Major-axis planning method for fabrication of high aspect ratio structure based on two-photon photopolymerization technology

The smallest forming unit in two-photon photopolymerization (TPP) micro-manufacturing technology is the voxel, the appearance of which resembles a spheroid. Traditional TPP micro-manufacturing is planned using the minor-axis dimension of a spheroid, which is smaller than its major-axis, thus, the spatial resolution can achieve submicron level. TPP can be used to manufacture microstructures with complex shapes. However, such fine spatial resolution inevitably lowers the overall manufacturing speed. For a microstructure with a height of hundred micrometers, the prolonged manufacturing time substantially increases the risk of manufacturing failure. Whereas typical methods use the minor-axis dimension for manufacturing planning, this study developed a novel major-axis planning (MAP) method that uses the longest dimension of the voxel. In this study, the MAP was realized in a 4-axis micro-manufacturing system (i.e., a rotation axis was added to the 3-axis motion stage). Specifically, a specially designed L-type glass substrate was first placed on the rotation axis and was rotated 90°, rendering the working plane parallel to laser beams. Subsequently, horizontal laser scanning was performed, during which the laser focus moved from the working plane horizontally, to polymerize a high-aspect-ratio structure. The commercial polymer OrmoComp was used with the MAP; only 10 s was required to fabricate a microstructure that had a height of 100 μm and an aspect ratio of 17. This study verified that TPP micro-manufacturing on a voxel’s major axis can fabricate microstructures. Moreover, the L-type glass substrate can be controlled programmably to rotate an L-type glass substrate for 4-axis TPP micro-manufacturing in the future.