Two-Photon Polymerization Printing with High Metal Nanoparticle Loading

Abstract

Two-photon polymerization (2PP) is an efficient technique to achieve high-resolution, three-dimensional (3D)-printed complex structures. However, it is restricted to photocurable monomer combinations, thus presenting constraints when aiming at attaining functionally active resist formulations and structures. In this context, metal nanoparticle (NP) integration as an additive can enable functionality and pave the way to more dedicated applications. Challenges lay on the maximum NP concentrations that can be incorporated into photocurable resist formulations due to the lasertriggered interactions, which primarily originate from laser scattering and absorption, as well as the limited dispersibility threshold. In this study, we propose an approach to address these two constraints by integrating metallic Rh NPs formed ex situ, purposely designed for this scope. The absence of surface plasmon resonance (SPR) within the visible and near-infrared spectra, coupled with the limited absorption value measured at the laser operating wavelength (780 nm), significantly limits the laser-induced interactions. Moreover, the dispersibility threshold is increased by engineering the NP surface to be compatible with the photocurable resin, permitting us to achieve concentrations of up to 2 wt %, which, to our knowledge, is significantly higher than the previously reported limit (or threshold) for embedded metal NPs. Another distinctive advantage of employing Rh NPs is their role as promising contrast agents for X-ray fluorescence (XRF) bioimaging. We demonstrated the presence of Rh NPs within the whole 2PP-printed structure and emphasized the potential use of NP-loaded 3D-printed nanostructures for medical devices.

Two-photon polymerization lithography for imaging optics

“…Furthermore, the fabrication of desired materials for intricate 3D structures using TPL holds immense promise for enhancing imaging performance and creating complex optical systems [226][227][228][229]. For instance, the integration of metals or metal alloy mounts can facilitate the incorporation of optical elements [230], leading to improved imaging contrast and enabling mirror reflections. These functionalities have been challenging to achieve with polymers, except through total internal reflection.…”

Laboratory Liquid-Jet X-ray Microscopy and X-ray Fluorescence Imaging for Biomedical Applications

“…Contrast-mediated XFI was enabled by using elements whose electron absorption edge matches the X-ray source energy [38,42,51]. The energy-resolved signal acquisition permits the simultaneous detection and localization of several elements, such as Mo, Ru, and Rh, through their K α XRF emission [26].…”

Iterative nanoparticle bioengineering enabled by x-ray fluorescence imaging

“…X-ray fluorescence (XRF) has recently been used for in vivo imaging of small animals with high elemental specificity, by designing inorganic NPs as contrast agents, composed of elements whose absorption edge matches the x-ray source energy (24 keV), such as molybdenum (Mo), ruthenium (Ru), or rhodium (Rh) ( 16 – 20 ). In our previous study, the formation of a core-shell hybrid nanostructure, with an XRF active core (MoO 2 NPs) and a passivating dye-doped silica (SiO 2 ) shell, enabled dual optical and XRF imaging and reduced the cytotoxicity in vitro, as compared to uncoated MoO 2 NPs ( 18 ).…”