Microfluidic system including a virtual wall fluid interface port for interfacing fluids with the microfluidic system

1. A method of labeling a sample, comprising:

conveying the sample through a channel having a first virtual wall fluid interface port, the first virtual wall fluid interface port comprising a first opening formed in a side wall of the channel, the first opening sized and dimensioned such that a fluid within the channel forms a virtual wall in the first opening to define the first virtual wall fluid interface port;

separating the sample in the channel into a plurality of bands; and

injecting a labeling solution through the first virtual wall fluid interface port, wherein the labeling solution interacts with one of said bands to form a labeled band.

2. The method of claim 1 , further comprising the step of detecting the labeled band.

3. The method of claim 1 , further comprising the step of ejecting at least a portion of the labeled band from the channel.

4. The method of claim 3 , wherein the step of ejecting a portion of the labeled band comprises ejecting at least a portion of the labeled band through a second virtual wall interface port in the form of one or more droplets, the second virtual wall fluid interface port comprising a second opening formed in a side wall of the channel, the second opening sized and dimensioned such that a fluid within the channel forms a virtual wall in the second opening to define the second virtual wall fluid interface port.

5. The method of claim 1 , wherein the labeling solution comprises a labeled species and a binding molecule for binding to a selected band and the labeled species.

6. The method of claim 5 , wherein the step of injecting the labeling solution comprises injecting the labeled species through the first virtual wall fluid interface port and injecting the binding molecule through a second virtual wall fluid interface port, the second virtual wall fluid interface port comprising a second opening formed in a side wall of the channel, the second opening sized and dimensioned such that a fluid within the channel forms a virtual wall in the second opening to define the second virtual wall fluid interface port.

7. The method of claim 1 , wherein the virtual wall fluid interface port has a diameter between about 25 μm and about 100 μm, such that when a fluid is disposed in the interior of the channel, the fluid forms a virtual wall at the virtual wall fluid interface port.

8. The method of claim 1 , further comprising the step of separating the plurality of bands in to a plurality of sub-bands.

9. The method of claim 1 , further comprising the step of transferring a labeled band to one of a MALDI-MS system and a multi-well plate for further analysis.

10. A method of labeling a sample, comprising:

conveying the sample through a channel having a virtual wall fluid interface port, the virtual wall fluid interface port comprising an opening formed in a side wall of the channel, the opening sized and dimensioned such that a fluid within the channel forms a virtual wall in the opening to define the virtual wall fluid interface port; and

injecting a labeling solution through the virtual wall fluid interface port, wherein the labeling solution interacts with the sample to label the sample.

11. The method of claim 10 , further comprising the step of separating the sample into a plurality of bands.

12. The method of claim 4 , wherein the step of ejecting employs a pressure pulse generator, said pressure pulse generator comprising a conical-shaped pressure chamber disposed opposite the second virtual wall fluid interface port and in communication with the interior of the channel and a piezo-actuated membrane connected to the pressure chamber.

13. The method of claim 4 , wherein the step of ejecting employs a pin assembly comprising a first pin and a second pin spaced from the first pin to define a capillary for receiving a liquid volume.