Small volume liquid handling apparatus and method

1. A fluid dispensing system comprising:

a fluid container;

a dispensing head in fluid communication with the fluid container;

a displacement mechanism which delivers fluid from the fluid container to the dispensing head such that an aliquot of liquid is delivered to a distal end of the dispensing head where the aliquot of liquid is retained due to surface tension between the liquid and the distal end of the dispensing head; and

a pressurized gas displacement mechanism which delivers an aliquot of gas to the distal end of the dispensing head which causes the aliquot of liquid retained at the distal end of the dispensing head to separate from the distal end of the dispensing head;

wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head and a needle positioned within the lumen that extends beyond the distal end of the lumen, the needle forming the distal end of the dispensing head where the aliquot of liquid is retained.

2. A fluid dispensing system according to claim 1 wherein the displacement mechanism is a mechanical displacement mechanism.

3. A fluid dispensing system according to claim 1 wherein the displacement mechanism is selected from the group consisting of a syringe, a pump, an electrophoretic device and a mechanical displacement device.

4. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism delivers the aliquot of gas to the aliquot of liquid to cause the aliquot of liquid to separate from the distal end of the dispensing head.

5. A fluid dispensing system according to claim 1 wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head.

6. A fluid dispensing system according to claim 1 wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head and a gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

7. A fluid dispensing system according to claim 6 wherein the lumen is surrounded by an outer gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

8. A fluid dispensing system according to claim 1 wherein the dispensing head further defines a gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

9. A fluid dispensing system according to claim 1 wherein the aliquot of liquid dispensed has a volume of less than 1 microliter.

10. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism controls the energy supplied by the aliquot of gas within a range of 0.001 W to 100 W.

11. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism controls the weight of the aliquot of gas released within a range of 10 −10 to about 10 −4 kg.

12. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism controls the pressure of the aliquot of gas released within a range of 0.05 psi to 50 psi.

13. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism causes the aliquot of liquid to be dispensed without aerating the aliquot of liquid.

14. A fluid dispensing system according to claim 1 wherein the fluid dispensing system further comprises a pressurized gas source regulated by a flow valve to the dispensing head.

15. A fluid dispensing system according to claim 14 wherein the fluid dispensing system further comprises a controller that actuates the flow valve to release a discontinuous aliquot of gas.

16. A fluid dispensing system according to claim 1 wherein the fluid dispensing system further includes a controller coupled to actuate a gas supply coupled to the pressurized gas displacement mechanism.

17. A fluid dispensing system according to claim 1 wherein the pressurized gas displacement mechanism comprises a solenoid valve.

18. A fluid dispensing system according to claim 1 wherein the fluid dispensing system further includes a controller coupled to actuate a solenoid valve of the pressurized gas displacement mechanism.

19. A fluid dispensing system according to claim 1 wherein the fluid dispensing system further includes a controller comprising a timer circuit which times operation of the pressurized gas displacement mechanism relative to operation of the displacement mechanism.

20. A fluid dispensing system according to claim 1 wherein the fluid dispensing system further includes a controller comprising a timer circuit which operates the pressurized gas displacement mechanism to release an aliquot of gas after operation of the displacement mechanism.

21. A fluid dispensing system according to claim 1 wherein the fluid dispensing system comprises a plurality of dispensing heads mounted to a mounting block which comprises gas supply bores for supplying gas to each of the plurality of dispensing heads.

22. A fluid dispensing system according to claim 1 wherein the fluid dispensing system comprises at least one gas control solenoid coupled between the displacement mechanism and the pressurized gas displacement mechanism.

23. A fluid dispenser head comprising: a dispensing head through which an aliquot of liquid is delivered to a distal end of the dispensing head where the aliquot of liquid is retained due to surface tension between the liquid and the distal end of the dispensing head; and a pressurized gas displacement mechanism which delivers an aliquot of gas to the distal end of the dispensing head which causes the aliquot of liquid retained at the distal end of the dispensing head to separate from the distal end of the dispensing head, wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head and a needle positioned within the lumen that extends beyond the distal end of the lumen, the needle forming the distal end of the dispensing head where the aliquot of liquid is retained.

24. A fluid dispenser head according to claim 23 wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head.

25. A fluid dispenser head according to claim 24 wherein the lumen is surrounded by an outer gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

26. A fluid dispenser head according to claim 23 wherein the dispensing head defines a lumen through which the aliquot of liquid is delivered to the distal end of the dispensing head and a gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

27. A fluid dispenser head according to claim 23 wherein the dispensing head further defines a gas housing through which the aliquot of gas is delivered to the distal end of the dispensing head.

28. A fluid dispenser head according to claim 23 wherein the aliquot of liquid dispensed has a volume of less than 1 microliter.

29. A fluid dispenser head according to claim 23 wherein the pressurized gas displacement mechanism controls the energy supplied by the aliquot of gas within a range of 0.001 W to 100 W.

30. A fluid dispenser head according to claim 23 wherein the pressurized gas displacement mechanism controls the weight of the aliquot of gas released within a range of 10 −10 to about 10 −4 kg.

31. A fluid dispenser head according to claim 23 wherein the pressurized gas displacement mechanism controls the pressure of the aliquot of gas released within a range of 0.05 psi to 50 psi.

32. A fluid dispenser head according to claim 23 wherein the pressurized gas displacement mechanism causes the aliquot of liquid to be dispensed without aerating the aliquot of liquid.