Fig. 2: Conductance state changing kinetics in FON.
A I-V curves of a PimB-modified micropipette in symmetric 0.1 M KCl containing K3Fe(CN)6 with different concentration, scan rate 50 mV·s−1. B Optical microscopy image of air-droplet interface movement in a capillary connected with a PimB-modified micropipette in 0.1 M KCl (left) and 0.1 M KCl+1 mM K3Fe(CN)6 (right) under −3 V bias. C Typical I-V curve of a PimB-modified micropipette in asymmetric solution (inner, 0.1 M KCl+1 mM K3Fe(CN)6; outer, 0.1 M KCl), scan rate 50 mV·s−1. Inset, schematic illustration of the K+ governed RC process (right) and the Cl− governed NDR process (left). D Schematic illustration of the ion conductance changing mechanism of FON, (i) initial low conductance state with few Pim-\({{{{\rm{Fe}}}}({{{\rm{CN}}}})}_{6}^{3-}\) interaction in the PimB layer; (ii) Pim-\({{{{\rm{Fe}}}}({{{\rm{CN}}}})}_{6}^{3-}\) adsorption contributed to raising ion conductance under negative bias; (iii) High conductance state with the majority of PimB layer adsorbed by \({{{{\rm{Fe}}}}({{{\rm{CN}}}})}_{6}^{3-}\), inverted EOF pumped external KCl solution into FON; (iv) Desorption of \({{{{\rm{Fe}}}}({{{\rm{CN}}}})}_{6}^{3-}\) in KCl solution contributed to the recovered conductance and EOF in FON.
