Microfluidic devices, systems and methods for performing integrated reactions and separations

• US 20030138359A1
• Filed: 02/06/2003
• Published: 07/24/2003
• Est. Priority Date: 06/08/1998
• Status: Abandoned Application

• Current Assignee: Caliper Life Sciences Incorporated (Revvity, Inc.)
• Original Assignee: Caliper Holdings Incorporated
• Inventors: Chow, Andrea W., Parce, J. Wallace, Kopf-Sill, Anne R., Sundberg, Steven A.
• Application Number:
  US10/359,961
• Publication Number:
  US 20030138359A1
• Time in Patent Office: Days
• US Class Current: 422/101
• CPC Class Codes: B01F 33/30 Micromixers
• CPC Class Codes: B01L 2200/0605 Metering of fluids
• CPC Class Codes: B01L 2200/0673 Handling of plugs of fluid surrounded by immiscible fluid
• CPC Class Codes: B01L 2300/0816 Cards, e.g. flat sample carriers usually with flow in two horizontal directions
• CPC Class Codes: B01L 2300/0864 comprising only one inlet and multiple receiving wells, e.g. for separation, splitting
• CPC Class Codes: B01L 2300/0867 Multiple inlets and one sample wells, e.g. mixing, dilution
• CPC Class Codes: B01L 2300/087 Multiple sequential chambers
• CPC Class Codes: B01L 2400/0415 electrical forces, e.g. electrokinetic
• CPC Class Codes: B01L 2400/0418 electro-osmotic flow [EOF]
• CPC Class Codes: B01L 2400/0421 electrophoretic flow
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 3/50273 characterised by the means or forces applied to move the fluids micropumps F04B19/006, of the membrane type F04B43/043
• CPC Class Codes: B01L 3/502753 characterised by bulk separation arrangements on lab-on-a-chip devices, e.g. for filtration or centrifugation separation in general B01D; microapparatus for analysis using electrophoresis G01N27/44791; sample preparation G01N1/28
• CPC Class Codes: B01L 3/502784 specially adapted for droplet or plug flow, e.g. digital microfluidics automatic analysis using a stream of discrete samples in a tube system G01N35/08
• CPC Class Codes: G01N 2001/4038 electric methods, e.g. electromigration, electrophoresis, ionisation
• CPC Class Codes: G01N 27/44743 Introducing samples
• CPC Class Codes: G01N 27/44791 Microapparatus sample containers with integrated microfluidic structures B01L3/5027
• CPC Class Codes: Y10T 436/117497 with a continuously flowing sample or carrier stream
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

Microfluidic devices for performing integrated reaction and separation operations. The devices comprise a planar substrate having a first surface with an integrated channel network disposed therein. The reaction region in the integrated microscale channel network has a mixture of at least first and second reactants located therein, wherein the mixture interacts to produce one or more products. The reaction region is configured to maintain contact between the first and second reactants contained within it. The device also includes a separation region in the integrated channel network, where the separation region is configured to separate the first reactant from the product, when the first reactant and product are flowing through the separation region.

Claims

1. A microfluidic device for performing integrated reaction and separation operations, comprising:

a body structure having an integrated microscale channel network disposed therein;

a reaction region within the integrated microscale channel network, the reaction region having a mixture of at least first and second reactants disposed in and flowing through the reaction region, the mixture interacting to produce one or more products, wherein the reaction region is configured to maintain contact between the first and second reactants flowing therethrough; and

a separation region in the integrated channel network, the separation region in fluid communication with the reaction region and being configured to separate the first reactant from the one or more products flowed therethrough.

2. The microfluidic device of claim 1, wherein the reaction region comprises a microscale reaction channel having first and second ends and the separation region comprises a microscale separation channel having first and second ends.

3. The microfluidic device of claim 2, wherein the reaction channel and the separation channel are in fluid communication and cross at a first intersection between the first and second ends of the reaction channel and the separation channel, respectively.

4. The microfluidic device of claim 3, further comprising an electrokinetic material transport system operably coupled to the first and second ends of the reaction channel and the first and second ends of the separation channel for electrokinetically transporting material through the reaction channel and into the separation channel.

5. The microfluidic device of claim 4, wherein at least two of the first and second reactants and product have different electrophoretic mobilities under an applied electric field.

6. The microfluidic device of claim 4, wherein the reaction channel comprises first and second fluid regions disposed therein, the first fluid region comprising the first and second reactants and the product, and having a first conductivity, the first fluid region being bounded by the second fluid regions, wherein the second fluid regions have a second conductivity that is lower than the first conductivity.

7. The microfluidic device of claim 3, wherein the separation channel comprises a separation inducing buffer, the separation inducing buffer having a conductivity that is higher than the second conductivity.

8. The microfluidic device of claim 3, wherein the separation channel comprises a separation inducing buffer, the separation inducing buffer having a conductivity that is lower than the first conductivity.

9. The microfluidic device of claim 3, wherein the separation channel comprises a separation inducing buffer, the separation inducing buffer having a conductivity that is the same as the first conductivity.

10. The microfluidic device of claim 3, further comprising:

at least first and second conductivity measuring electrodes disposed in electrical contact with opposite sides of the reaction channel adjacent to the first intersection; and

a conductivity detector operably coupled to the first and second conductivity measuring electrodes.

11. The microfluidic device of claim 3, further comprising at least a third reactant in the reaction region, the second and third reactants interacting to produce the product, and wherein the first reactant comprises a test compound.

12. The microfluidic device of claim 3, wherein the separation channel comprises a separation medium disposed therein.

13. The microfluidic device of claim 3, further comprising:

a source of at least first reactant in fluid communication with the reaction channel; and

a source of at least second reactant in fluid communication with the reaction channel.

14. The microfluidic device of claim 13, wherein the source of at least first reactant comprises at least a first reactant reservoir connected to the reaction channel via a first reactant channel, and the source of at least second reactant comprises:

a source of at least a second reactant separate from the body structure; and

an external sample accessing capillary in fluid communication with the reaction channel, for contacting the second reactant reservoir and transporting a volume of the second reactant into the reaction channel.

15. The microfluidic device of claim 13, wherein the source of at least first reactant comprises a first reactant reservoir disposed in the body structure and connected to the reaction channel via a first reactant channel, and the source of second reactant comprises a second reactant reservoir disposed in the body structure and connected to the reaction channel via a second reactant channel.

16. The microfluidic device of claim 3, wherein the body structure comprises at least first and second planar substrates, a plurality of grooves being fabricated into a first planar surface of the first substrate, and a first planar surface of the second substrate being mated to the first planar substrate of the first substrate covering the plurality of grooves and defining the integrated channel network.

17. The microfluidic device of claim 16, wherein at least one of the first and second substrates comprise a silica-based substrate.

18. The microfluidic device of claim 17, wherein the silica-based substrate is selected from glass, quartz, fused silica, or silicon.

19. The microfluidic device of claim 18, wherein the silica based substrate comprises glass.

20. The microfluidic device of claim 16, wherein at least one of the first and second substrates comprises a polymeric material.

21. The microfluidic device of claim 20, wherein the polymeric material is selected from polymethylmethacrylate, polycarbonate, polytetrafluoroethylene, polyvinylchloride, polydimethylsiloxane, polysulfone, polystyrene, polymethylpentene, polypropylene, polyethylene, polyvinylidine fluoride, and acrylonitrile-butadiene-styrene copolymer.

22. The microfluidic device of claim 21, wherein the polymeric material comprises polymethylmethacrylate.

23. The microfluidic device of claim 3, wherein channels in the integrated channel network have at least one cross-sectional dimension between about 0.1 and about 500 μ

m.

24. The microfluidic device of claim 3, wherein channels in the integrated channel network have at least one cross-sectional dimension between about 1 and about 100 μ

m.

25. The microfluidic device of claim 24, wherein channels in the integrated channel network have at least one cross-sectional dimension between about 10 and about 100 μ

m.

26. The microfluidic device of claim 2, wherein the reaction channel comprises alternating first and second fluid regions, the first region having a higher ionic concentration than the second fluid region, the reaction mixture being localized in a first fluid region.

27. The microfluidic device of claim 2, wherein the reaction channel and the separation channel are in fluid communication via a connecting channel, the connecting channel intersecting the reaction channel between the first and second ends of the reaction channel, and intersecting the separation channel between the first and second ends of the separation channel.

28. The microfluidic device of claim 27, further comprising an electrokinetic material transport system operably coupled to the first and second ends of the reaction channel and the first and second ends of the separation channel for electrokinetically transporting material through the reaction channel and into the separation channel.

29. The microfluidic device of claim 28, wherein at least two of the first and second reactants and product have different electrophoretic mobilities under an applied electric field.

30. The microfluidic device of claim 27, wherein the connecting channel comprises a smaller cross-sectional area than the first or second channels.

31. The microfluidic device of claim 27, wherein the connecting channel comprises a length less than about 1 mm.

32. The microfluidic device of claim 27, wherein the connecting channel comprises a length less than about 0.5 mm.

33. The microfluidic device of claim 32, wherein the reaction channel comprises first and second fluid regions disposed therein, the first fluid region comprising the first and second reactants and the product, and having a first conductivity, the first fluid region being bounded by the second fluid regions, wherein the second fluid regions have a second conductivity that is lower than the first conductivity.

34. The microfluidic device of claim 32, wherein the separation channel comprises a separation inducing buffer, the separation inducing buffer having a conductivity that is higher than the second conductivity.

35. The microfluidic device of claim 34, wherein the separation inducing buffer comprises a conductivity that is from about 2 to about 100 times greater than the second conductivity.

36. The microfluidic device of claim 34, wherein the separation inducing buffer has a conductivity that is lower than the first conductivity.

37. The microfluidic device of claim 34, wherein the separation inducing buffer comprises a conductivity that is from about 2 to about 100 times less than the first conductivity.

38. The microfluidic device of claim 34, wherein the separation inducing buffer has a conductivity approximately equal to the first conductivity.

39. The microfluidic device of claim 27, further comprising:

at least first and second conductivity measuring electrodes disposed in electrical or capacitive contact with opposite sides of the reaction channel adjacent to the first intersection; and

a conductivity detector operably coupled to the first and second conductivity measuring electrodes.

40. The microfluidic device of claim 27, further comprising at least a third reactant in the reaction channel, the second and third reactants interacting to produce the product, and wherein the first reactant comprises a test compound.

41. The microfluidic device of claim 27, wherein the separation channel comprises a separation medium disposed therein.

42. The microfluidic device of claim 27, wherein the reaction region comprises alternating first and second fluid regions, the first region having a higher ionic concentration than the second fluid region, the reaction mixture being localized in a first fluid region.

43. The microfluidic device of claim 2, wherein the first end of the reaction channel is in fluid communication with the first end of the separation channel at a first junction, and further comprising a buffer channel having first and second ends, the first end of the buffer channel in fluid communication with the reaction channel and the separation channel at the first junction, the second end of the buffer channel being in fluid communication with a source of separation inducing buffer.

44. The microfluidic device of claim 43, wherein the first and second channel portions are co-linear.

45. The microfluidic device of claim 43, further comprising an electrokinetic material transport system operably coupled to the second ends of the reaction channel, the separation channel and the buffer channel for electrokinetically transporting material from the reaction region to the separation region, and for introducing separation inducing buffer into the separation channel from the buffer channel.

46. The microfluidic device of claim 45, wherein at least two of the first and second reactants and product have different electrophoretic mobilities under an applied electric field.

47. The microfluidic device of claim 43, wherein the reaction channel comprises first and second fluid regions disposed therein, the first fluid region comprising the first and second reactants and the product, and having a first conductivity, the first fluid region being bounded by the second fluid regions, wherein the second fluid regions have a second conductivity that is lower than the first conductivity.

48. The microfluidic device of claim 43, wherein the separation inducing buffer has a conductivity that is greater than the second conductivity.

49. The microfluidic device of claim 48, wherein the separation inducing buffer has a conductivity that is from about 2 to about 100 times greater than the second conductivity.

50. The microfluidic device of claim 48, wherein the separation inducing buffer has a conductivity that is lower than the first conductivity.

51. The microfluidic device of claim 48, wherein the separation inducing buffer has a conductivity that is from about 2 to about 100 times less than the first conductivity.

52. The microfluidic device of claim 48, wherein the separation inducing buffer has a conductivity that is approximately equal to the first conductivity.

53. The microfluidic device of claim 48, wherein the separation inducing buffer has a conductivity that is approximately equal to the second conductivity.

54. The microfluidic device of claim 43, further comprising at least a third reactant in the reaction region, the second and third reactants interacting to produce the product, and wherein the first reactant comprises a test compound.

55. The microfluidic device of claim 43, wherein the separation channel comprises a separation medium disposed therein.

56. The microfluidic device of claim 43, wherein the reaction region comprises alternating first and second fluid regions, the first region having a higher ionic concentration than the second fluid region, the reaction mixture being localized in a first fluid region.

117. Use of a device selected from any one of the devices of claims 1-64 and 92-100 for practicing a method selected from any one of the methods of claims 65-91 and 101-114.

57. A microfluidic device for performing integrated reaction and separation operations, comprising:

a body structure;

a first channel disposed in the body structure, the first channel having disposed therein, at least first and second fluid regions, the first fluid region having an ionic concentration higher than an ionic concentration of the second fluid region, and the first and second fluid regions communicating at a first fluid interface;

second and third channels disposed in the body structure, the second channel intersecting and connecting the first and third channels at intermediate points along a length of the first and third channels, respectively;

an electrokinetic material transport system for applying a voltage gradient along a length of the first channel, but not the second channel, to electrokinetically move the first fluid interface past the intermediate point of the first channel, and force at least a portion of the first fluid regions through the second channel into the third channel.

58. The device of claim 57, wherein the first fluid region has a conductivity that is from about 2 to about 200 times greater than a conductivity of the second fluid regions.

59. The device of claim 57, wherein the first fluid region has a conductivity that is from about 2 to about 100 times greater than a conductivity of the second fluid regions.

60. The device of claim 57, wherein the first fluid region has a conductivity that is from about 2 to about 50 times greater than a conductivity of the second fluid regions.

61. The device of claim 57, wherein the first fluid region has a conductivity that is from about 2 to about 20 times greater than a conductivity of the second fluid regions.

62. The device of claim 57, wherein the first fluid region has a conductivity that is from about 2 to about 10 times greater than a conductivity of the second fluid regions.

63. The device of claim 57, wherein the first fluid region comprises at least first and second materials.

64. The device of claim 63, wherein the first and second materials have different electrophoretic mobilities under an applied electric field.

65. A method of performing integrated reaction and separation operations, comprising:

providing a microfluidic device comprising a body structure having a reaction channel and a separation channel disposed therein, the reaction channel and separation channel being in fluid communication;

flowing at least first and second reactants through the reaction channel in a first fluid region, the first and second reactants interacting to form at least a first product within the first fluid region, wherein the step of transporting through the first channel is carried out under conditions for maintaining the first and second reactants and products substantially within the first fluid region;

directing at least a portion of the first fluid region to the separation channel, the separation channel being configured to separate the product from at least one of the first and second reactants; and

transporting the portion along the separation channel to separate the product from at least first reactant.

66. The method of claim 65, wherein:

the flowing step comprises applying a first voltage gradient along the reaction channel to electrokinetically move the first fluid region into the intersection; and

the directing step comprises applying a second voltage gradient along the separation channel to direct at least a portion of the first fluid region into the separation channel;

the separating step comprises applying a third voltage gradient along the separation channel to separate the first reactant from the first product.

67. The method of claim 66, wherein the conditions suitable for maintaining the first and second reactant and product substantially within the first fluid region comprises the first fluid region having a first conductivity and being bounded by second fluid regions having a second conductivity that is lower than the first conductivity.

68. The method of claim 66, wherein the first conductivity is from about 2 to about 100 times greater than the second conductivity.

69. The method of claim 66, wherein the separation channel has a separation inducing buffer disposed therein, the separation buffer having a conductivity lower than the first conductivity.

70. The method of claim 66, wherein the separation channel has a separation inducing buffer disposed therein, the separation inducing buffer having a conductivity approximately equivalent to the first conductivity.

71. The method of claim 66, wherein the product and at least one of the first and second reactants have different electrophoretic mobilities under an applied electric field.

72. The method of claim 65, further comprising the step of detecting the separated product in the separation channel.

73. The method of claim 65, wherein:

in the providing step, the reaction channel and the separation channel disposed in the body structure are in fluid communication and cross at a first intersection;

the flowing step comprises flowing the first fluid region into the first intersection; and

the directing step comprises directing the portion of the first mixture in the intersection into the separation channel.

74. The method of claim 73, further comprising the step of detecting when the first fluid region is disposed in the intersection.

75. The method of claim 74, wherein the step of detecting when the first fluid region is disposed in the intersection comprises detecting a change in conductivity of fluid at the intersection.

76. The method of claim 74, wherein the first and second fluid regions have optical characteristics that are distinguishable from each other, and the step of detecting when the first fluid region is disposed in the intersection comprises detecting within the intersection, the optical characteristics indicating the presence of the first fluid region.

77. The method of claim 74, wherein the optical characteristics that are distinguishable from each other comprise a fluorophore or chromophore disposed within at least one of the first or second fluid regions.

78. The method of claim 77, wherein the optical characteristics that are distinguishable from each other comprise a first chromophore or fluorophore disposed in the first fluid region and a second chromophore or fluorophore disposed in the second fluid region, the first fluorophore or chromophore being distinguishable from the second chromophore or fluorophore.

79. The method of claim 69, wherein:

in the providing step, the reaction channel and the separation channel are in fluid communication via a connecting channel the connecting channel intersecting the reaction channel at a first intersection and intersecting the separation channel at a second intersection;

the flowing step comprises flowing the first fluid region into the first intersection; and

the directing step comprises directing at least a portion of the first fluid region through the connecting channel into the separation channel.

80. The method of claim 79, wherein the directing step comprises providing a voltage gradient between the reaction channel and separation channel to electrokinetically direct a portion of the first fluid region from the reaction channel, through the connecting channel and into the separation channel.

81. The method of claim 79, wherein the directing step comprises flowing the first fluid region along the reaction channel through the first intersection, a pressure differential present at an interface of the first and second fluid regions forcing a portion of the first fluid region into the connecting channel and into the separation channel.

82. The method of claim 69, wherein:

in the providing step, the reaction channel has first and second ends, the separation channel has first and second ends, the first end of the reaction channel being in fluid communication with the first end of the separation channel at a first junction, and further comprising a buffer channel having first and second ends, the first end of the buffer channel in fluid communication with the reaction channel and separation channel at the first junction;

the flowing step comprises flowing the first fluid region along the reaction channel to the first junction; and

the directing step comprises directing the portion of the first mixture in the intersection into the separation channel.

83. The method of claim 82, wherein the directing step comprises directing at least a portion of the first fluid region into the separation channel while concomitantly injecting the separation inducing buffer from the third channel into the separation channel.

84. A method of directing fluid transport in a microscale channel network, comprising:

providing a microfluidic device having at least first and second intersecting channels disposed therein, the first channel being intersected by the second channel at an intermediate point;

introducing first and second fluid regions into the first channel, wherein the first and second fluid regions are in communication at a first fluid interface, and wherein the first fluid region has a higher conductivity than the second fluid region;

applying an electric field across a length of the first channel, but not across the second channel, to electroosmotically transport the first and second fluid regions through the first channel past the intermediate point, whereby a portion of the first fluid is forced into the second channel.

85. A method of transporting materials in an integrated microfluidic channel network, comprising:

providing a first microscale channel that is intersected at an intermediate point, by a second channel;

introducing first and second fluid regions serially into the first channel, the first and second fluid regions being in communication at a first fluid interface;

applying a motive force to the first and second fluid regions to move the first and second fluid regions past the intermediate point, the first and second fluid regions having different flow rates under said motive force, the different flow rates producing a pressure differential at the first interface, the pressure differential resulting in a portion of the first material being injected into the second channel.

86. The method of claim 86, wherein the motive force comprises an electric field applied across a length of the first channel.

87. A method of performing integrated reaction and separation operations in a microfluidic system, comprising:

providing a microfluidic device comprising a body, and a reaction channel and a separation channel disposed therein, the reaction channel being in fluid communication with the separation channel;

transporting at least first and second reactants through the first region, the first and second reactants are maintained substantially together allowing reactants to interact to form at least a first product in the first mixture;

transporting the first mixture including the product to the second region wherein the product is separated from at least one of the reactants; and

separating the product from at least one of the reactants.

88. A method of performing integrated reaction and separation operations in a microfluidic system, comprising:

providing a microfluidic device having at least first and second channel regions disposed therein, the first and second channel regions being connected by a first connecting channel;

introducing first reactants into the first channel region, the first reactants being contained within a first material region having a first ionic concentration, the first region being bounded by second regions having a second ionic concentration, the second ionic concentration being lower than the first ionic concentration;

transporting the first and second material regions past an intersection of the first channel region and the first connecting channel, whereby at least a portion of the first material region is diverted through the connecting channel and into the second channel region.

89. A method of performing integrated reaction and separation operations in a microfluidic device, comprising:

providing a microfluidic device having a reaction channel portion and a separation channel portion, the reaction channel portion being fluidly connected and intersecting the separation channel portion at a first intersection;

transporting at least a first reactant through the reaction channel portion within a first discrete fluid region, under conditions whereby the reactant reacts to produce at least a first product, within the first fluid region, the first fluid region being bounded by at least a second fluid region;

detecting when the at least first fluid region reaches the first intersection;

injecting a portion of the at least first fluid region into the separation channel;

separating the product from the at least first reactant.

90. The method of claim 89, wherein the first fluid region has a conductivity higher than the second fluid region, and the detecting step comprises detecting a change in conductivity in the first intersection when the first fluid region reaches the first intersection.

91. The method of claim 89, wherein at least one of the first and second fluid regions comprises a marker compound, and the detecting step comprises detecting when the marker compound is present in the first intersection.

92. A microfluidic device for performing integrated reaction and separation operations, comprising:

a body structure having an integrated microscale channel network disposed therein;

a reaction region within the integrated microscale channel network, the reaction region having a mixture of at least a first reactant and a first product disposed in and flowing through the reaction region, wherein the reaction region is configured to maintain contact between the first reactant and the first product flowing therethrough; and

a separation region in the integrated channel network, the separation region in fluid communication with the reaction region and being configured to separate the first reactant from the first product flowed therethrough.

93. A microfluidic device for analyzing electrokinetic mobility shifts of analytes, comprising:

a body structure;

a first microfluidic channel portion having substantially no electrical field applied across its length;

a second microfluidic channel portion having an electrical field applied across its length, the second channel portion being fluidly connected to the first channel portion; and

a pressure source in communication with at least one of the first channel portion and the second channel portion for moving a material through the first channel portion into the second channel portion.

94. The microfluidic device of claim 93, comprising first and second electrodes in electrical contact at first and second ends of the second channel portion, respectively, each of the first and second electrodes being operably coupled to an electrical power source, for applying the electric field across the length of the second channel portion.

95. The microfluidic device of claim 93, wherein the pressure source is a positive pressure source and is operably coupled to the first channel portion.

96. The microfluidic device of claim 93, wherein the pressure source comprises a negative pressure source, and is operably coupled to the second channel portion, for drawing the analytes from the first channel portion into the second channel portion.

97. The microfluidic device of claim 93, wherein the first channel portion is fluidly connected to a source of first and second analytes.

98. The microfluidic device of claim 93, wherein the first channel portion is fluidly connected to a source of at least a third analyte.

99. The microfluidic device of claim 98, further comprising a capillary element extending out of the body structure, which capillary element includes a capillary channel disposed therein, the capillary channel being open at a first end and fluidly connected to the first channel portion at a second end, and wherein fluid communication between the first channel portion and the source of at least a third analyte is provided by contacting the open end of the capillary channel with a source of the third analyte.

100. The microfluidic device of claim 99, wherein the first and second electrodes are disposed in electrical contact with third and fourth channels that are in fluid communication with the second channel portion at the first and second ends of the second channel portion, respectively.

101. A method of analyzing an effect of a first analyte on a second analyte, comprising:

contacting the first analyte with the second analyte in a first microfluidic channel portion having substantially no electric field applied across its length;

transporting at least a portion of the first analyte and second analyte to a second channel portion that is in fluid communication with the first channel portion and which has an electric field applied across its length;

measuring a change, if any, in an electrokinetic mobility of the second analyte in the second channel portion, a change in the electrokinetic mobility of the second analyte being indicative of an effect of the first analyte on the second analyte.

102. The method of claim 101, wherein the effect of the first analyte on the second analyte is a binding of the first analyte to the second analyte, which results in a change of the electrokinetic mobility of the second analyte.

103. The method of claim 101, wherein the effect of the first analyte on the second analyte is a cleavage effect, which results is a change in an electrokinetic mobility of the second analyte.

104. The method of claim 101, further comprising:

contacting the first and second analytes in the first channel with a third analyte; and

measuring a change in the electrokinetic mobility of the second analyte in the presence of the third analyte relative to a change in the electrokinetic mobility of the second analyte in the absence of the third analyte.

105. The method of claim 101, wherein the second analyte has a detectable label associated with it.

106. The method of claim 105, wherein the detectable label comprises an optically detectable label.

107. The method of claim 106, wherein the optically detectable label comprises a fluorescent label.

108. The method of claim 101, wherein the first ad second analytes are transported into the second microfluidic channel portion by applying a pressure differential between the first channel portion and the second channel portion

109. A method of analyzing an electrokinetic mobility shift in a first analyte, comprising:

flowing the first analyte through a first microscale channel portion having substantially no electrical field applied across it;

introducing the first analyte into a second microfluidic channel portion;

applying an electric field across a length of the second microfluidic channel portion but not the first microfluidic channel portion;

measuring an electrokinetic mobility of the first analyte under the electric field applied in the second channel portion.

110. The method of claim 109, wherein the first analyte comprises a product of an interaction between at least first and second precursor analytes, the first and second precursor analytes having a first and second electrokinetic mobilities, respectively, and the first analyte having a third electrokinetic mobility.

111. The method of claim 110, wherein third electrokinetic mobility is different from at least one of the first and second electrokinetic mobilities.

112. The method of claim 111, wherein the first precursor analyte comprises a detectable label, the detectable label becoming part of the first analyte when the first and second precursor analytes interact.

113. The method of claim 112, wherein the second electrokinetic mobility is different from the first electrokinetic mobility.

114. The method of claim 113, wherein the first and second precursor analytes are moved from the first channel portion to the second channel portion by applying a pressure differential between the first and second channel portions to force the first and second precursor analytes into the second channel portion.

115. Use of a microfluidic device for performing integrated reaction and separation operations, the device comprising:

a body structure having an integrated microscale channel network disposed therein;

a reaction region within the integrated microscale channel network, the reaction region having a mixture of at least first and second reactants disposed in and flowing through the reaction region, the mixture interacting to produce one or more products, wherein the reaction region is configured to maintain contact between the first and second reactants flowing therethrough; and

a separation region in the integrated channel network, the separation region in fluid communication with the reaction region and being configured to separate the first reactant from the one or more products flowed therethrough.

118. An assay utilizing a use set forth in any one of claims 115-117.

116. Use of a microfluidic device for performing integrated reaction and separation operations, the device comprising:

a body structure having an integrated microscale channel network disposed therein;

a reaction region within the integrated microscale channel network, the reaction region having a mixture of at least a first reactant and a first product disposed in and flowing through the reaction region, wherein the reaction region is configured to maintain contact between the first reactant and the first product flowing therethrough; and

,

a separation region in the integrated channel network, the separation region in fluid communication with the reaction region and being configured to separate the first reactant from the first product flowed therethrough.