fig2

Figure 2. (A) SEM image; (B) corresponding elemental mapping; and (C) EDS spectrum of a typical area on the ACO electrode surface; (D) Images of liquid Ga printed on different substrates, including PE, paper, and PET; (E) Related ACO electrodes printed on PE, paper, and PET substrates; (F) Images of a typical printed two-electrode system with ACO as the working electrode, carbon black as the counter electrode, and PE as the substrate; (G) Schematic representation of the flexible ACO electrode; (H) Photographs of flexible ACO electrodes bent to various angles. ACO: Annealed Cu-Oxide; EDS: energy-dispersive X-ray spectroscopy; PE: polyethylene; PET: PE terephthalate; SEM: scanning electron microscopy.