Digital microfluidics system manipulates samples in liquid droplets within disposable cartridges that have bottom layer, top layer, and gap between the bottom and top layers. The system has a base unit with cartridge accommodation sites and a central control unit for controlling selection of individual electrodes of electrode arrays and for providing these electrodes with individual voltage pulses for manipulating liquid droplets within the cartridges by electrowetting. The system further has board accommodation sites located at the cartridge accommodation sites that each can take up a swappable electrode board having an electrode array and electrical board contact elements individually connected to electrodes of the electrode array. Each board accommodation site has electrical base unit contact elements that are connected to the central control unit and that are configured to engage with the electrical board contact elements of a swappable electrode board that is placed at the board accommodation site.