Sample preparing arrangement and a method relating to such an arrangement

A chip which uses magnetically controlled beads to regulate localization at discrete elements of the chip agents present in a fluid medium, the chip comprising:

• a substrate comprising a plurality of elements, each comprising an integrated magnetic field generating device;
• a plurality of beads;
• and
• a controller controllably coupled to each device;
• wherein each device independently, controllably and reversibly generates alternative attractive and repulsive magnetic fields through influence of a control signal generated by the controller, said magnetic fields sufficient to independently, controllably and reversibly magnetically attract and repel one of the beads to and from the element, respectively, to regulate localization of a subset of the agents at the element.