Hydrodynamic focusing device

A hydrodynamic focusing device, comprising:

• a first flow channel;
• a second flow channel dimensioned with a smaller cross-section than a cross-section of the first flow channel;
• a wall that at least partially defines an envelopment region that is connected in-line between the first flow channel and the second flow channel, the first flow channel, the second flow channel, and the envelopment region collectively defining a flow direction extending through the first flow channel, through the envelopment region, and through the second flow channel;
• and
• a chimney including a chimney body and a sample fluid inlet, the chimney body extending from the wall that at least partially defines the envelopment region into the envelopment region, the chimney body having smaller lateral and vertical dimensions than lateral and vertical dimensions of the envelopment region, the sample fluid inlet terminating at a first end within the envelopment region that is coincident with an end of the chimney body and faces at least partially perpendicular to the flow direction, such that the sample fluid inlet is configured to supply a sample fluid into the envelopment region in a direction that is at least partially perpendicular to the flow direction,
• wherein the chimney body and the sample fluid inlet are concentric and together form the chimney and each have an elongate profile, the elongate profile having
• a rounded leading edge facing the first flow channel,
• an opposing trailing edge, and
• long edges connecting the rounded leading edge and the opposing trailing edge, the long edges being tapered towards the opposing trailing edge.