Fig. 1. Fabrication process and principle of three-dimensional micro-nano structure of metal oxide. (a) Fabrication process; (b) compositions of photoresist material; (c) transmittance of photoresist under different wavelengths; (d) coordination reaction between metal ion and polymer scaffold; (e) demonstration of three-dimensional micro-nano structures of metal oxides

Fig. 2. Factors influencing loading rates of photoresist metal ions. (a) Ion loading rates of photoresist at different R; (b) loading rates of different metal ions

Fig. 3. Characterization of coordination reaction. (a) Raman spectra of photoresist before and after coordination; (b) XPS spectrum of O 1s orbital of microscopic scaffold before coordination; (c) XPS spectrum of O 1s orbital of microscopic scaffold after coordination

Fig. 4. Polymeric scaffolds printed under different laser processing parameters

Fig. 5. Three-dimensional micro-nano structures of metal oxides fabricated under different coordination reaction conditions

Fig. 6. EDS element distributions and energy spectra of three-dimensional micro-nano structures of metal oxides

Fig. 7. XRD patterns of three-dimensional micro-nano structures of metal oxides. (a) NiO sample; (b) CoO sample; (c) Ni_0.5Co_0.5O sample

Fig. 8. Stress-strain curve of CoO octahedral lattice metamaterial structure