Valve which depressurises, and a valve system

1. A fluidic cartridge comprising a fluid sample processing region formed by

a network of channels, the network of channels fluidly connected to a first channel for introducing a fluid sample into the network of channels; and

a valve system for depressurising the fluid sample processing region, the valve system comprising:

an isolation valve between the first channel and the network of channels, the isolation valve actuatable to seal off the network of channels and thereby create a closed system therein, and

a control valve interrupting a second channel within the network of channels, the control valve having a valve chamber coupled to the second channel via first and second openings, the valve chamber configured such that it has a first volume when the control valve is closed to prevent fluid from flowing between the first and second openings, and a second, larger, volume when the control valve is open to permit fluid to flow between the first and second openings;

wherein the valve system is operable to depressurise the fluid sample processing region by closing the control valve to decrease the total volume within the network of channels, actuating the isolation valve to seal off the network of channels and thereby create a closed system within the network of channels, and opening the control valve to increase the total volume within the closed system of the network of channels.

2. The fluidic cartridge of claim 1 , wherein the network of channels further comprises:

a fluid pathway for receiving and processing a fluid sample introduced by the first channel, the fluid pathway having an upstream end at the isolation valve and a downstream end, the downstream end being closed;

wherein the second channel is a bypass channel for removing excess fluid sample from the fluid pathway, the bypass channel coupled to the fluid pathway at a junction partway along the fluid pathway and coupled to the first channel upstream of the junction and downstream of the isolation valve.

3. The fluidic cartridge of claim 1 , wherein the control valve further comprises:

a valve cavity and a flexible membrane within the valve cavity, the flexible membrane having a first portion actuatable to seal against the first opening and a second portion actuatable to seal against the second opening;

wherein the valve chamber is formed between the flexible membrane and the valve cavity; and

wherein the valve chamber is configured such that the first portion may be actuated independently of the second portion to enable the first opening to be sealed after the second opening.

4. The fluidic cartridge of claim 1 , wherein the network of channels further comprises:

first and second fluid pathways for receiving and processing a fluid sample introduced by the first channel, the first and second fluid pathways each having an upstream end at the isolation valve and a downstream end, the downstream end being closed; wherein

the second channel is a bypass channel for removing excess fluid sample from the first and second fluid pathways, the bypass channel comprising:

a first bypass portion coupled to the first fluid pathway at a junction partway along the first fluid pathway;

a second bypass portion coupled to the second fluid pathway at a junction partway along the second fluid pathway; and

wherein the first and second bypass portions are coupled to the first channel upstream of the respective junctions and downstream of the isolation valve.

5. The fluidic cartridge of claim 4 , wherein the valve chamber further comprises:

a third opening, wherein the control valve is coupled to:

the first channel upstream of the junction and downstream of the isolation valve via the first opening;

the first bypass portion via the second opening; and

the second bypass portion via the third opening; and

a flexible membrane overlying the valve chamber, the flexible membrane having a first portion actuatable to seal against the first opening and a second portion actuatable to seal against the second and third openings;

wherein the valve chamber is configured such that the first portion may be actuated independently of the second portion to enable the first opening to be sealed after the second and third openings'.

6. The fluidic cartridge of claim 1 , wherein the valve chamber is formed in a first polymer layer, wherein the first polymer layer is a pneumatic layer of the fluidic cartridge.

7. The fluidic cartridge of claim 1 , wherein the network of channels is formed in a second polymer layer, wherein the second polymer layer is a fluidic layer of the fluidic cartridge.

8. The fluidic cartridge of claim 6 , wherein the first polymer layer comprises polypropylene.

9. The fluidic cartridge of claim 7 , wherein the second polymer layer comprises polypropylene.