A simple, tunable, and highly sensitive radio-frequency sensor.

We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ∼20 MHz to ∼38 GHz. The effective quality factor (Qeff ) of the sensor is as high as ∼3.8 × 106 with 200 μl of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ∼1 GHz to ∼10 GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements.

[1]  A Monorchio,et al.  Waveguide Dielectric Permittivity Measurement Technique Based on Resonant FSS Filters , 2011, IEEE Microwave and Wireless Components Letters.

[2]  V. Molchanov,et al.  Frequency-tunable microwave dielectric resonator , 2001 .

[3]  Molly M. Stevens,et al.  Microwave Debye relaxation analysis of dissolved proteins: Towards free-solution biosensing , 2011 .

[4]  Michael D. Janezic,et al.  Quantitative Permittivity Measurements of Nanoliter Liquid Volumes in Microfluidic Channels to 40 GHz , 2010, IEEE Transactions on Instrumentation and Measurement.

[5]  Michael E. Tobar,et al.  Use of whispering-gallery modes for complex permittivity determinations of ultra-low-loss dielectric materials , 1999 .

[6]  D. A. Barrow,et al.  Novel Coupling Structure for the Resonant Coaxial Probe , 2012, IEEE Transactions on Microwave Theory and Techniques.

[7]  L. Katehi,et al.  High-$Q$ Tunable Microwave Cavity Resonators and Filters Using SOI-Based RF MEMS Tuners , 2010, Journal of Microelectromechanical Systems.

[8]  A. Kozhevnikov,et al.  Wideband radio-frequency device for measurements of dielectric properties of small volumes of liquids , 2010 .

[9]  Takaaki Sato,et al.  The cooperative dynamics of the H-bond system in 2-propanol/water mixtures: Steric hindrance effects of nonpolar head group , 2003 .

[10]  Alexander A. Barannik,et al.  High sensitivity microwave characterization of organic molecule solutions of nanoliter volume , 2009 .

[11]  T. J. Kippenberg,et al.  Ultra-high-Q toroid microcavity on a chip , 2003, Nature.

[12]  D. Dubuc,et al.  A Microwave and Microfluidic Planar Resonator for Efficient and Accurate Complex Permittivity Characterization of Aqueous Solutions , 2013, IEEE Transactions on Microwave Theory and Techniques.

[13]  Yang Yang,et al.  Distinguishing the viability of a single yeast cell with an ultra-sensitive radio frequency sensor. , 2010, Lab on a chip.

[14]  Takaaki Sato,et al.  Hydrophobic hydration and molecular association in methanol-water mixtures studied by microwave dielectric analysis , 2000 .

[15]  Shen-Iuan Liu,et al.  Microwave resonant absorption of viruses through dipolar coupling with confined acoustic vibrations , 2009 .

[16]  Chunrong Song,et al.  A radio frequency device for measurement of minute dielectric property changes in microfluidic channels , 2009 .