Measurement verification of line smoothness and surface roughness of micro products fabricated by two-photon polymerization

Abstract

This paper studies the quality of lines and surfaces fabricated by the two-photon polymerization (TPP) technology. Micro lines and surfaces fabricated by TPP are accumulation of micro spots, and their external shapes can be simulated and predicted from manufacturing parameters, such as laser power, exposure time, scanning speed, spot gap, and line gap. The correctness of predicted shapes is verified by measuring product shapes by SEM and AFM. The purpose of this study is to find the best parameters for increasing line smoothness and reducing surface roughness. Firstly, the total energy absorbed in each point within the work piece space is simulated by adding up all the laser spots of the scanning path. The point with absorbed exposure energy exceeding the resin threshold energy forms a polymerized spot of the product, and the product shape can be obtained. Secondly, micro lines and surfaces with different manufacturing parameters are fabricated and product shapes are measured by both SEM and AFM. The simulated shape and the measured shape of the product with specific manufacturing parameters are compared. Shapes from simulation and fabrication have the same trend. Results of this study can be applied in manufacturing TPP products with complex shapes for better surface quality.