Photopolymerization induced by up-conversion nanoparticles for three-dimensional low-power nanoscale writing

Photopolymerization induced by up conversion nanoparticles (UCNPs) are reported to have promising potential in the biological and nano-imaging field. Here, a novel method of nanoscale writing at low power level is demonstrated through the incorporation of UCNPs under a two-beam 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 two-beam super-resolution writing scheme for the fabrication of 3D micro-structures at low power level (100sW/cm2 for the writing laser beam intensity). Able to generate 3D nanoscale-features at low power level with unique photo-luminescent properties in comparison with the traditional two-photon writing, this new nanoscale writing technique possesses significant application potential in fields of nanophotonics such as 3D micro-prototyping, 3D low-power nanoscale optical data storage, nanoscale-resolution imaging and functional nanoscale-photonic devices.