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Femtosecond Laser Multiphoton Polymerization (FLMP) is a rapid prototyping technique enabling fabrication of 3D microstructures of complex geometry with 100 nm spatial resolution and unmatched flexibility. FLMP is based on nonlinear light and matter interaction - a tightly focused pulsed light beam, having high intensities (~TW/cm2), modifies the photosensitive material within femtoliter volume. After the exposure sample is immersed in the developer bath, the unexposed regions of the material are removed and a free standing 3D micro/nanostructure is revealed on the substrate. Such point-by-point photostructuring enables to directly write functional micro/nanostructures which can be applicable in photonics, microoptics, micromechanics, microfluidics and being transferred to the production of artificial polymeric scaffolds, metamaterials and plasmonic functional devices. In this thesis, experimental results on FLMP 3D micro/nanostructuring of various photopolymers are presented. It starts from the construction and development of the laser fabrication setup. Issues like optimization of the laser structuring parameters for increasing fabrication resolution and production throughput are presented and discussed. Functional micro/nanodevices manufactured out of acrylate, hybrid organic-inorganic and biodegradable photopolymers are demonstrated and their performance is investigated. During the work several problems were solved: 1) Development of novel laboratory setup based on diode pumped solid state femtosecond Yb:KGW amplified laser system combined with high translation speed and precision linear motion stages designed for rapid FLMP micro/nanostructuring over a large area. Various irradiation wavelengths and pulse repetition rates were tested in order to optimize the nonlinear excitation of the photosensitive material. High sample translation speed (increasing from µm/s to mm/s) corresponding to rapid structure writing were applied in order to manufacture micro/nanostructured samples over a large areas (from tens of µm to tens of mm). 2) Study on improvement of 3D structuring spatial resolution choosing the appropriate photosensitive materials and optimizing the exposure was investigated. Hybrid materials containing metal isopropoxides were found to be best for complex-shaped rigid structure fabrication at micro/nanoscale with 200 nm reproducible resolution and acrylate based materials were applied to initiate self-polymerization which can reach < 100 nm spatial resolution. It was shown, that precise 3D structuring can be performed in not photosensitized materials (containing no photoinitiator) initiating the photopolymerization reaction via avalanche ionization. 3) FLMP fabrication of microoptical elements, integrated and bi-functional components was realized. Their characterization of optical properties was performed. Materials, having refractive index matching the one of the glass and being ultralow shrinking during the processing, were found to be suitable for manufacturing of custom shaped microoptical elements and bi-functional components ensuring surface roughness to be sufficient (< /20 for visible ranges) for optical quality requirements. Obtained results showed, it can be applied in molding of flight flow at micro scale, for coupling as well as guiding or sensing light. 4) Study on photostructuring of biocompatible materials in 3D with < 1 µm resolution required for biomedical applications was performed. Optimization of fabrication over a large area was done in order to manufacture microstructured samples suitable for tissue engineering applications. In vitro and in vivo experiments with stem cells and laboratory animals were done to assess the material and scaffold biocompatibility. In brief, in this thesis the FLMP technique is overviewed and technological details are described, original results are presented as well as future prospects are discussed. |
