Particle impedance sensor

• US 6,703,819 B2
• Filed: 12/03/2001
• Issued: 03/09/2004
• Est. Priority Date: 12/03/2001
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Gascoyne, Peter, Anderson, Tom, Vykoukal, Jody, Becker, Frederick
• Primary Examiner(s): HE, AMY
• Application Number:
  US10/005,373
• Publication Number:
  US 20030102854A1
• Time in Patent Office: 827 Days
• Field of Search: 324/71.4, 324/71.1, 324/713, 324/691, 324/698, 324/715, 738/655, 738/66, 204/450, 204/547, 209/12.2, 209/127.1, 209/128, 209/212
• US Class Current: 324/71.4
• CPC Class Codes: G01N 15/13 Details pertaining to apertures
• CPC Class Codes: G01N 2015/1027 Determining speed or velocity of a particle
• CPC Class Codes: G01N 2015/1029 Particle size
• CPC Class Codes: G01N 2015/135 Electrodes

Abstract

Apparatuses and methods for analyzing particles using an impedance sensor. A flow-through impedance sensor may use two in-line electrodes driven in counter phase. A common sensor electrode may be used to, for example, detect impedance and determine trajectories through the sensor area. The sensor may be used in a wide variety of applications, including but not limited to use with microfluidic devices for determining particle characteristics such as position, velocity, size, and concentration as well as detection of bacterial spores and other biological agents of potential use in warfare and bio-terrorism.

Claims

1. A impedance sensor comprising:

a sensor electrode;

first and second driver electrodes coupled to the sensor electrode and driven in counter phase to produce a net output signal of about zero at the sensor electrode; and

a fluid channel defined through the sensor electrode and the first and second driver electrodes.

2. The impedance sensor of claim 1, wherein the sensor electrode comprises copper.

3. The impedance sensor of claim 1, wherein the sensor electrode comprises a first and second dielectric membrane sandwiching a detector electrode.

4. The impedance sensor of claim 3, wherein the first or second dielectric membrane comprises polyimide.

5. The impedance sensor of claim 3, wherein the first or second dielectric membrane is laminated.

6. The impedance sensor of claim 3, wherein the first and second driver electrodes contact the first and second dielectric membranes, respectively.

7. The impedance sensor of claim 1, wherein the first and second driver electrodes are driven at multiple frequencies.

8. The impedance sensor of claim 1, wherein the first and second driver electrodes are driven with an alternating current signal.

9. The impedance sensor of claim 1, wherein the cross section of the channel is rectangular.

10. The impedance sensor of claim 1, further comprising a programmable fluid processor coupled to the sensor electrode.

11. A flow-through impedance sensor, comprising:

a fluid channel for transporting a carrier medium and particles through the impedance sensor;

a composite membrane sensor assembly coupled to the channel and comprising a detector electrode sandwiched between first and second dielectric membranes;

first and second driver electrodes coupled to the channel and positioned adjacent opposite sides of the composite membrane sensor assembly, the first and second driver electrodes being driven in counter phase to produce;

(a) a net output signal of about zero at the detector electrode when no particle is within the impedance sensor; and

(b) a non-zero net output signal at the detector electrode when a particle is within the impedance sensor.

12. The impedance sensor of claim 11, wherein the first and second driver electrodes are in contact with the composite membrane sensor assembly.

13. The impedance sensor of claim 11, wherein the first and second driver electrodes are driven at multiple frequencies.

14. The impedance sensor of claim 11, wherein the first and second driver electrodes are driven with an alternating current signal.

15. The impedance sensor of claim 11, further comprising a programmable fluid processor coupled to the sensor electrode.

16. A method for determining a characteristic of a packet, comprising:

flowing a fluid containing a packet through an impedance sensor that includes first and second driver electrodes driven in counter phase to produce a net output signal of about zero at a sensor electrode;

measuring perturbations of the net output signal arising from changes in impedance associated with the presence of the packet within the impedance sensor; and

determining the characteristic of the packet from the perturbations.

17. The method of claim 16, wherein the characteristic of the packet comprises packet size.

18. The method of claim 16, wherein the characteristic of the packet comprises packet transit time through the impedance sensor.

19. The method of claim 16, wherein the characteristic of the packet comprises packet velocity.

20. The method of claim 16, wherein the characteristic of the packet comprises packet concentration.

21. The method of claim 16, wherein the characteristic of the packet comprises a relative displacement within the impedance sensor.

22. The method of claim 16, wherein the characteristic of the packet comprises packet impedance.

23. A method for determining a characteristic of a particle, comprising:

providing an impedance sensor comprising a sensor electrode, first and second driver electrodes coupled to the sensor electrode and driven in counter phase to produce a net output signal of about zero at the sensor electrode, and a channel defined through the sensor electrode and the first and second driver electrodes;

applying a multi-frequency drive signal to the first and second driver electrodes;

receiving an impedance signal from the sensor electrode;

determining in-phase and out-of-phase components of the impedance signal at the frequencies of the drive signal;

detecting changes in the in-phase and out-of-phase components indicative of a particle event; and

analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle.

24. The method of claim 23, wherein the drive signal comprises a composite of separate waveforms of different frequencies, each frequency being an integer multiple of a fundamental frequency.

25. The method of claim 24, wherein the drive signal consists of 8 separate sine waves having frequencies f, 2f 4f 8f, 16f, 32f 64f and 128f.

26. The method of claim 23, wherein impedance signal components are represented as 24 bit words.

27. The method of claim 23, further comprising deriving a composite signal comprising a moving sum of magnitudes of changes of the in-phase and out-of-phase components.

28. The method of claim 27, wherein detecting changes indicative of a particle event comprises determining when the composite signal exceeds a threshold value above a noise floor.

29. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises calculating an overlap integral.

30. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises constraining curves associated with the in-phase and out-of-phase components to obey a Kramers-Kronig relationship.

31. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a velocity of the particle.

32. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a mean fluid velocity.

33. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a concentration of particles.

34. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a size of the particle.

35. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a relative displacement of the particle.

36. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a dielectric property of the particle.

37. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a conductivity property of the particle.

38. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining an impedance of the particle.

39. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a cell membrane permittivity of the particle.

40. The method of claim 23, wherein analyzing portions of the impedance signal about the particle event to determine the characteristic of the particle comprises determining a cytoplasmic permittivity of the particle.