Fluidic unit for discrete element trapping

A fluidic unit for trapping a discrete element in a liquid sample having a volume less than 1 microliter and comprising a fluidic circuit comprising:

• a well for receiving a volume of a liquid comprising the discrete element;
• a well output conduit;
• a metering chamber in fluid communication with the well through said well output conduit, for metering a liquid sample of the volume of the liquid received from the well;
• and
• an obstructable waste output conduit for evacuating an excess portion of the volume of the liquid from the metering chamber,
• wherein the fluidic unit extends along an axis X2 and in the direction of increasing X2 from a lower surface to an upper surface of the fluidic unit;
• wherein the well opens on the upper surface of the fluidic unit through the upper opening of the well;
• and
• wherein the waste output conduit is openable on the lower surface of the fluidic unit through the lower opening of the waste output conduit.