Scanned impedance imaging system method and apparatus

• US 20070007975A1
• Filed: 07/11/2005
• Published: 01/11/2007
• Est. Priority Date: 07/11/2005
• Status: Active Grant

• Current Assignee: Brigham Young University (The Church of Jesus Christ of Latter-Day Saints)
• Original Assignee: Brigham Young University (The Church of Jesus Christ of Latter-Day Saints)
• Inventors: Schultz, Stephen, Hawkins, Aaron, Oliphant, Travis
• Granted Patent: US 7,205,782 B2
• Time in Patent Office: Days
• US Class Current: 324/724
• CPC Class Codes: G01R 27/26 Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables

Abstract

The resolution and contrast of impedance measurements and scans are improved by using a non-contact impedance probe comprising an inner conductor configured to bear a measurement signal and an outer conductor configured to bear a shielding signal. The measurement signal and shielding signal are selected to increase the directionality of the flux emitted from the impedance probe. In one embodiment, the measurement signal and the shielding signal are phase locked signals. A sample may be placed in a basin having a conductive surface that receives the flux emitted from the impedance probe. By filling the basin with a conductive solution, direct contact between the probe and the sample may be avoided along with the associated variability in contact resistance. The small highly-directional flux emitting area achievable with the present invention enables high resolution high contrast non-contact scanning of biological and non-biological materials.

Claims

1. A system for non-contact impedance measurement of a sample, the system comprising:

an impedance probe configured to provide electrical flux;

a basin configured to retain a conductive solution, the basin comprising a conductive surface configured to receive the electrical flux from the impedance probe;

a scanner configured to move the impedance probe in close proximity to a sample placed within the basin; and

wherein the impedance probe comprises inner and outer conductors, the outer conductor configured to shield the inner conductor, and wherein the inner and outer conductors bear signals selected to improve electrical flux directionality and measurement resolution.

2. The system of claim 1, wherein the inner conductor bears a measurement signal and wherein the outer conductor bears a shielding signal, and wherein the measurement and the shielding signals are phase locked.

3. The system of claim 2, further comprising a signal generator configured to provide a first input signal and a second input signal corresponding to the measurement signal and the shielding signal respectively.

4. The system of claim 1, wherein the outer conductor is coaxial to the inner conductor.

5. The system of claim 1, further comprising a height sensor configured to provide height information to the scanner.

6. The system of claim 1, wherein the scanner comprises a positioning actuator and position control module.

7. The system of claim 1, further comprising a response meter configured to measure a response of the impedance probe to an input signal.

8. The system of claim 1, further comprising a data logger configured to record impedance measurements.

9. The system of claim 1, wherein the conductive solution has a conductivity between 1000 ohm-cm and 20 Mohm-cm.

11. The method of claim 9, wherein the signals are phase locked.

12. The method of claim 9, further comprising measuring a probe position.

13. The method of claim 9, further comprising recording a plurality of impedance measurements.

14. The method of claim 9, further comprising advancing to a new position.

10. A method for non-contact impedance measurement of a sample, the method comprising:

providing an impedance probe configured to provide electrical flux;

providing a basin comprising a conductive surface configured to receive electrical flux from the impedance probe;

moving the impedance probe in close proximity to a sample submerged in a conductive solution within the basin; and

wherein the impedance probe comprises inner and outer conductors, the outer conductor configured to shield the inner conductor, and wherein the inner and outer conductors bear signals selected to improve electrical flux directionality and measurement resolution.

15. An apparatus for non-contact impedance measurement of a sample, the system comprising:

an impedance probe comprising an inner conductor, an insulator, and an outer conductor, the outer conductor configured to shield the inner conductor, the insulator configured to insulate the inner conductor from the outer conductor, and wherein the inner conductor, insulator, and outer conductor comprise materials suitable for immersion into an aqueous solution;

a reference impedance element connected in series to the inner conductor; and

a signal generator configured to provide a first input signal to the reference impedance element and a second input signal to the outer conductor, wherein the first and second input signals are selected to improve electrical flux directionality and measurement resolution.

16. The apparatus of claim 15, wherein the first and second input signals are phase locked.

17. The apparatus of claim 15, wherein the first and second input signals are the same signal.

18. The apparatus of claim 15, wherein the inner conductor has a diameter of less than 500 micrometers.

19. The apparatus of claim 18, wherein the insulator has a thickness that is greater than 0.1 times, and less than 10 times, the diameter of the inner conductor.

20. The apparatus of claim 18, wherein the outer conductor has a thickness that is greater than half the diameter of the inner conductor.

21. The apparatus of claim 15, wherein the inner conductor has a diameter of less than 500 micrometers.

22. The apparatus of claim 15, wherein a plurality of impedance probes are integrated onto a substrate.

23. The apparatus of claim 21, wherein a plurality of impedance probes have a common outer conductor.

24. The apparatus of claim 15, further comprising a spacer configured to maintain a substantially fixed distance between the inner conductor and a sample.