Method and apparatus for orienting sperm in a fluid stream

A flow cytometry apparatus nozzle to sort sperm cells in a fluid stream by chromosome content comprising:

• a. a nozzle body having a fluid stream entry portion and a fluid stream exit portion and an interior surface separating both portions and along which a fluid stream is adapted to flow;
• b. the interior surface of the nozzle including a first, a second and a third axially tapered region for progressively accelerating the speed of a fluid stream in a downstream direction toward the exit portion, at least two of the regions having generally elliptical cross sectional shapes oriented in different directions for applying torsional forces to a fluid stream passing there through, tending to bring sperm cells in the stream into a desired orientation.

A method of orienting animal sperm cells in a flow cytometry apparatus, the method comprising the steps of:

• introducing a fluid containing sperm cells into a fluid stream;
• directing the fluid stream containing the sperm cells under a pressure in the range of 20 to 40 psi through a nozzle having one or more tapered regions for accelerating the speed of the fluid stream in a downstream direction toward a nozzle orifice having a diameter in the range of 50-70 microns, one or more of the tapered regions having a generally elliptical cross sectional shape for applying a torsional force to the fluid stream tending to bring the cells into a desired orientation as they pass through the orifice at a rate in the range of 30,000 to 50,000 sperm cells per second.