Fig. 6: Fabricating the miniaturized bionic ocean-battery using conductive hydrogel matrix.

a The diagram of a miniaturized bionic ocean-battery fabricated in a single-chamber electrochemical device. The bottom is PPy conductive hydrogel encapsulating the strains E3, S3 and G. The upper layer is cyanobacteria culture of strain Syn7942-FL130. The four-species community forms a complete carbon cycle (CO₂-sucrose-lactate-acetate-CO₂). In this unidirectional electron flow, the energy is inputted in the form of light and outputted in the form of electricity. The SEM image shows the porous structure of PPy conductive hydrogel. The air cathode is shown on the left. b Electricity generation of the miniaturized bionic ocean-battery powered by light directly. The systems running in the dark, the systems free of cyanobacteria, and the systems free of E. coli were included as negative controls. The light source is white light-emitting diodes with intensity of 20 W·m⁻². Data are presented as mean values ± SD from n = 3 independent experiments. c Polarization curve and power curve of the miniaturized bionic ocean-battery. d The overall energy balance of the miniaturized bionic ocean-battery. The energy flux and energy efficiency of light-to-sucrose, sucrose-to-lactate, lactate-to-electricity and light-to-electricity are presented. The current/power densities were normalized to the geometrical area of receiving the light. Source data are provided as a Source Data file.