Three-dimensional micro/nano-fabrication by integration of additive and subtractive femtosecond-laser direct writing processes

Advanced three-dimensional (3D) micro/nano-fabrication requires both additive and subtractive fabrication processes. However, method possessing both additive and subtractive fabrication capabilities was rarely reported. In this study, we developed a complementary 3D micro/nano-fabrication process by integrating the additive two-photon polymerization (TPP) and the subtractive multi-photon ablation (MPA) into a single platform of femtosecond-laser direct writing process. Functional device structures including polymer fiber Bragg grating containing periodic holes of 500-nm diameter and 3D microfluidic systems containing arrays of channels of 1-μm diameter were successfully fabricated and characterized. The combination of TPP and MPA processes enhances the nanofabrication efficiency and enables the fabrication of complex 3D micro/nano-structures that are impractical to produce by either TPP or MPA alone. The new fabrication method is promising for a wide range of applications including integrated optics, micro-fluidics, and microelectromechanical systems.