Method of generating a fluid stream in a microfluidic device

1. A method of flow cytometry, comprising the steps of:

a. providing a variable volume container having a flexible wall;

b. establishing an amount of fluid in said variable volume container;

c. exerting an amount of pressure in the range of about 70 psi to 200 psi with an amount of a gas on an exterior surface of said flexible wall of said variable volume container;

d. providing a conduit between said variable volume container and a flow path of a flow cytometer;

e. generating a fluid stream of said amount of fluid in said flow path of said flow cytometer by exerting said amount of pressure with an amount of gas on said exterior surface of said flexible wall of said variable volume container having a fluid stream pressure of between 25 psi and about 50 psi;

f. intermittently entraining a particle in said fluid stream in said flow path of said flow cytometer;

g. generating oscillations in said fluid stream to establish a plurality of droplets;

h. establishing said particle in one of said plurality of droplets;

i. illuminating said particle in said one of said plurality of droplets for a duration of time;

j. detecting an emission generated by said particle which varies based upon corresponding variation of at least one particle characteristic of said particle; and

k. differentiating said particle based upon relative presence or absence of said at least one particle characteristic.

2. The method of flow cytometry as described in claim 1 , wherein said step of providing a variable volume container comprises the step of providing a flexible tubular body having an upper end and a lower end each hermetically formed.

3. The method of flow cytometry as described in claim 1 , wherein said step of providing a variable volume container having a flexible wall comprises the step of providing a container only a portion of which provides said flexible wall.

4. The method of flow cytometry as described in claim 1 , further comprising the step of generating a said fluid stream from the group consisting of: a fluid flowable in the flow path of said flow cytometer, a water, a buffer, a sheath fluid, a flow cytometer sheath fluid, a liquid reagent, a cleaning solutions, and a solvent.

5. The method of flow cytometry as described in claim 1 , where in said step of exerting an amount of pressure with an amount of gas on said flexible wall of said variable volume container further comprises selecting said amount of gas from the group consisting of an atmospheric gas, a mixture of gases, a mixture of gases having selected partial pressures, a purified gas, a nitrogen gas, a helium gas.

6. The method of flow cytometry as described in claim 1 , wherein said step of intermittently entraining a particle in said fluid stream in said flow path of said flow cytometer comprises intermittently entraining a particle in said fluid stream selected from the group consisting of a cell, a sperm cell, a labeled sperm cell, a stained sperm cell, a component obtained from a cell, a chromosome, a nucleic acid, a protein, a DNA, a RNA, a fragment of DNA, a fragment of RNA, and a fragment of protein.

7. The method of flow cytometry as described in claim 1 , further comprising the step of locating said variable volume container in a receptacle.

8. The method of flow cytometry as described in claim 7 , wherein said step of exerting an amount of pressure with an amount of a gas on an exterior surface of said flexible wall of said variable volume container further comprises the step of collecting said amount of gas between an interior surface of said receptacle and said exterior surface of said variable volume container.

9. The method of flow cytometry as described in claim 1 , wherein said step of illuminating said particle in said one of said plurality of droplets for a duration of time comprises the step of illuminating said particle in said one of said plurality of droplets with at least one laser beam.

10. The method of flow cytometry as described in claim 1 , wherein said step of detecting an emission generated by said particle which varies based upon corresponding variation of at least one particle characteristic of said particle comprises the step of detecting a fluorescent emission which varies based upon a difference in an amount of DNA within a cell.

11. The method of flow cytometry as described in claim 1 , further comprising the step of sorting said particle based upon relative presence or absence of said at least one particle characteristic.

12. The method of flow cytometry as described in claim 11 , wherein said step of sorting said particle based upon relative presence or absence of said at least one particle characteristic comprises the step of sorting X-chromosome bearing sperm cells from Y-chromosome bearing sperm cells.

13. The method of flow cytometry as described in claim 1 , further comprising the step of providing said flexible wall with at least two layers.

14. The method of flow cytometry as described in claim 13 , further comprising the step of providing a first layer compatible with said amount of gas and providing a second layer compatible with said fluid.

15. The method of flow cytometry as described in claim 14 , further comprising the step of collecting said amount of gas between said first layer and said second layer.

16. The method of flow cytometry as described in claim 15 , further comprising the step of bonding said first layer to said second layer.

17. The method of flow cytometry as described in claim 16 , wherein said first layer comprises a material selected from the group consisting of polypropylene, a polyethylene, a fluorocarbon, a styrene, and a polycarbonate.

18. The method of flow cytometry as described in claim 17 , wherein said second layer comprises a material selected from the group consisting of polypropylene, a polyethylene, a fluorocarbon, a styrene, and a polycarbonate.

19. The method of flow cytometry as described in claim 16 , further comprising providing at least one intermediate material layer between said first layer and said second layer.