System and method for processing fluid in a fluidic cartridge

1. A valve system in a fluidic cartridge for metering a liquid sample in a sample processing region, comprising:

a fluid pathway for passing a liquid sample therethrough from an upstream end to a downstream end;

a sample processing chamber within the fluid pathway having an inlet valve upstream of the sample processing chamber and an outlet valve downstream of the sample processing chamber;

a downstream sample processing region within the fluid pathway downstream of the outlet valve; and

a bypass channel coupled to the fluid pathway at a junction between the outlet valve and the downstream sample processing region, the valve system configured such that surplus liquid sample downstream of the outlet valve may be evacuated through the bypass channel when the outlet valve is closed, thereby leaving a metered volume of liquid sample in the fluid pathway between the inlet valve and the downstream sample processing region; and

wherein the fluid pathway further comprises a compressible element downstream of the downstream sample processing region, the compressible element being configured to become increasingly biased against fluid upstream of the compressible element as the liquid sample passes through the open outlet valve so as to increase the pressure in the fluid pathway, such that the surplus liquid sample downstream of the outlet valve may be expelled from the fluid pathway and into the bypass channel by the compressible element when the outlet valve is closed and whilst the pressure in the bypass channel is less than the pressure in the fluid pathway, and wherein the compressible element is a gas spring comprising a blind bore filled with a compressible fluid.

2. The valve system of claim 1 , wherein the downstream sample processing region comprises a target chamber.

3. The valve system of claim 1 , further comprising:

a plurality of fluid pathways, each for passing a liquid sample through from an upstream end to a downstream end;

a sample processing chamber within each fluid pathway and each having an inlet valve upstream of the sample processing chamber and an outlet valve downstream of the sample processing chamber;

a downstream sample processing region within each fluid pathway downstream of the respective outlet valve; and

a bypass channel coupled to each fluid pathway at a junction between the downstream sample processing region and the outlet valve therein, the valve system configured such that surplus liquid sample downstream of the outlet valve may be evacuated through the respective bypass channel when the outlet valve is closed, thereby leaving a plurality of metered volumes of liquid sample in the plurality of fluid pathways between the respective inlet valve and the respective downstream sample processing regions.

4. A valve system in a fluidic cartridge for expelling liquid sample from a sample processing region, comprising:

a fluid pathway for passing a liquid sample therethrough from an upstream end to a downstream end;

an outlet valve within the fluid pathway, the outlet valve configured to move between a closed position in which it prevents the liquid sample from passing through the outlet valve and an open position in which it permits the liquid sample to pass through the outlet valve;

a downstream sample processing region within the fluid pathway downstream of the outlet valve;

a bypass channel coupled to the fluid pathway at a junction between the outlet valve and the downstream sample processing region, the valve system configured such that liquid sample downstream of the outlet valve may be expelled through the bypass channel when the outlet valve is in its closed position; and

at least one compressible element downstream of the downstream sample processing region, the at least one compressible element configured to become increasingly biased against fluid upstream of the compressible element as the liquid sample passes through the open outlet valve, such that the liquid sample downstream of the outlet valve may be expelled from the fluid pathway and into the bypass channel by the at least one compressible element when the outlet valve is closed, wherein the at least one compressible element is a gas spring comprising a blind bore filled with a compressible fluid.

5. The valve system of claim 4 , further comprising a sample processing chamber within the fluid pathway and upstream of the outlet valve.

6. The valve system of claim 1 , further comprising a bypass valve located within the bypass channel, the bypass valve configured to move between a closed position in which it prevents the liquid sample from passing through the bypass valve and an open position in which it permits the liquid sample to pass through the bypass valve.

7. The valve system of claim 1 , wherein at least one of the valves in the valve system is a pneumatically-actuated valve.

8. The valve system of claim 7 , wherein the at least one pneumatically-actuated valve comprises a valve chamber having first and second openings connected to the fluidic pathway or bypass channel, respectively; and

a flexible membrane movable between a closed position, in which the flexible membrane seals against the first and second openings to prevent fluid flow through the fluidic pathway or bypass channel, and an open position, in which the flexible membrane is spaced apart from the first and second openings to permit fluid to flow through the fluidic pathway or bypass channel.

9. The valve system of claim 8 , further comprising a pneumatic interface for connecting to a source of positive and/or gauge gas pressure, the pneumatic interface comprising a plurality of ports.

10. The valve system of claim 9 , wherein the at least one pneumatically-actuated valve further comprises a fluid passageway having an opening in the valve chamber, the opening separated from the first and second openings by the flexible membrane, wherein the fluid passageway is coupled to a port in the pneumatic interface for applying a positive or negative gas pressure in the valve chamber to move the flexible membrane between the open and closed positions.

11. The valve system of claim 7 , wherein the inlet and outlet valves are configured to be actuated simultaneously.

12. The valve system of claim 1 , wherein the bypass channel is connected to the fluid pathway immediately downstream of the outlet valve to as to minimise or eradicate a deadleg between the outlet valve and the bypass channel.

13. The valve system of claim 3 , wherein the sample processing chamber is a nucleic acid amplification chamber; wherein the downstream sample processing region is a detection chamber; and wherein ratio of detection chambers to nucleic acid amplification chambers is 2:1.

14. The valve system of claim 3 , wherein each downstream sample processing region is coupled to a single compressible element.

15. The valve system of claim 8 , wherein the valve chamber is formed in a first polymer layer and the first polymer layer is a pneumatic interface of the fluidic cartridge.

16. The valve system of claim 1 , wherein the fluid pathway is formed in a second polymer layer, and the second polymer layer is a fluidic layer of the fluidic cartridge.

17. The valve system of claim 16 , wherein the bypass channel is formed in the second polymer layer.

18. The valve system of claim 8 , wherein the flexible membrane comprises a thermoplastic elastomer.

19. The valve system of claim 15 , wherein the first polymer layer comprises polypropylene.

20. The valve system of claim 16 , wherein the second polymer layer comprises polypropylene.

21. A method of metering a liquid sample in a fluidic cartridge comprising a fluid pathway having a sample processing chamber therein, an inlet valve upstream of the sample processing chamber and an outlet valve downstream of the sample processing chamber, a downstream sample processing region therein, and at least one compressible element downstream of the downstream sample processing region, and a bypass channel coupled to the fluid pathway at a junction between the outlet valve and the downstream sample processing region; the method comprising:

passing a liquid sample through the inlet valve, into the sample processing chamber, and through the outlet valve, wherein the compressible element compresses as the liquid sample passes downstream of the outlet valve;

closing the inlet and outlet valves;

evacuating surplus liquid sample downstream of the outlet valve through the bypass channel to empty the fluid pathway downstream of the outlet valve of fluid, thereby leaving a metered volume of liquid sample in the fluid pathway between the inlet valve and the downstream sample processing region; and

opening the outlet valve and delivering the metered volume of liquid sample to the downstream sample processing region,

wherein the evacuation of the surplus liquid sample comprises exerting, by the compressible element, a force against the surplus liquid sample to expel it from the fluid pathway and into the bypass channel.

22. The method of claim 21 , wherein the fluidic cartridge further comprises a bypass valve in the bypass channel, and wherein the method further comprises:

closing the bypass valve prior to the step of passing a liquid sample through the inlet valve, into the first chamber, and through the outlet valve; and wherein the step of evacuating surplus liquid sample downstream of the outlet valve further comprises opening the bypass valve.

23. The method of claim 21 , wherein the step of closing the inlet and outlet valves comprises closing the inlet and outlet valves simultaneously.

24. A method of expelling surplus liquid sample from a fluidic cartridge comprising a fluid pathway having a sample processing chamber therein, an inlet valve upstream of the sample processing chamber and an outlet valve downstream of the sample processing chamber, and a downstream sample processing region therein downstream of the outlet valve, a bypass channel coupled to the fluid pathway at a junction between the outlet valve and the downstream sample processing region, and a compressible element downstream of the downstream sample processing region; the method comprising:

passing a liquid sample through the outlet valve, thereby compressing the compressible element as the liquid sample passes downstream of the outlet valve; and

closing the outlet valve and evacuating surplus liquid sample downstream of the outlet valve through the bypass channel by the compressible element exerting a force against the surplus liquid sample to expel it from the fluid pathway and into the bypass channel.

25. The method of claim 24 , wherein the fluidic cartridge further comprises a bypass valve in the bypass channel, and wherein the method further comprises:

closing the bypass valve prior to the step of passing a liquid sample through the outlet valve;

and wherein the step of evacuating surplus liquid sample downstream of the outlet valve further comprises opening the bypass valve.