Additive Manufacturing of 3D‐Architected Multifunctional Metal Oxides

• Published in: Advanced materials (Weinheim) Vol. 31; no. 33; pp. e1901345 - n/a
• Main Authors: Yee, Daryl W., Lifson, Max L., Edwards, Bryce W., Greer, Julia R.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.08.2019
• Subjects: 3D printing; Additive manufacturing; Coordination compounds; electromechanics; Electron microscopes; Grain size; Materials science; Metal oxides; Photopolymers; Slurries; Smart materials; Synthesis; two‐photon lithography; Voltage drop; Zinc oxide; Zinc oxides; metal oxides; two-photon lithography; 3D printing; electromechanics; zinc oxide
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.201901345

Additive manufacturing (AM) of complex three‐dimensional (3D) metal oxides at the micro‐ and nanoscales has attracted considerable attention in recent years. State‐of‐the‐art techniques that use slurry‐based or organic–inorganic photoresins are often hampered by challenges in resin preparation and synthesis, and/or by the limited resolution of patterned features. A facile process for fabricating 3D‐architected metal oxides via the use of an aqueous metal‐ion‐containing photoresin is presented. The efficacy of this process, which is termed photopolymer complex synthesis, is demonstrated by creating nanoarchitected zinc oxide (ZnO) architectures with feature sizes of 250 nm, by first patterning a zinc‐ion‐containing aqueous photoresin using two‐photon lithography and subsequently calcining them at 500 ºC. Transmission electron microscopy (TEM) analysis reveals their microstructure to be nanocrystalline ZnO with grain sizes of 5.1 ± 1.6 nm. In situ compression experiments conducted in a scanning electron microscope show an emergent electromechanical response: a 200 nm mechanical compression of an architected ZnO structure results in a voltage drop of 0.52 mV. This photopolymer complex synthesis provides a pathway to easily create arbitrarily shaped 3D metal oxides that could enable previously impossible devices and smart materials. Fabrication of 3D nanoarchitected multifunctional metal oxides is performed through a facile method using a metal‐ion‐containing aqueous photoresin, which is polymerized using two‐photon lithography and calcined to give the metal oxide structure. Zinc oxide microstructures, with sub‐micrometer features, fabricated using this technique exhibit an electromechanical response that could enable the production of previously impossible 3D smart devices.