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Review of Scientific Instruments / Volume 81 / Issue 7 / ARTICLES / General Instruments

Rev. Sci. Instrum. 81, 075108 (2010); http://dx.doi.org/10.1063/1.3462974 (10 pages)

Two-dimensional dielectric spectroscopy: Implementation and validation of a scanning open-ended coaxial probe

Mohammad Habibi1, David P. Klemer1, and Valerica Raicu2

1Department of Electrical Engineering, University of Wisconsin, Milwaukee, Wisconsin 53211, USA
2Department of Physics and Department of Biological Sciences, University of Wisconsin, Milwaukee, Wisconsin 53211, USA

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(Received 1 May 2010; accepted 17 June 2010; published online 23 July 2010)

Dielectric spectroscopy is a powerful tool for characterizing and classifying materials based on their electrical properties. In order to perform dielectric measurements on a sample with spatially varying properties, the measuring probe typically is repositioned manually on the surface of the sample for each measurement. In this paper, we present a novel technique, based on a reconfigurable multielectrode array, which facilitates the recording of measurements at various different spatial locations without physically moving the measuring electrodes. By electronically selecting one of the electrodes as the inner line and connecting the remainder of the electrodes together to form the outer line, an open-ended coaxial probe is created, which can be repositioned by simply selecting different electrode combinations; hence the name of a “traveling” coaxial probe. The geometric factor, or the cell constant, of each coaxial probe in the array was estimated from measurements on saline solutions with known electrical characteristics. In order to validate the setup for measurement of dielectric properties of biological cells, the plasma membrane capacitance and cytoplasm conductivity of yeast cells suspended in aqueous solutions were measured and compared to results from published reports. Dielectric spectroscopy imaging was carried out on tissue phantoms made of an agar gel with inclusions consisting of concentrated yeast cell suspensions. Measurements were performed on the phantoms, and the dielectric data were spatially mapped with respect to electrode location. The spatial electrical data correlated precisely with locations of yeast cell inclusions within the phantoms.

© 2010 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. METHODS
    1. Instrument design
    2. Electrode polarization
    3. Measurement protocols and data analysis
    4. Preparation of electrodes
    5. Preparation of samples
  3. RESULTS AND DISCUSSION
    1. Characterization of the electrodes
      1. Geometrical factor
      2. Penetration depth
      3. Environmental coupling
    2. Application to characterization of biological samples
      1. Analysis of yeast cell suspensions using a three-shell model
      2. Phantom measurements
    3. Comparison to electrical impedance tomography (EIT) techniques
  4. CONCLUSION

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KEYWORDS and PACS

Keywords

dielectric properties, probes

PACS

  • 77.22.-d

    Dielectric properties of solids and liquids

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.3462974

PUBLICATION DATA

ISSN

0034-6748 (print)  
1089-7623 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

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    References

    K. S. Cole and R. H. Cole, J. Chem. Phys. 9, 341 (1941)JCPSA6000009000004000341000001.

    H. P. Schwan and C. D. Ferris, Rev. Sci. Instrum. 39, 481 (1968)RSINAK000039000004000481000001.

    Y. Feldman, R. Nigmatullin, E. Polygalov, and J. Texter, Phys. Rev. E 58, 7561 (1998).


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