Modern three-dimensional nanofabrication requires both additive and subtractive processes. However, both processes are largely isolated and generally regarded as incompatible with each other. In this study, we developed simultaneous additive and subtractive fabrication processes using two-photon polymerization followed by femtosecond (fs) laser multiphoton ablation. To demonstrate the new capability, submicrometer polymer fibers containing periodic holes of 500-nm diameter and microfluidic channels of 1-µm diameter were successfully fabricated. This method combining both two-photon polymerization and fs laser ablation improves the nanofabrication efficiency and enables the fabrication of complex three-dimensional micro-/nanostructures, promising for a wide range of applications in integrated optics, microfluidics and microelectromechanical systems.

In this study, the degree of conversion (DC) of an acrylic-based resin (IP-L 780) in two-photon polymerization (TPP) is systematically investigated via Raman microspectroscopy. A quantitative relationship between TPP laser parameters and the DC of the resin is established. Nonlinear increase in DC with increased laser average power is observed. The resin DC is more sensitive to the laser average power than the laser writing speed. Nanoindentation was employed to correlate the results obtained from Raman microspectroscopy with the mechanical properties of microstructures fabricated by TPP. At constant writing speeds, microstructures fabricated with high laser average powers possess high hardness and high reduced Young’s modulus (RYM), indicating high DCs. The results are in line with high DCs measured under the same TPP parameters in Raman microspectroscopy. Raman microspectroscopy is proved to be an effective, rapid, and nondestructive method characterizing microstructures fabrication by TPP.