Surface Modification of 3D-Printed Micro- and Macro-Structures via In Situ Nitroxide-Mediated Radical Photopolymerization

Photo-controlled reversible-deactivation radical polymerization (RDRP) has recently emerged in light-based 3D printing at macro- and micro-scales, enabling the elaboration of objects with (re-)configurable surface properties. The authors' previous work exploits nitroxide-mediated radical photopolymerization (NMP2) in 3D micro-printing and subsequent surface modification, by employing analkoxyamine-based photoresist via 3D direct laser writing (DLW). However, this photoresist suffers from its low photosensitivity to wavelengths above 760 nm, limiting its suitability for commercial 3D DLW setups. To tackle these issues, a new strategy-in situ NMP2 based on a photoresist containing acommercial photoinitiator and a photosensitive-nitroneis proposed. This photoresist is well-suited for wavelengths commonly used by 3D DLW systems to obtain well-defined 3D microstructures. Importantly, the in-situ formation of alkoxyamine during fabrication allows photo-induced surface modification of microstructures, highlighted by precise and successive surface patterning. Thesurface modification can be conducted at 800 nm or at wavelengths up to 860 nm. Subsequently, the impact of light wavelength and intensity isinvestigated to understand surface modification. The simple preparation of this novel photoresist allows facile adaptation to digital light processing for 3D macro-printing. This work broadens the scope of photo-controlled RDRP in 3D printing and greatly facilitates "living" 3D micro- and macro-printing. A new strategy is developed in 3D printing. Based on a photoresist containing a nitrone and a commercial photoinitiator, it can be facilely adapted to 3D direct laser writing and digital light processing, and facilitates precise post-surface modification attributing to the in-situ formation of alkoxyamines during printing. This strategy bridges micro- and macro-3D printing, fuelling the development of "living" printing.image