Microfluidic devices

1. A method of mixing solutions comprising:

a) providing a microfluidic device comprising:

(i) a first microfluidic channel comprising a first pump and a first solution;

(ii) a second microfluidic channel comprising a second, opposing pump and a second solution; and

(iii) a third microfluidic channel,

wherein each pump comprises an inlet valve, a pump valve and an outlet valve, and the first, second and third channels intersect at a common junction that is not a valve; and

b) performing a pumping cycle comprising:

(i) opening the inlet valves and closing the outlet valves;

(ii) opening the pump valves, wherein the first and second solutions are pumped into the pump valves;

(iii) closing the inlet valves and opening the outlet valves; and

(iv) closing the pump valves, wherein the solutions in the pump valves are pumped into the third channel in laminar flow and wherein opening the outlet valves and closing the pump valves results in back and forth movement of the solutions, wherein the solutions are mixed.

2. The method of claim 1 wherein the structure is comprised on a microchip.

3. The method of claim 1 wherein the first channel is connected to a port that holds the first solution and the second channel is connected to a port that holds the second solution.

4. The method of claim 1 wherein the first solution comprises an analyte and the second fluid comprises a reagent.

5. The method of claim 1 further comprising repeating step (b).

6. The method of claim 1 wherein the third channel comprises a serpentine area.

7. The method of any of claims 1 - 6 wherein the microfluidic device comprises a fluidic layer, a deformable membrane layer and a pneumatic layer, wherein each valve in the device comprises the deformable membrane layer sitting against a valve seat in the fluidic layer to close a fluidic path between microfluidic channels in the fluidic layer, and the pneumatic layer comprises a pneumatic displacement chamber opposite the membrane and connected to a vacuum or pressure source and wherein applying vacuum or pressure to the membrane layer deforms the deformable membrane, thereby opening or closing the valve.

8. The method of claim 7 wherein the pneumatic displacement chamber is connected to a vacuum source and wherein applying vacuum to the membrane layer deforms the deformable membrane, thereby opening the valve.

9. The method of claim 7 wherein the valves comprise vias in the fluidic layer.

10. The method of claim 7 wherein the fluidic layer and the actuation layer comprise glass wafers into which channels are etched.

11. A method of mixing solutions comprising:

a) providing a microfluidic device comprising a router comprising:

(i) a first microfluidic channel comprising a first valve and a first port comprising a first solution;

(ii) a second microfluidic channel comprising a second valve and a second port comprising a gas;

(iii) a third microfluidic channel comprising a third valve and a third port comprising a second solution;

(iv) a fourth microfluidic channel comprising a fourth valve; and

(v) a reaction chamber

wherein the first, second, third and fourth channels connect to a central diaphragm valve and the fourth channel connects with the reaction chamber;

b) pumping the first and second solutions from the first and third ports and air from the second port into the reaction chamber to form boluses separated by air, wherein mixing of the solutions is aided by the back and forth movement of the two solutions into the second channel during multiple pumping steps.

12. The method of claim 11 wherein the microfluidic device is comprised on a microchip.

13. The method of claim 11 wherein the first solution comprises an analyte and the second solution comprises a reagent.

14. The method of claim 11 wherein the gas is air.

15. The method of any of claims 11 , 12 , 13 and 14 wherein the microfluidic device comprises a fluidic layer, a deformable membrane layer and a pneumatic layer, wherein each valve in the device comprises the deformable membrane layer sitting against a valve seat in the fluidic layer to close a fluidic path between microfluidic channels in the fluidic layer, and the pneumatic layer comprises a pneumatic displacement chamber opposite the membrane and connected to a vacuum or pressure source and wherein applying vacuum or pressure to the membrane layer deforms the deformable membrane, thereby opening or closing the valve.

16. The method of claim 15 wherein the pneumatic displacement chamber is connected to a vacuum source and wherein applying vacuum to the membrane layer deforms the deformable membrane, thereby opening the valve.

17. The method of claim 15 wherein the valves comprise vias in the fluidic layer.

18. The method of claim 15 wherein the fluidic layer and the actuation layer comprise glass wafers into which channels are etched.