Continuous charge separation of electrified air–water two-phase bulk flow

•A two-phase flow electricity charge separator (TPECS) is proposed that enables charge separation and selective charge collection.•The working principle of TPECS is elucidated based on flow visualization and electrical signals.•The average power of TPECS with various types (single, multi, and stacked multi) is analyzed.•The stacked multi TPECS lights up 93LEDs validating practicality. This study introduces the concept of generating electricity by selectively separating and moving charges in water. If positive and negative charges in a fluid can be separated and discharged to create a potential difference, it is a unique approach to generate electricity and has the advantage of providing direct current output. We proposed a new design that maximizes the potential difference by first discharging the free charge in the diffusive layer inside the water through an external electrode, and then electrically separating and discharging the fixed charge near the channel surface by selectively using solid surfaces with different surface potentials. As a proof of concept, we fabricated a channel-type charge separator and verified its working mechanism through quantitative experimental data analysis. Examination of the electrical signals validated the symmetry of signals from individual electrodes, affirming selective collection of separated charges in a fluid. We verified the performance and practicality of the two-phase flow electricity charge separator (TPECS) under different flow conditions. It was also possible to stack the channels, and an electrical power of up to 2.99 μW was produced from a structure of 12 stacked channels. Capacitor charging was executed employing the 12 stacked channels. The charging rate of the 2.2nF capacitor reached 9.46 V/s, facilitating the illumination of 93 red LEDs.