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A planar-type coaxial probe applicable to wide temperature and frequency range has been developed. The probe employs a dielectric with a low coefficient of thermal expansion to minimize the effect of thermal deformation for broad temperature measurements. Additionally, a detailed design methodology has been developed to optimize the probe apertures in an effort to minimize the measurement uncertainty while maximizing the operating bandwidth. For this purpose, thorough sensitivity analysis has been employed to correlate the probe structures and dimensions to the individual sensitivity parameters. The analysis has been validated by parametric experiments. By using the dielectric with a low coefficient of thermal expansion and optimizing the probe dimensions, accurate permittivity measurements have been demonstrated from -30 [degrees]C to 75 [degrees]C with 40-GHz bandwidth. With the application of the error-correction method, the measurement temperature range has been further extended all the way up to the boiling temperature of water (~ 100 [degrees]C). Furthermore, the complex permittivities of methanol have been measured from -30 [degrees]C to 50 [degrees]C and the dispersion parameters and full interpolation formulas have been extracted. Index Terms--Coaxial aperture, complex permittivity, planar-type probe, thermal deformation, wide temperature.

We developed a small-sized micromachined probe for the measurement of biological properties using microelectromechanical systems (MEMS) technology. We also experimentally showed the suitability of the micromachined probe for biological applications through in vivo, as well as in vitro measurements of various types of tissue. We measured the permittivities of 0.9% saline and the muscle and fat of pork using the micromachined probe after liquid calibration. The measured permittivities of 0.9 % saline and pork agreed well with both the expected values of the Cole-Cole equation along with the measured values obtained through the use of a 1-mm-diameter open-ended coaxial probe. We also performed in vivo measurements of breast cancer tissue implanted in an athymic nude mouse to show the suitability of the small-sized micromachined probe for practical biological applications. Through the obtained data, the capability of the micromachined probe of distinguishing different tissue types from one another was shown. The actual aperture size of the micromachined probe is only 240 [micro]m x 70 [micro]m and, therefore, we can extract the biological information from very small biological tissues and drastically decrease the invasiveness of this method through the implementation of the small probe created through the use of MEMS technology. Index Terms--In vitro, in vivo, microelectromechanical systems (MEMS), micromachined probe, permittivity measurement.