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.