Droplet formation systems for flow cytometers
A droplet forming flow cytometer system ( 1 ) allows high speed processing without the need for high oscillator drive powers through the inclusion of an oscillator or piezoelectric crystal ( 10 ) within the nozzle volume ( 3 ) and directly coupled to the sheath fluid. The nozzle container ( 27 ) continuously converges so as to amplify unidirectional oscillations ( 11 ) which are transmitted as pressure waves through the nozzle volume ( 3 ) to the nozzle exit so as to form droplets from the fluid jet. A variation in substance concentration is achieved through a movable substance introduction port ( 9 ) which is positioned within a convergence zone ( 32 ) to vary the relative concentration of substance to sheath fluid while still maintaining optimal laminar flow conditions. This variation may be automatically controlled through a sensor and controller configuration.
1. A method of creating a droplet from a jet of a flow cytometer comprising:
introducing a flow of sheath fluid into a nozzle, said sheath fluid having a primary flow direction through the nozzle;
converging said sheath fluid in a convergence zone in the nozzle;
introducing a flow of a substance at a location within said sheath fluid in said convergence zone;
adjusting the location along the primary flow direction at which said substance is introduced within said convergence zone;
allowing said sheath fluid to exit from said nozzle; and
forming at least one droplet from said sheath fluid after allowing said sheath fluid to exit from said nozzle.
2. A method of creating a droplet from a jet of a flow cytometer according to claim 1 wherein said adjusting the location at which said substance is introduced within said convergence zone comprises establishing a desired concentration of said substance relative to said sheath fluid.
3. A method of creating a droplet from a jet of a flow cytometer according to claim 1 or 2 wherein said adjusting the location at which said substance is introduced within said convergence zone comprises establishing laminar flow of said substance within said sheath fluid.
4. A method of creating a droplet from a jet of a flow cytometer according to claim 1 wherein said adjusting the location at which said substance is introduced within said convergence zone is automatic.
5. A method of creating a droplet from a jet of a flow cytometer according to claim 1 wherein said adjusting the location at which said substance is introduced within said convergence zone comprises:
sensing values representative of conditions within said flow cytometer; and
automatically moving said location based upon said sensed values.
6. A method of creating a droplet from a jet of a flow cytometer according to claim 5 wherein said conditions are at least one of the following: the pressure of said sheath fluid; the pressure of said substance; the location at which said droplet is formed; the rate at which droplet is determined to contain some of said substance; or a property of said substance.
7. A method of creating a droplet from a jet of a flow cytometer according to claim 1 wherein said substance is introduced through a substance tube and wherein said adjusting the location at which said substance is introduced within said convergence zone comprises replacing said substance tube.