In this paper, we present a new approach for ion-enrichment and ion-depletion effect (IEID) in micro-nanofluidic chips without external power source. The method utilizes different reducibility of various electrodes in the weak oxidizing solution to generate the electrochemical potential and then induce IEID at a micro-nano junction. The results show that the average gray values of the micro-nano junction based on Al-Pt, Fe-Pt, and Cu-Pt electrodes increase from 14.7 to 40.2, 27.1, 15.0 after 20 s, and electric currents for Al-Pt, Fe-Pt, and Cu-Pt electrodes are 5.0, 2.9 and 0 nA respectively. Metal cations generating from oxidation-reduction reaction and electro-osmotic convection flow are evaluated and their influences to IEID can be neglected in this case. The IEID method based on the electrochemical potential is power-free and weak flow convective that will be beneficial to the integrity of micro-nanofluidic chips and stability of IEID.
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