due to refractive index mismatch and laser beam disturbances.