Smart disposable plastic lab-on-a-chip for point-of-care testing

• US 20050130292A1
• Filed: 09/22/2004
• Published: 06/16/2005
• Est. Priority Date: 09/26/2003
• Status: Active Grant

• Current Assignee: University of Cincinnati
• Original Assignee: University of Cincinnati
• Inventors: Choi, Jin-Woo, Nevin, Joseph, Ahn, Chong H., Beaucage, Gregory
• Granted Patent: US 7,524,464 B2
• Time in Patent Office: Days
• US Class Current: 435/287.100
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

Disclosed herein is a fully-integrated, disposable biochip for point-of-care testing of clinically relevant parameters. Specifically, in accordance with an embodiment of the present invention, the biochip is designed for POCT (point-of-care-testing) of an array of metabolic parameters including partial pressure of oxygen, Glucose, and Lactate concentration from venous blood samples. The biochip is fabricated on a low-cost plastic substrate using mass manufacturing compatible fabrication processes. Furthermore, the biochip contains a fully-integrated metallic micro-needle for blood sampling. The biochip also uses smart passive microfluidics in conjunction with low-power functional on-chip pressure generators for microfluidic sequencing. The design, configuration, assembly and operation of the biochip are ideally suited for a disposable biochip specifically targeted towards POCT applications.

Claims

1. A disposable, integrated biochip for clinical diagnostic applications, said biochip comprising:

a micro-needle for sampling a fluid from a subject;

at least one micro-sensor for sensing at least one relevant parameter of said sampled fluid; and

a passive micro-fluidic control system, connecting said micro-needle to said at least one micro-sensor, to accept said sampled fluid from said micro-needle and to facilitate movement of said sampled fluid to said at least one micro-sensor.

2. The biochip of claim 1 further comprising a micro-propulsion system connecting to said passive micro-fluidic control system to move said sampled fluid through said passive micro-fluidic control system.

3. The biochip of claim 1 further comprising a micro-calibration system connected to said at least one micro-sensor to calibrate said biochip to environmental conditions at a time when said biochip is used.

4. The biochip of claim 3 wherein said at least one micro-sensor, said passive micro-fluidic control system, said micro-propulsion system, and said micro-calibration system are collectively fabricated on at least two plastic substrates that are integrated together within said biochip.

5. The biochip of claim 1 wherein said micro-needle is metallic.

6. The biochip of claim 1 wherein said at least one micro-sensor comprises at least one of an electro-chemical oxygen biosensor, an electrochemical glucose biosensor, an electro-chemical lactate biosensor, a pH biosensor, and a hematocrit biosensor.

7. The biochip of claim 1 wherein said passive micro-fluidic system comprises:

a micro-dispenser reservoir;

at least one passive micro-valve;

at least one micro-sensor reservoir connecting to said at least one micro-sensor via at least one semi-permeable membrane of said at least one micro-sensor; and

at least two micro-fluidic channels connecting together said micro-dispenser reservoir, said at least one passive micro-valve, and said at least one micro-sensor reservoir.

8. The biochip of claim 2 wherein said micro-propulsion system comprises:

at least one micro-chamber containing a pressurized gas and being connected to said passive micro-fluidic control system; and

at least one micro-heater positioned next to and being in contact with a thermo-plastic membrane of said micro-chamber to release said pressurized gas into an air inlet of said passive micro-fluidic control system upon melting of said thermo-plastic membrane by said micro-heater when an electrical pulse is applied to said micro-heater.

9. The biochip of claim 2 wherein said micro-propulsion system comprises:

at least one micro-heater; and

at least one solid chemical propellant positioned on said at least one micro-heater to release an inert gas into an air inlet of said passive micro-fluidic control system upon activation of said at least one solid chemical propellant by said micro-heater when an electrical pulse is applied to said micro-heater.

10. The biochip of claim 3 wherein said micro-calibration system comprises:

a calibration solution pouch containing a calibration buffer of at least one know concentration of at least one analyte;

at least one micro-fluidic channel, connecting to said calibration solution pouch, to carry said calibration buffer to said at least one micro-sensor when said calibration solution pouch is ruptured; and

at least one waste reservoir to accept said calibration buffer after said biochip is calibrated.

11. The biochip of claim 10 wherein said calibration solution pouch is metallic to minimize diffusion of gases to and from an environment that could alter said at least one known concentration of said calibration buffer.

12. The biochip of claim 4 wherein said at least two plastic substrates comprises at least one of cyclic olefin copolymer, polyimide, polymethylmethaacrylate, PDMS, polyethylene, and polycarbonate.

13. The biochip of claim 6 wherein said oxygen biosensor comprises:

a semi-permeable membrane that is permeable to at least oxygen molecules;

a solid, gel-based layer of electrolyte solution being in contact with said semi-permeable membrane; and

at least two electrodes being in contact with said solid, gel-based layer of electrolyte solution.

14. The biochip of claim 6 wherein said glucose biosensor comprises:

a first semi-permeable membrane that is permeable to at least glucose molecules;

a glucose oxidase enzyme layer being in contact with said first semi-permeable membrane to oxidize said glucose molecules into at least oxygen molecules;

a second semi-permeable membrane being in contact with said glucose oxidase enzyme layer and being permeable to at least said oxygen molecules;

a solid, gel-based layer of electrolyte solution being in contact with said second semi-permeable membrane; and

at least two electrodes being in contact with said solid, gel-based layer of electrolyte solution.

15. The biochip of claim 6 wherein said lactate biosensor comprises:

a first semi-permeable membrane that is permeable to at least lactate molecules;

a lactate oxidase enzyme layer being in contact with said first semi-permeable membrane to oxidize said lactate molecules into at least oxygen molecules;

a second semi-permeable membrane being in contact with said lactate oxidase enzyme layer and being permeable to at least said oxygen molecules;

a solid, gel-based layer of electrolyte solution being in contact with said second semi-permeable membrane; and

at least two electrodes being in contact with said solid, gel-based layer of electrolyte solution.

16. The biochip of claim 1 further comprising at least two conductive traces connected to said at least one micro-sensor for monitoring an electric current generated by said micro-sensor.

17. The biochip of claim 1 wherein said at least one relevant parameter comprises at least one of partial oxygen concentration, glucose level, lactate level, pH, and hematocrit.

18. A method to fabricate a disposable, integrated biochip for clinical diagnostic applications, said method comprising:

fabricating a micro-needle for sampling a fluid from a subject;

fabricating at least one micro-sensor, a passive micro-fluidic control system, a micro-propulsion system, and a micro-calibration system on at least two plastic substrates;

integrating said micro-needle and said at least two plastic substrates into a single biochip structure.

19. The method of claim 18 wherein said fabricating said micro-needle includes using at least a micro-machining technique on a metallic sample.

20. The method of claim 18 wherein said fabricating said at least one micro-sensor includes using at least one of a film evaporation technique, an electroplating technique, a spray coating technique, and a lithography/screen printing technique.

21. The method of claim 18 wherein said fabricating said passive micro-fluidic control system, said micro-propulsion system, and said micro-calibration system on said at least two plastic substrates includes using at least one of a plastic micro-injection molding technique, a laser micro-machining technique, and a UV-LIGA lithography technique.

22. The method of claim 18 wherein said integrating said micro-needle and said at least two plastic substrates includes using at least plastic-to-plastic direct bonding techniques.

23. The method of claim 22 wherein said plastic-to-plastic direct bonding techniques include at least one of a low deformation thermoplastic fusion bonding technique and a room temperature ultraviolet-adhesive bonding technique.

24. The method of claim 18 wherein said passive micro-fluidic control system is connected between said micro-needle and said at least one micro-sensor such that said passive micro-fluidic control system may accept said sampled fluid from said micro-needle and facilitate movement of said sampled fluid to said at least one micro-sensor.

25. The method of claim 18 wherein said micro-propulsion system is connected to said passive micro-fluidic control system to move said sampled fluid through said passive micro-fluidic control system via the release of a pressurized inert gas from said micro-propulsion system into an air inlet of said passive micro-fluidic control system.

26. The method of claim 18 wherein said micro-calibration system is connected to said at least one micro-sensor to deliver a calibration buffer solution to said at least one micro-sensor to facilitate calibrating said biochip to environmental conditions at a time when said biochip is used.

27. The method of claim 21 wherein said laser micro-machining technique is used to at least create a groove in at least one of said at least two plastic substrates for said micro-needle to be locked into by a plastic-to-plastic direct bonding technique.

28. The method of claim 18 wherein fabricating said micro-sensor comprises:

depositing two electrodes onto one of said at least two plastic substrates;

screen printing a first conductive trace onto said one of said at least two plastic substrates such that said first conductive trace electrically connects to a first electrode of said two electrodes;

screen printing a second conductive trace onto said one of said at least two plastic substrates such that said second conductive trace electrically connects to a second electrode of said two electrodes;

spray coating a solid, gel-based electrolyte layer onto said two electrodes; and

spray coating a semi-permeable oxygen membrane layer onto said solid, gel-based electrolyte layer.

29. The method of claim 28 wherein depositing said two electrodes comprises:

evaporating gold film onto said one of said at least two plastic substrates to pattern a first electrode and a second electrode; and

electroplating said gold film of said first electrode with a thin layer of silver.

30. The method of claim 28 further comprising:

screen printing a glucose oxidase enzyme layer onto said semi-permeable oxygen membrane layer; and

spray coating a semi-permeable glucose membrane layer onto said glucose oxidase enzyme layer.

31. The method of claim 28 further comprising:

screen printing a lactate oxidase enzyme layer onto said semi-permeable oxygen membrane layer; and

spray coating a semi-permeable lactate membrane layer onto said glucose oxidase enzyme layer.

32. The method of claim 18 wherein fabricating said micro-propulsion system includes:

patterning a micro-heater onto one of said at least two plastic substrates using lithography/screen printing techniques; and

patterning a solid chemical propellant onto said micro-heater using lithography/screen printing techniques.

33. The method of claim 18 wherein fabricating said micro-propulsion system includes:

sealing a compressed gas within a micro-chamber between two of said at least two plastic substrates using a thermoplastic fusion bonding technique such that said micro-chamber includes a thin thermoplastic membrane; and

patterning a micro-heater onto said thermoplastic membrane using lithography/screen printing techniques.

34. The method of claim 18 wherein fabricating said micro-calibration system includes:

sealing a calibration solution pouch between two of said at least two plastic substrates using at least a plastic-to-plastic direct bonding technique, wherein said calibration solution pouch contains a calibration buffer of at least one known concentration of at least one analyte;

fabricating at least one micro-fluidic channel on at least one of said at least two plastic substrates, using at least a plastic micro-injection molding technique, such that said at least one micro-fluidic channel may carry said calibration buffer to said at least one micro-sensor; and

fabricating at least one waste reservoir on at least one of said at least two plastic substrates, using said plastic micro-injection molding technique, such that said waste reservoir may accept said calibration buffer after said biochip is calibrated.

35. The method of claim 18 wherein fabricating said passive micro-fluidic control system includes:

fabricating a micro-dispenser reservoir on at least one of said at least two plastic substrates using at least one of a plastic micro-injection molding technique and a UV-LIGA technique;

fabricating at least one passive micro-valve on at least one of said at least two plastic substrates using at least one of a plastic micro-injection molding technique and a UV-LIGA technique;

fabricating at least one micro-sensor reservoir, on at least one of said at least two plastic substrates using at least one of a plastic micro-injection molding technique and a UV-LIGA technique, such that said at least one micro-sensor reservoir connects to said at least one micro-sensor via at least one semi-permeable membrane of said at least one micro-sensor; and

fabricating at least two micro-fluidic channels, on at least one of said at least two plastic substrates using at least one of a plastic micro-injection molding technique and a UV-LIGA technique, such that said at least two micro-fluidic channels connect together said micro-dispenser reservoir, said at least one passive micro-valve, and said at least one micro-sensor reservoir.

36. The method of claim 32 further comprising screen printing a conductive trace onto said one of said at least two plastic substrates such that said conductive trace electrically connects to said micro-heater, wherein an electrical pulse may be applied to said micro-heater via said conductive trace.

37. The method of claim 33 further comprising screen printing a conductive trace onto said thermoplastic membrane such that said conductive trace electrically connects to said micro-heater, wherein an electrical pulse may be applied to said micro-heater via said conductive trace.

38. The method of claim 18 wherein said at least two plastic substrates comprises at least one of cyclic olefin copolymer (COC), polyimide, polymethylmethaacrylate, PDMS, polyethylene, and polycarbonate.

39. A method to use and read a disposable, integrated biochip for clinical diagnostic applications, said method comprising:

injecting a micro-needle of said biochip into a subject to obtain a micro-sample of fluid from said subject;

inserting said biochip, containing said micro-sample of fluid, into a bio-socket of a bio-analyzer; and

initiating a sensing sequence of said bio-analyzer to measure at least one relevant parameter of said micro-sample of fluid.

40. The method of claim 39 wherein said subject is a human and said micro-sample of fluid is blood.

41. The method of claim 39 wherein injecting said micro-needle causes a micro-dispenser reservoir within said biochip to be filled with a predetermined volume of said micro-sample of fluid.

42. The method of claim 39 wherein inserting said biochip results in:

sealing an input of said micro-needle to prevent backflow of said fluid; and

breaking a calibration solution pouch within said biochip such that a calibration buffer contained within said pouch flows out of said pouch and fills at least one sensing reservoir within said biochip.

43. The method of claim 39 wherein initiating said sensing sequence results in:

calibrating said biochip to current environmental conditions by measuring said at least one relevant parameter of a calibration buffer, being of known concentration of said at least one relevant parameter, within at least one sensing reservoir of said biochip,;

flushing said calibration buffer from said at least one sensing reservoir into at least one waste reservoir of said biochip;

propelling said micro-sample of fluid from a micro-dispenser reservoir within said biochip to said at least one sensing reservoir within said biochip via at least one micro-fluidic channel within said biochip;

measuring said at least one relevant parameter of said micro-sample of fluid; and

displaying said at least one relevant parameter of said micro-sample of fluid on a display of said bio-analyzer.

44. The method of claim 39 wherein said at least one relevant parameter comprises at least one of partial oxygen concentration, glucose level, lactate level, pH, and hematocrit.

45. The method of claim 39 wherein said bio-analyzer comprises:

said bio-socket;

timing and sequence control circuitry for controlling said sensing sequence;

bio-sensor detection circuitry for electronically detecting said at least one relevant parameter;

a user interface for operating said bio-analyzer;

a display for presenting said measured at least one relevant parameter to an operator of said bio-analyzer; and

at least one power source for supplying electrical power to at least said timing and sequence control circuitry, said bio-sensor detection circuitry, said user interface, and said display.

46. The method of claim 45 wherein said timing and sequence control circuitry sends at least one electrical pulse to a micro-propulsion system of said biochip to cause said micro-sample of fluid to be transported from a micro-dispenser reservoir within said biochip to at least one sensing reservoir within said biochip.

47. The method of claim 45 wherein said timing and sequence control circuitry sends at least one electrical pulse to a micro-propulsion system of said biochip to cause a calibration buffer to be transported from at least one sensing reservoir within said biochip to at least one waste reservoir within said biochip.

48. The method of claim 45 wherein said bio-sensor detection circuitry detects at least on electrical current produced by at least one micro-sensor within said biochip such that said at least one electrical current is proportional to said at least one relevant parameter of said micro-sample of fluid.

49. The method of claim 45 wherein said bio-sensor detection circuitry detects at least on electrical current produced by at least one micro-sensor within said biochip such that said at least one electrical current is proportional to said at least one relevant parameter of a calibration buffer within said biochip.

50. The method of claim 45 wherein said user interface comprises at least one control switch