This invention relates generally to devices, systems, and methods for avoiding bubble formation in a fluidic chamber during filling of the fluidic chamber with a liquid. A first and second piece are operatively coupled to form the fluidic chamber. A protrusion protrudes into a volume of the fluidic chamber such that there is a distance of minimal approach between an apex of the protrusion and a surface of the fluidic chamber. The protrusion forms a channel that extends from one of an inlet and the outlet of the fluidic chamber to the protrusion apex. A maximum distance of travel through the fluidic chamber volume exists between the inlet and the outlet. A cross-sectional area of the fluidic chamber volume increases from the protrusion apex to a transverse plane of the fluidic chamber and decreases from the transverse plane to the other one of the inlet and the outlet.