Abstract: A method of determining the charge of at least one test particle, comprising: applying one of an electric current or a voltage across an aperture connecting two chambers, whereby the chambers are at least partially filled with electrolyte and whereby the at least one test particle is suspended in the electrolyte of at least one of the chambers; measuring the other of the electric current or voltage across the aperture; varying a pressure differential between the two chambers; and determining the charge based on the measurements of the electric current or voltage.

Abstract: The flow of particles (18) in an aperture (10) between two reservoirs (14) and (15) is controlled by suspending the particles (18) in a fluid (17) within the aperture (10), applying a potential difference across the aperture (10) so as to tend to electrophoretically transport the particles (18) between a region of higher potential field and a region of lower potential in the fluid (17), applying a pressure differential across the aperture (10) so as to tend to transfer the fluid (17) with the particles (18) therein though the aperture (10) from a high-pressure reservoir (14) to a low-pressure reservoir (15), and adjusting the potential difference and/or the pressure differential across the aperture (10) in order to achieve precise control over the translation of the particles (18) within the aperture (10).

Abstract: A method of determining the charge of at least one test particle, comprising: applying one of an electric current or a voltage across an aperture connecting two chambers, whereby the chambers are at least partially filled with electrolyte and whereby the at least one test particle is suspended in the electrolyte of at least one of the chambers; measuring the other of the electric current or voltage across the aperture; varying a pressure differential between the two chambers; and determining the charge based on the measurements of the electric current or voltage.

Abstract: The flow of particles (18) in an aperture (10) between two reservoirs (14) and (15) is controlled by suspending the particles (18) in a fluid (17) within the aperture (10), applying a potential difference across the aperture (10) so as to tend to electrophoretically transport the particles (18) between a region of higher potential field and a region of lower potential in the fluid (17), applying a pressure differential across the aperture (10) so as to tend to transfer the fluid (17) with the particles (18) therein though the aperture (10) from a high-pressure reservoir (14) to a low-pressure reservoir (15), and adjusting the potential difference and/or the pressure differential across the aperture (10) in order to achieve precise control over the translation of the particles (18) within the aperture (10).