Title: US20050032233A1: Resonance-enhanced dielectric sensing of chemical and biological species
Derwent Title: Dielectric sensing method for detecting and classifying chemical and biological materials (e.g. soil contaminants), involves detecting resonance patterns and identifying a shift in resonance frequency and change of line width [Derwent Record]
Country: US United States of America
Inventor: Gopalsami, Nachappa; Naperville, IL, United States of America
Raptis, Apostolos C.; Downers Grove, IL, United States of America
Assignee: THE UNIVERSITY OF CHICAGO
other patents from UNIVERSITY OF CHICAGO (599445) (approx. 271)
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Published / Filed: 2005-02-10 / 2003-08-08
Application Number: US2003000637127
IPC Code: Advanced: G01N 22/00;
Core: more...
IPC-7: G01N 27/00;
ECLA Code: G01N22/00;
U.S. Class: 436/149; 422/082.01;
Government Interest: CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant to Contract No. W-31-109-ENG-38 between the United States Government and Argonne National Laboratory.
Priority Number:
2003-08-08 US2003000637127
Abstract: A dielectric sensing method and apparatus are provided for detection and classification of chemical and biological materials. Resonance patterns of a sample within a resonator are detected for identifying a shift in resonance frequency and a change of line width before and after introduction of the sample. The identified shift in resonance frequency and change of line width are used for determining a complex dielectric constant of the sample for the material detection and classification. A degree of selectivity at any excitation frequency is enabled for the dielectric sensing method from the manner in which the complex dielectric constant of a material affects the resonance pattern of the resonator with respect to shift in resonance frequency and the change in line width. By selecting the excitation frequencies to generally correspond to one of the resonance frequencies of the sample material under test, the degree of selectivity and the sensitivity of detection are enhanced.
SUMMARY OF THE INVENTION
In brief, a dielectric sensing method and apparatus are provided for detection and classification of chemical and biological materials. Resonance patterns of a sample within a resonator are detected for identifying a shift in resonance frequency and a change of line width before and after introduction of the sample. The resonance patterns can be generated either as a function of sample concentration or as a function of excitation frequency for a given sample. The identified shift in resonance frequency and change of line width are used for determining a complex dielectric constant of the sample for the material detection and classification.
In accordance with features of the invention, a degree of selectivity at any excitation frequency is enabled for the dielectric sensing method of the invention from the manner in which the complex dielectric constant of a material affects the resonance pattern of the resonator with respect to shift in resonance frequency and the change in line width. By selecting the excitation frequencies to generally correspond to one of the resonance frequencies of the sample material under test, the degree of selectivity and the sensitivity of detection are enhanced.
In accordance with features of the invention, a cylindrical microwave cavity resonator is used for dielectric sensing and changes in the resonant frequency and quality factor before and after introduction of the sample for small perturbation to the cavity field are identified. The cylindrical microwave cavity resonator is used for gas and solid samples and an RF parallel-plate resonator is used for subsurface liquid contaminant detection.
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