Nanopore formation method

A nanopore formation method for forming a nanopore in a membrane, the method comprising:

• introducing an aqueous solution at a first pH into a first solution tank and a second solution tank insulated by the membrane;
• securing hydrophilicity of a surface of the membrane;
• replacing the aqueous solution at the first pH in the first solution tank and the second solution tank with an aqueous solution at a second pH lower than the first pH after the hydrophilicity of the surface of the membrane is secured;
• and
• immersing an electrode in each of the first solution tank and the second solution tank containing the aqueous solution at the second pH to cause dielectric breakdown and form the nanopore in the membrane,
• wherein securing the hydrophilicity of the surface of the membrane is determined when a second capacitance noise is higher than a first capacitance noise by twice or more, and
• wherein forming the nanopore in the membrane includes:
• applying a pulse voltage to the electrodes;
• measuring a current flowing when a voltage lower than the pulse voltage is applied to the electrodes;
• and
• determining that the dielectric breakdown is caused when the current is larger than a threshold current.

A nanopore formation method for forming a nanopore in a membrane, the method comprising:

• introducing an aqueous solution at a first pH into a first solution tank and a second solution tank insulated by the membrane;
• preparing an electric device that applies a voltage between electrodes or causes a current to flow between the electrodes;
• applying a direct-current voltage of less than 10 V between the electrodes using the electric device in a state without a load to measure a first square root noise;
• applying the direct-current voltage of less than 10 V between the electrodes using the electric device in a state with a load to measure a second square root noise;
• replacing the aqueous solution at the first pH in the first solution tank and the second solution tank with an aqueous solution at a second pH lower than the first pH after hydrophilicity of a surface of the membrane is secured;
• and
• immersing an electrode in each of the first solution tank and the second solution tank containing the aqueous solution at the second pH to cause dielectric breakdown and form the nanopore in the membrane.