A method of introducing liquid into a gap of a digital microfluidics system for manipulating samples in liquid portions or droplets; the digital microfluidics system comprising a first substrate and a central control unit , wherein said first substrate comprises an array of electrodes , and wherein said central control unit is in operative connection to said electrodes for controlling the selection of individual electrodes thereof and for providing a number of said electrodes with voltage for manipulating liquid portions or droplets by electrowetting; in said digital microfluidics system , a working gap with a gap height is located parallel to the array of electrodes and in-between first and second hydrophobic surfaces ; the two hydrophobic surfaces facing each other at least during operation of the digital microfluidics system , characterized in that the method comprises the steps of: (a) placing a cover on the first substrate of the digital microfluidics system , the cover comprising on one side the second hydrophobic surface and on another side at least one micro-container interface ; said at least one micro-container interface comprising a cone with an inner surface and at least one fluidic access hole formed into the cover and interconnecting the cone and the gap ; (b) providing an essentially uniform height of the gap between said first and second hydrophobic surfaces ; (c) providing at least one micro-container filled with prepackaged liquid reagents; (d) inserting a nozzle of the at least one micro-container into the cone of the micro-container interface of the cover ; (e) creating a sealing form fit contact between the inner surface of the cone of the micro-container interface and an outer surface of the nozzle of the inserted at least one micro-container ; and (f) dispensing liquid by positive displacement from the at least one micro-container into the gap via the at least one fluidic access hole formed in the cover , wherein the injection of liquid into the gap occurs by positive displacement when a piston of the micro-container is pushed down by a mechanical actuation. (a) placing a cover on the first substrate of the digital microfluidics system , the cover comprising on one side the second hydrophobic surface and on another side at least one micro-container interface ; said at least one micro-container interface comprising a cone with an inner surface and at least one fluidic access hole formed into the cover and interconnecting the cone and the gap ; (b) providing an essentially uniform height of the gap between said first and second hydrophobic surfaces ; (c) providing at least one micro-container filled with prepackaged liquid reagents; (d) inserting a nozzle of the at least one micro-container into the cone of the micro-container interface of the cover ; (e) creating a sealing form fit contact between the inner surface of the cone of the micro-container interface and an outer surface of the nozzle of the inserted at least one micro-container ; and (f) dispensing liquid by positive displacement from the at least one micro-container into the gap via the at least one fluidic access hole formed in the cover , wherein the injection of liquid into the gap occurs by positive displacement when a piston of the micro-container is pushed down by a mechanical actuation. <EOS>