| Abstract [eng] |
Investigation of Femtosecond Pulse Induced Polymerization Properties of Photosensitive Nano-composites High cytotoxicity of virtually all commercially available photoinitiators prevents 3D microstructures fabricated by direct laser writing (DLW) from wide application in emerging biomedical applications as manufacturing of drugdelivery agents or bio-degradable implants. Thus the research of new materials as bio-compatible polymerization enhancers is of high importance. Also, there is no agreement between research groups regarding temperature kinetics while polymerization reaction takes place as experimental attempts to evaluate local temperature changes concludes to completely contrary results so far. In this work we investigate the influence of gold nanoparticles (Au NP) (as potentially bio-compatible polymerization enhancer) to photosensitivity of PEG-DA-700 photopolymer. We found PEG-DA-700 monomers / water solution to be a suitable prepolymer for hydrogels fabrication even when monomers concentration was reduced to as low as 50 wt%. The research shows that doping PEG-DA-700 monomer with Au NP (doping concentrations varying between 3·10−3 and 4.8·10−3 wt%), enhances photopolymer sensitivity as measured polymerization threshold values were 25-35% lower compared to pure PEG-DA monomers mixture. In this work we also test bovine serum albumin stabilized gold (BSA-Au) nanoclusters in PEG-DA and NaYbF4:Er3+ upconverting nanoparticles (UCNPs) in SZ2080 as thermosensitive agents for in-situ local temperature change detection due to polymerization reaction in DLW process. Luminescence imaging experiments show that BSA-Au fluorescence intensity is being quenched as exposing pulse energy increases. However, due to low quantum yield of nanoclusters, temperature dependent spectral shifts were not clearly observed and calibration of local temperature changes was not implemented. In high contrast to this, luminescence of Er3+ -doped UCNPs exhibited obvious changes of thermally-coupled spectral bands intensity ratios while prepolymer being processed in different DLW regimes. We calculated average fitted temperature changes around polymerized voxel to be ∆T1 < 3 K when writing within process window and goes up to ∆T2 < 170 K in overexposing regime. The obtained results suggests Au doped nanocomposite to be a perspective material for 3DLL applications as it consists of completely bio-compatible components. Our suggested T-sensitive nano-composites might be found interesting for further investigation towards contactless thermo-sensing applications in nanoscale. |
