3D Nanoprinting of Heterogeneous Metal Oxides with High Shape Fidelity.

3D nanoprinting can significantly enhance the performance of sensors, batteries, optoelectronic/microelectronic devices, etc. However, current 3D nanoprinting methods for metal oxides are suffering from three key issues including limited material applicability, serious shape distortion, and the difficulty of heterogeneous integration. This paper discovers a mechanism in which imidazole and acrylic acid synergistically coordinate with metal ions in water. Using the mechanism, this work develops a series of metal ion synergistic coordination water-soluble (MISCWS) resins for 3D nanoprinting of various metal oxides, including MnO 2 , Cr 2 O 3 , Co 3 O 4 , and ZnO, as well as heterogeneous structures of MnO 2 /NiO, Cr 2 O 3 /Al 2 O 3 , and ZnO/MgO. Besides, the synergistic coordination effect results in a 2.54-fold increase in inorganic mass fraction within the polymer, compared with previous works, which effectively mitigates the shape distortion of metal oxide microstructures. Based on this method, this work also demonstrates a 3D ZnO microsensor with a high sensitivity (1.113 million at 200 ppm NO 2 ), surpassing the conventional 2D ZnO sensors by tenfold. The method yields high-fidelity 3D structures of heterogeneous metal oxides with nanoscale resolution, paving the way for applications such as sensing, micro-optics, energy storage, and microsystems.