Infrared-light induced curing of photosensitive resins through photon up-conversion for novel cost-effective luminescent 3D-printing technology

Here we explore the ground-breaking photonic approach for infrared-light induced photo-polymerization of organic resins by using photon up-conversion in rare-earth-doped luminescent materials. In particular, we show outstanding high-intense near-infrared to ultraviolet-blue up-conversion emissions from Tm3+-doped K2YbF5 crystals, energies of which perfectly match the activation energy of light-sensitive resins that contain photo-initiators for radical polymerisation, widely used in medical surgery, odontology or implants applications, as well as in microstereolithography three-dimensional (3D) printing technology. This innovative technique, in which a cost-effective and low-power continuous wave commercial near-infrared laser diode is used, establishes a significant step forward to the state-of-the-art, by offering lower nominal radiation power and exposure time requirements than those of simultaneous two-photon absorption techniques based on powerful femtosecond lasers. We also present quasi-instantaneous laser-writing''-like printing of 3D-structures, which exhibit visible luminescence under infrared light, for novel applications in 3D security-ink stamps or fluorescent labels for visual identification of orthodontic adhesives.