A disposable cartridge used in a digital microfluidics system has a bottom layer with first hydrophobic surface, a rigid cover plate with second hydrophobic surface, and a gap there-between. The bottom layer is a flexible film on an uppermost surface of a cartridge accommodation site of a system, attracted to and spread over the uppermost surface by an underpressure. A lower surface of the plate and the flexible bottom layer are sealed to each other. The assembled cartridge is removed from the cartridge accommodation site in one piece and potentially includes samples and processing fluids. The system has a base unit and a cartridge accommodation site with an electrode array of individual electrodes and a central control unit for controlling selection of individual electrodes and for providing these electrodes with individual voltage pulses for manipulating liquid droplets within the gap by electrowetting.