Recently, photo-controlled reversible addition-fragmentation chain transfer (RAFT) polymerization has been successfully applied in digital light processing 3D printing. It provides a convenient way to tune the surface properties of the 3D printed object. However, so far, 3D micro-and nanostructures and reconfigurations based on photo-induced RAFT polymerization have not been presented. In this work, one macro-photoiniferter, synthesized by photocontrolled RAFT polymerization is applied, to 3D direct laser writing. Thanks to the exquisite spatial control of the photoreaction, 3D microstructures with feature sizes of around 500 nm are successfully obtained. Taking advantage of the presence of dormant polymeric RAFT agents, photo-induced postmodification of the printed microstructures is highlighted via the elaboration of multi-chemistry patterns including thermo-responsive ones. These results open new perspectives in multi-material and 4D micro-printing.

Photoactivated Reversible Deactivation Radical Polymerization (RDRP) technologies have emerged very recently in the field of 3D printing systems especially at the macroscale in vat‐photopolymerization‐based processes such as digital light processing (DLP). Contrary to conventional free radical photopolymerization, photoRDRP in 3D printing leads to 3D objects with living character and thus confers them the unique ability to be post‐modified after fabrication. While 3D direct laser writing (3D DLW) by two photon polymerization has become a standard for fabrication of complex 3D micro‐objects, the use of RDRP and its associated benefits has so far been under‐investigated at that scale. Herein, a photoresist suitable for 3D DLW based on nitroxide mediated photopolymerization (NMP2) is developed. The photopolymerization efficiency for fabrication of micro‐structures and their subsequent post‐modification are investigated regarding the laser power and the wavelength of excitation. Moreover, highly tunable, precise, and successive surface patterning of 2D and 3D multi‐material microstructures are demonstrated thanks to the spatial and temporal control offered by the photo‐induced post‐modification. This work highlights new directions to be explored in order to accelerate the adoption of RDRP in 3D printing based on photopolymerization.