NOVELTY - The fluid transfer device (100) has an outlet branch that is configured to split a fluid from the inlet branch channels into a respective several outlet branch channels. A fluid outlet interface is fluidically coupled with the outlet branch channels, and transfers the fluid in the outlet branch channels into a right fluid channel (104). An inlet branch, the output branches, the inlet branch channels and the outlet branch channels are arranged such that the fluid exits from the fluid outlet interface, is distributed in a two-dimensional manner across a large cross-sectional area.    USE - Fluid transfer device for transferring fluid e.g. liquid and/or gas, solid particles and fluid sample, between two fluid channels with different diameter, used in fuel cell of sample separation device such as micro-fluid measuring device, life-science device, liquid chromatography device, high performance liquid chromatography (HPLC) device, gas chromatography device, electrophoresis device and/or gel electrophoresis device, for separating fractions of fluid.    ADVANTAGE - The fluid transfer device can enable the transfer of a fluid between fluid channels of differing diameter with a small dead volume and without undesired effects on a detection of the fluid. Since the multi-stage branching logic is impressed on the fluid over the whole splitting-up process in each case in a well-defined manner, the fanning-out of the fluid can be controlled in a targeted manner. Hence the problems with jet streams, turbulence or dead volumes can be suppressed or completely eliminated. The fluid transfer device can ensure artifact-free and low-dead-volume decoupling of the fluid into the flow cell. This can increase the separation capacity of the respective sample separation device. The splitting-up of a fluid fraction at a hierarchical stage of connected branch channels is mounted in each case and downstream can take place, such that the fluid quantity can be split into equal sub-volumes or flow rates. This can suppress the formation of artifacts in branch channels or at the outlet interface.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) flow cell for detecting fluid feedable from left fluid channel;    (2) sample separation device for separating fractions of fluid; and    (3) method for transferring fluid from left fluid channel into second fluid channel.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram showing the HPLC system.    Separation device (30)    Fluid transfer device (100)    Left fluid channel (102)    Right fluid channel (104)    Fluid outlet opening (150)