Apparatus and method for performing electrodynamic focusing on a microchip

• US 5,858,187 A
• Filed: 09/26/1996
• Issued: 01/12/1999
• Est. Priority Date: 09/26/1996
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Energy Systems, Inc. (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Lockheed Martin Energy Systems, Inc. (French Alternative Energies and Atomic Energy Commission)
• Inventors: Ramsey, John Michael, Jacobson, Stephen C.
• Primary Examiner(s): Beisner, William H.
• Assistant Examiner(s): STARSIAK, JOHN S
• Application Number:
  US08/721,264
• Time in Patent Office: 838 Days
• Field of Search: 204/451, 204/452, 204/453, 204/454, 204/455, 204/601, 204/602, 204/603, 204/604, 204/605
• US Class Current: 204/452
• CPC Class Codes: B01F 33/30 Micromixers
• CPC Class Codes: B01F 33/3011 using a sheathing stream of a fluid surrounding a central stream of a different fluid, e.g. for reducing the cross-section of the central stream or to produce droplets from the central stream
• CPC Class Codes: B01F 33/3031 using electro-hydrodynamic [EHD] or electro-kinetic [EKI] phenomena to mix or move the fluids
• CPC Class Codes: G01N 15/149 specially adapted for sorting particles, e.g. by their size or optical properties
• CPC Class Codes: G01N 27/44773 Multi-stage electrophoresis, e.g. two-dimensional electrophoresis
• CPC Class Codes: G01N 30/6095 Micromachined or nanomachined, e.g. micro- or nanosize
• CPC Class Codes: Y10S 366/01 Micromixers: continuous laminar flow with laminar boundary mixing in the linear direction parallel to the fluid propagation with or without conduit geometry influences from the pathway

Abstract

A microchip device includes a focusing channel, in which an electric field strength established in the focusing channel is controlled relative to an electric field strength established in a material transport channel segment to spatially focus the material traversing the material transport channel segment.

Claims

1. A method of spatially altering material for determining a property or condition of said material, comprising the steps of:

applying a first electric potential to a material transport conduit, said applied first electrical potential inducing axially directed material transport;

applying a second electric potential to a focusing conduit which forms a confluence with the transport conduit, said applied second electrical potential inducing lateral spatial confinement of the transported material at the confluence; and

detecting a property or condition of the laterally spatially confined material.

2. A method according to claim 1, wherein the focusing conduit and the transport conduit are channels formed in a microchip, the focusing channel has first and second legs disposed on opposite sides of the transport channel and in opposing relation to each other, forming an intersection with said transport conduit, the second electric potential is applied to the first leg, and the method further includes applying a third electric potential to the second leg, the second and third electric potentials forming electric field vectors in general opposition to each other.

3. A method according to claim 1, wherein the focusing conduit and the transport conduit are channels which form an interconnected channel structure which includes a first reservoir, and a second reservoir, wherein the transport conduit is a first channel segment interconnecting the first and second reservoirs, a third reservoir, and a fourth reservoir, wherein the focusing conduit is a second channel segment interconnecting the third and fourth reservoirs and intersecting the first channel segment at an intersection, and the method further comprises the steps of applying electric potentials to the reservoirs to achieve lateral confinement, within the vicinity of the intersection, of the material transported through the first channel from the first reservoir.

4. A method according to claim 3, further comprising maintaining the electric potential at the intersection at a level lower than the potential at the first, third and fourth reservoirs and the second reservoir at a level lower than the potential at the intersection, said electrical potential levels effecting material transport in one direction from the first reservoir towards the second reservoir.

5. A method according to claim 1, wherein the transport conduit and the focusing conduit cross to form an intersection, and the method further comprises connecting a first reservoir to one end of the transport conduit, connecting a second reservoir to the opposite end of the transport conduit, connecting a third reservoir to one end of the focusing conduit, connecting a fourth reservoir to the opposite end of the focusing conduit, and applying electric potentials between at least two of the reservoirs to achieve lateral confinement, within the vicinity of the intersection, of the material transported through the transport conduit from the first reservoir.

6. A method according to claim 1, further comprising increasing the magnitude of the second electric potential relative to that of the first, said increased magnitude of the second electrical potential relative to the first electrical potential causing an increase in the degree of lateral confinement.

7. A method according to claim 1, wherein the first and second electric potentials impart at least one of electroosmotic flow and electrophoretic transport.

8. An apparatus for testing a sample of material comprising:

at least one transport conduit and at least one focusing conduit, said at least one focusing conduit forming a confluence with said at least one transport conduit; and

a voltage source for applying a first electric potential across said transport conduit and a second electric potential to said focusing conduit, said first electrical potential imparting axially directed material transport along said transport conduit and said second electrical potential imparting a lateral spatial confinement of the transported material at the confluence; and

a detector for detecting a property or condition of said laterally spatially confined material.

9. An apparatus according to claim 8, wherein said voltage source is operable to increase the magnitude of the second electric potential relative to that of the first electrical potential, said increased magnitude of the second electrical potential relative to the first electrical potential causing an increase in the degree of lateral spatial confinement.

10. An apparatus according to claim 8, wherein the transport conduit and the focusing conduit are part of an interconnected channel structure which includes a first reservoir, a second reservoir, a first channel segment interconnecting the first and second reservoirs, a third reservoir, a fourth reservoir, and a second channel segment interconnecting the third and fourth reservoirs and intersecting the first channel segment.

11. An apparatus according to claim 10, wherein said voltage source is operable to electrically ground the second reservoir.

12. An apparatus according to claim 10, wherein said voltage source is operable to maintain the potential at the intersection at a level lower than the potential at the first, third and fourth reservoirs and the second reservoir at a level lower than the potential at the intersection, said potential maintaining means effecting material transport in one direction from the first reservoir towards the second reservoir.

13. An apparatus according to claim 8, wherein the focusing conduit forms a T-intersection with the transport conduit.

14. An apparatus for testing a sample of material which comprises a microchip device comprising:

(i) a substrate having an interconnected channel structure formed thereon, the channel structure including a first reservoir, a second reservoir, a first channel segment interconnecting the first and second reservoirs, a third reservoir, a fourth reservoir, and a second channel segment interconnecting the third and fourth reservoirs and intersecting the first channel segment at a first intersection;

(ii) a cover plate bonded to the substrate over the interconnected channel structure;

(iii) means for applying voltages to the first, second, third and fourth reservoirs in relative magnitudes selected to laterally spatially confine material in one of the channel segments; and

a detector for detecting a property or condition of said laterally spatially confined material.

15. A microchip device according to claim 14, further comprising a fifth reservoir, a sixth reservoir, a third channel segment interconnecting the fifth and sixth reservoirs and intersecting the first channel segment between the first reservoir and the first intersection.

16. A method of testing a sample of material comprising the steps of:

placing the sample in a first reservoir which is connected to a second reservoir through a first channel;

placing a buffer material in a third reservoir which is connected to the first channel through a second channel;

placing a buffer material in a fourth reservoir which is connected to the first channel through a third channel disposed opposite the second channel, said first, second and third channels forming a four-way intersection;

applying voltages to the first, second, third, and fourth reservoirs to achieve lateral spatial confinement of the sample in the first channel;

exposing the spatially confined sample to electromagnetic energy whose interaction characteristics vary in accordance with at least one property or condition of the sample.

17. A method according to claim 16, wherein the exposing step comprises focusing a laser beam at a spot centered on the lateral spatial confinement of the sample, measuring at least one of the elastic or inelastic scattering, fluorescence, or absorbance attributable to interaction between the sample and the laser beam, and correlating characteristics of the light to at least one property or condition of the sample.

18. A method according to claim 17, wherein the sample material is a sample of biological cells.

19. An apparatus for sorting material comprising:

a microchannel structure having a material transport segment with a distal end in communication with a material reservoir, first and second focusing segments disposed on opposite sides of the transport segment, each having a distal end in communication with first and second focusing reservoirs, respectively, and a proximal end forming an intersection with a proximal end of the transport channel, and at least two sorting segments having proximal ends disposed in proximity to, and in fluid communication with, the intersection;

a voltage source for establishing a first electric field vector to axially transport material in the transport channel, and second and third electric field vectors to laterally confine and manipulate the material into one of the two sorting segments.

20. An apparatus according to claim 19, wherein the voltage source is operable to effect grounding of the receiving reservoir and electrical floating of the reservoir connected to the other sorting segment, said grounding and electrical floating of said reservoirs causing the manipulation of material into one of the two sorting segments.

21. An apparatus for manipulating a sample, comprising:

a plurality of spaced apart channels adapted to contain a fluid sample and having a common end terminating in a chamber;

a plurality of focusing channels alternatingly disposed on opposite sides of the sample channels and being adapted to contain a fluid buffer and having a common end terminating in the chamber; and

a voltage source for applying an electric potential to the focusing channels and the sample channels to impart axial motion of the sample towards the chamber and lateral spatial confinement of the sample in the chamber.