A digital microfluidics system with electrodes attached to a substrate and covered by a hydrophobic surface, and a control unit for manipulating liquid droplets by electrowetting; providing in close proximity to electrodes a magnetic conduit for directing a magnetic field of a backing magnet to the first hydrophobic surface; providing on the hydrophobic surface a liquid droplet that has magnetically responsive beads; moving by electrowetting the liquid droplet with the magnetically responsive beads until a part of which is placed atop of the magnetic conduit; actuating the backing magnet of the magnetic conduit and attracting/concentrating magnetically responsive beads; and while actuating the backing magnet, moving by electrowetting the liquid droplet with decreased number of magnetically responsive beads away from the specific magnetic conduit. Also disclosed are a method for suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics and a disposable cartridge to carry out the methods.