Laser 3D nanostructuring of polymers: mechanisms study and targeted applications

Direct Laser Writing (DLW) is a technique nowadays employed for the efficient fabrication of trully three-dimensional (3D) micro/nano-structures. It has been shown that the optimization of exposure conditions and material properties can lead to sub-100 nm fabrication spatial resolution in all three dimensions. However, a better understanding of the mechanisms of localized photo-modification and threshold behaviour of the material under intense light exposure has not been achieved yet. The control of light-matter interaction is of great importance in order to optimize manufacturing quality as well as reproducibility. In this report we present an overview of DLW based on threshold polymerization supported by systematic study of localized polymerization at the nanoscale. Results proving that two-photon absorption is not al- ways playing the main role are demonstrated, by showing that threshold material response to tightly focused light can be initiated not only with femtosecond, but also with picosecond, nanosecond pulsed or even CW laser irradiation. These results suggest that the combination of lower cost picosecond lasers operating at high pulse repetition rate are suitable for the practical implementation of 3D nanopolymerization in photonics, microoptics, microfluidics and biomedicine, since there is efficient utilization of the delivered photo- energy. Alternatively, femtosecond lasers induce the most efficient polymerization in terms of required photo-energy and variety of processable materials for the fabrication of 3D structures.We also demonstrate how integrated microoptical elements and functional biomedical devices can be fabricated. Their optical performance and biological interactions are also characterized. The potential to manufacture 3D high-fidelity structures on various substrates, such as optical fibers, metallic and nano-rough surfaces is demonstrated