Precipitation-induced voltage-dependent ion current fluctuations in conical nanopores

Single conically shaped nanopores produce stable ion current fluctuations when in contact with weakly soluble salts, such as calcium hydrogen phosphate (CaHPO₄) and cobalt hydrogen phosphate (CoHPO₄). The pore spontaneously switches between high and low conductance states, called open and closed states, respectively. Pore opening and closing are linked to the dynamic formation of the calcium and cobalt precipitates at the small opening of the pore. The probabilities of pore opening and closing are voltage-dependent, and this characteristic of ion current signal is known for biological voltage-gated channels. We show that new types of ion current fluctuations are obtained in conditions at which precipitates of CaHPO₄ and CoHPO₄ can form in the pore at the same time.