High-resolution 3D photopolymerization assisted by upconversion nanoparticles for rapid prototyping applications

Abstract

Three-dimensional (3D) rapid prototyping technology based on near-infrared light-induced polymerization of photocurable compositions containing upconversion nanomaterials has been explored. For this aim, the rationally-designed core/shell upconversion nanoparticles NaYF4:Yb3+,Tm3+/NaYF4, with the distinct ultraviolet-emitting lines and unprecedentedly high near-infrared to ultraviolet conversion efficiency of have been used. The upconverted ultraviolet photons were capable to efficiently activate photoinitiators contained in light-sensitive resins under moderate intensities of NIR excitation below 10 W cm−2 and induce generation of radicals and photopolymerization in situ. Near infrared-activated polymerization process, both at the millimeter and sub-micron scales, was investigated. Polymeric macro- and microstructures were fabricated by means of near infrared laser scanning photolithography in the volume of liquid photocurable compositions with focused laser light at 975 nm wavelength. Examination of the polymerization process in the vicinity of the nanoparticles shows strong differences in the rate of polymer shell growth on flat and edge nanoparticle sides. This phenomenon mainly defines the resolution of the demonstrated near infrared - ultraviolet 3D printing technology at the micrometer scale level.

Light‐Responsive Inorganic Biomaterials for Biomedical Applications

“…Recently, a high-resolution 3D photopolymerization was developed in which UCNPs, dispersed in a liquid mixture of photocurable composition, emitted UV light to activate the photoinitiators under moderate intensities of NIR excitation below 10 W cm −2 for free-radical polymerization ( Figure 9D). [146] This research found that the heterogenous distribution of photoluminescence intensity around UCNP would cause different morphologies of polymer growth from the surface of a single UCNP due to the different polymer growth kinetics. Moreover, it required a minimum concentration of UC-NPs to grow geometrically connected polymeric objects for 3D printing.…”

“…Adapted under the terms of the Creative Commons Attribution 4.0 International License. [146] Copyright 2018, Springer Nature.…”

“…The UV light conversion efficiency of UCNPs is around 2% at an NIR intensity of 25 W cm −2 , which is still far from the safe range of laser intensity usage in biomedical applications, especially at 980 nm. [146] The biocompatibility and photophysical complexity of UCNPs have not been fully investigated. Overall, the unique up-conversion ability of UCNPs will ensure the growth of its research efforts in the field of light-responsive biomaterials.…”

Near‐Infrared Light Driven Photopolymerization Based On Photon Upconversion

“…This polymerization allows fabrication of 3D polymeric structures inside photocurable compositions, which was similar to two‐photon polymerization. This UCNP‐assisted photopolymerization could also be potentially utilized for control of formation of 3D shapes with a non‐contact manner inside tissues …”

Polymers for Regenerative Medicine Structures Made via Multiphoton 3D Lithography

“…and comparable photoactivation to standard Pi [112], gold nanoparticles are promising in biological applications as a replacement for standard PIs. Finally, enhanced and/or controlled photosensitivity can be realized with other nanoadditives such as ZrO 2 [161] or upconverting lanthanide-doped upconversion materials [162]. Thus, this approach can be considered to be extremely versatile and applicable to multiple materials.…”