Systems and methods for active particle separation

A method for extracting particles contained in a ferrofluid medium, the method comprising:

• suspending particles of different sizes in a ferrofluid medium;
• containing the ferrofluid medium in a reservoir having at least one wall, an extraction opening, and a central portion, the central portion being configured near or around a central axis and away from the at least one wall;
• applying a first magnetic field to at least a portion of the reservoir, the first magnetic field being generated by a first magnetic field source located proximate to the extraction opening;
• wherein the first magnetic field is configured to:
• exert a force on at least a group of the particles of a predetermined size, and
• direct the group of particles of the predetermined size in a first direction towards a central portion of the reservoir and away from the extraction opening such that the group of the particles is suspended in the central portion of the reservoir.