Photopolymerization assisted by up-conversion nanoparticles for three-dimensional low-power photonics applications

Photopolymerization assisted by up conversion nanoparticles (UCNPs) are reported to have promising potential in the biological field due to the unique fluorescent features of UCNPs. Here, we demonstrate a novel method in the fabrication of three-dimensional (3D) features at low power level with unique photo-luminescence property through the incorporation of UCNPs under a far-field direct laser writing (DLW) configuration. Equipped with long lifetime of excited energy levels, UCNPs were employed to function as the excitation light source for inducing controlled reversible deactivation radical polymerization through activating polymerization photo reagents via resonance energy transfer in the localized area surrounding the UCNPs, hence generating polymerized micro-scale features upon an incident near-infrared laser beam. UCNPs with unique emission qualities were custom-synthesized and dispersed in a monomer-based mixture containing polymerization photo-reagents to formulate a photo-sensitive nanocomposite. A thin film sample based off the nanocomposite was then placed under a DLW scheme for the fabrication of 3D micro-structures at low power level (100sW/cm2 for the writing laser beam intensity). Able to fabricate 3D micro-structures at very low power level with unique photo-luminescent properties compared to the traditional two-photon polymerization technique, this new method of laser fabrication method assisted by UCNPs has significant potential applications in research domains such as 3D low-power nanoscale optical memory, high-resolution imaging/display, functional micro-photonics devices and 3D micro-prototyping.