Zhiheng Zhang, Nathaniel Corrigan and Cyrille Boyer from the Boyer Laboratory at UNSW Sydney, in collaboration with the University of Auckland, have reported a significant breakthrough by combining a “living” polymerisation process with 3D printing (Zhang Z., Corrigan N., Bagheri A., Jin J., Boyer C., Angew. Chem. Int. Ed. 2019. https://doi.org/10.1002/anie.201912608). The photomediated “living” 3D printing process (based on the PET-RAFT polymerisation technique developed by the Boyer group) uses metal-free and non-toxic components in water and was activated using harmless green light irradiation. The inclusion of RAFT agent, which imparts the “living” character to the polymer material, was also used to adjust the mechanical properties of the material and allowed the stiffness and elasticity of the 3D printed material to be tuned. The 3D printed polymer materials were then able to be easily modified after fabrication by performing successive polymerisation from the “living” polymer chains, which produced 3D printed objects with complex and tailorable chemical and physical properties.

Additionally, by controlling the light irradiation 4D printed materials (3D printed materials that respond to an external stimulus) were formed, as demonstrated by 3D printed objects that reversibly folded when exposed to water. As such, this photocontrolled RAFT 3D and 4D printing system will facilitate the development of functional and stimuli-responsive 3D printed materials. Furthermore, as the reaction components are non-toxic and can be polymerized under harmless visible light, these systems should be used in the future for varied applications, including nanomedicine and other bioapplications.