A method comprises the steps of: providing a digital microfluidics system (1) with electrodes (2) attached to a substrate (3) and covered by a hydrophobic surface (5), and a control unit (7) for manipulating liquid droplets (8-1) by electrowetting; providing in close proximity to electrodes (2) a magnetic conduit (9) for directing a magnetic field of a backing magnet to the first hydrophobic surface (5); providing on the hydrophobic surface (5) a liquid droplet (8-1) that comprises magnetically responsive beads (11); moving by electrowetting the liquid droplet (8-1) with the magnetically responsive beads (11) until at least a part of which is placed atop of the magnetic conduit (9); actuating the backing magnet (10) of the magnetic conduit (9) and attracting/concentrating magnetically responsive beads (11); and while actuating the backing magnet (10), moving by electrowetting the liquid droplet (8-1)' with decreased number of magnetically responsive beads (11) away from the specific magnetic conduit (9). Also disclosed are a method for suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics and a disposable cartridge (17) to carry out the methods therein.
