Microfluidic system including a bubble valve for regulating fluid flow through a microchannel

1. A method of making a bubble valve, comprising:

providing a microchannel having an interior bounded by a side wall, an aperture formed in the side wall and a valve chamber adjacent to the aperture in communication with the interior;

filling the microchannel with a liquid to form a meniscus of the liquid in the aperture, whereby the step of filling traps a gas in the valve chamber;

providing an actuator for increasing the pressure in the valve chamber to deflect the meniscus into the interior.

2. The method of claim 1 , wherein the step of providing an actuator comprises

applying and sealing an actuator comprising a chamber to a top surface of the microchannel to form a gas-filled chamber adjacent to the meniscus, wherein the actuator varies the pressure in the gas-filled chamber to deflect the meniscus into the interior, thereby regulating fluid flow.

3. A method of varying an electrical resistance in a microchannel, comprising the steps of:

generating a bubble by applying a pressure to a meniscus formed in a side wall of the microchannel, wherein the meniscus is formed by the liquid in the microchannel filling an aperture in the side wall;

injecting the bubble into a liquid in the microchannel, whereby the bubble varies the electrical resistance of the microchannel.

4. The method of claim 3 , wherein the step of applying a pressure comprises increasing the pressure within a sealed reservoir formed adjacent to the aperture.

5. A microfluidic device, comprising:

a microchannel having an interior bounded by a side wall;

a valve for regulating the flow of fluid through the microchannel, the valve comprising a gas-filled reservoir external to and in communication with the microchannel interior, a fluid meniscus interfacing the reservoir and the interior and an actuator for varying the volume of the reservoir to increase an internal pressure of the reservoir to vary the flow of liquid through the channel.

6. The microfluidic device of claim 1 , wherein the actuator deflects the meniscus into the microchannel interior to regulate the flow of fluid through the microchannel.

7. The microfluidic device of claim 1 , wherein the meniscus comprises a virtual wall formed in an aperture in the side wall of the microchannel when the microchannel is filled with a liquid.

8. The microfluidic device of claim 1 , wherein the actuator generates a gas bubble in the microchannel.

9. The microfluidic device of claim 8 , further comprising a hydrophobic patch attached to an inner wall of the microchannel for anchoring the gas bubble.

10. The microfluidic device of claim 8 , wherein the microchannel defines a cavity for retaining the gas bubble.

11. The microfluidic device of claim 1 , wherein the gas filled reservoir comprises a movable membrane.

12. The microfluidic device of claim 11 , wherein the actuator deflects the movable membrane to create a bubble in the microchannel interior.

13. A microfluidic device comprising:

a first plate having a groove formed therein defining a microchannel;

a second plate for enclosing the microchannel bonded to the first plate having an aperture adjacent to the groove sized and dimensioned to form a meniscus when the microchannel is filled with a liquid, the aperture defining a reservoir adjacent to the microchannel, wherein the meniscus forms an interface between the microchannel and the reservoir; and

a flexible membrane bonded to the second plate to seal the reservoir and defining a movable wall of the reservoir.

14. The microfluidic device of claim 13 , further comprising an actuator for deflecting the flexible membrane, wherein the deflection of the membrane increases the pressure in the reservoir and deflects the meniscus into the microchannel to regulate liquid flow therethrough.

15. The microfluidic device of claim 13 , further comprising a hydrophobic patch attached to the groove.

16. The microfluidic device of claim 13 , wherein the meniscus forms a bubble in the microchannel to block liquid flow.

17. An electrophoretic system, comprising

a first electrokinetically operated microchannel;

a sample well for providing a sample to the first electrokinetically operated microchannel microchannel;

a voltage source;

a bubble valve for injecting a bubble into the microchannel to vary the electrical resistance of the microchannel.

18. The electrophoretic system of claim 17 , further comprising:

a second electrokinetically operated microchannel in communication with the first electrokinetically operated microchannel, wherein the

a bubble valve selectively blocks flow from the first electrokinetically operated microchannel to the second electrokinetically operated microchannel by selectively injecting a bubble into a microchannel.