Figure 1. Scheme of the energy conversion and storage process using a single conical pore.

(a) Steady-state current (I) - potential (V_N) curves showing electrical rectification (pH = 7) and ohmic response (pH = 3, control experiment). (b) A randomly fluctuating electric potential V_R(t) is externally applied using a voltage source. (c) The output electric current I(t) for pH = 7 gives a non-zero time average current <I>. (d) This net current <I> allows the charging of an external load capacitor connected in series to the nanopore. As the capacitor is charged, a potential difference (voltage) V_C(t) which drives a reverse current opposing the charging process is set up.