A method for concentrating electrically charged objects in a non-Newtonian liquid medium comprises: feeding a sample containing electrically charged objects into a channel having a flow axis, a first transverse cross-section orthogonal to the flow axis, and at least one second transverse cross-section orthogonal to the flow axis, one dimension of the second cross-section being less than the corresponding dimension of the first cross-section; and applying a hydrodynamic flow in a direction of the channel together with the application, in the opposite direction, of an electric field in the channel, thus making it possible to move the electrically charged objects in the channel along the flow axis from the first cross-section to the second cross-section, stop the objects, and concentrate the objects in at least one area upstream from the second transverse cross-section.

A method for concentrating electrically charged objects in a non-Newtonian liquid medium comprises: feeding a sample containing electrically charged objects into a channel having a flow axis, a first transverse cross-section orthogonal to the flow axis, and at least one second transverse cross-section orthogonal to the flow axis, one dimension of the second cross-section being less than the corresponding dimension of the first cross-section; and applying a hydrodynamic flow in a direction of the channel together with the application, in the opposite direction, of an electric field in the channel, thus making it possible to move the electrically charged objects in the channel along the flow axis from the first cross-section to the second cross-section, stop the objects, and concentrate the objects in at least one area upstream from the second transverse cross-section.

A field flow fractionation apparatus includes a separation channel provided with an inlet port and an outlet port at both ends and forming a space through which a carrier fluid flows between the inlet port and the outlet port, a separation membrane which is a wall surface that defines the separation channel and is parallel to a channel flow in which a carrier fluid flows in the separation channel from the inlet port toward the outlet port, and has a property of permeating the carrier fluid and not permeating particles to be separated, and a discharge port that discharges the carrier fluid having permeated through the separation membrane to outside. At least a part of the surface of the separation membrane is an ion exchangeable region in which a functional group having ion exchangeability is modified.

The invention relates to a system (700) for treating molecules or particles of interest carried by a viscoelastic liquid, which comprises: a means (715) for establishing a laminar flow, during at least one portion, referred to as concentration phase, of the operating time of the system, of the viscoelastic liquid in a concentration, stacking and/or purification device (705), said device comprising a concentration area having, in the direction of said flow, an intake cross-section surface that is larger than the cross-section surface of each outlet channel, and a means (725) for applying an electric field between the intake and the outlet of the concentration area during the concentration phase, the action of the electric field on the molecules or particles of interest being, in the concentration area, opposite to the direction of said flow and causing the molecules or particles of interest to be retained at least in the concentration area;
which also comprises a modulation means (730) configured to control the means for applying the electric field in order to apply, after the concentration phase, an electric field with intensity other than zero and lower than the intensity of the electric field applied during the concentration phase.

A field flow fractionation apparatus includes a separation channel provided with an inlet port and an outlet port at both ends and forming a space through which a carrier fluid flows between the inlet port and the outlet port, a separation membrane which is a wall surface that defines the separation channel and is parallel to a channel flow in which a carrier fluid flows in the separation channel from the inlet port toward the outlet port, and has a property of permeating the carrier fluid and not permeating particles to be separated, and a discharge port that discharges the carrier fluid having permeated through the separation membrane to outside. At least a part of the surface of the separation membrane is an ion exchangeable region in which a functional group having ion exchangeability is modified.

The invention relates to a system (700) for treating molecules or particles of interest carried by a viscoelastic liquid, which comprises: a means (715) for establishing a laminar flow, during at least one portion, referred to as concentration phase, of the operating time of the system, of the viscoelastic liquid in a concentration, stacking and/or purification device (705), said device comprising a concentration area having, in the direction of said flow, an intake cross-section surface that is larger than the cross-section surface of each outlet channel, and a means (725) for applying an electric field between the intake and the outlet of the concentration area during the concentration phase, the action of the electric field on the molecules or particles of interest being, in the concentration area, opposite to the direction of said flow and causing the molecules or particles of interest to be retained at least in the concentration area;
which also comprises a modulation means (730) configured to control the means for applying the electric field in order to apply, after the concentration phase, an electric field with intensity other than zero and lower than the intensity of the electric field applied during the concentration phase.