Differential Microstrip Sensor for Complex Permittivity Characterization of Organic Fluid Mixtures

Area of Science:

• Electrical Engineering
• Biomedical Sensing
• Materials Science

Background:

• Accurate characterization of complex permittivity is crucial for analyzing biological fluids like urine.
• Existing methods for urine analysis can be complex and time-consuming.
• Development of sensitive and cost-effective sensors is needed for point-of-care diagnostics.

Purpose of the Study:

• To design, fabricate, and test a highly sensitive microstrip differential sensor for complex permittivity characterization of urine samples.
• To evaluate the sensor's performance using both numerical simulations and experimental validation.
• To demonstrate the sensor's capability for analyzing urine-water mixtures with varying concentrations.

Main Methods:

• Designed a microstrip differential sensor with two pairs of open-stub resonators operating at 1.25 GHz.
• Fabricated the sensor on an affordable FR-4 Epoxy substrate (1.6 mm thickness).
• Utilized numerical simulations and experimental measurements with urine-water mixtures (0-100% urine) and nonlinear least square curve fitting in MATLAB.

Main Results:

• The sensor demonstrated high sensitivity for complex permittivity characterization of urine samples.
• Simulations covered 32 data groups with water content varying from 0% to 100%.
• Experimental validation used specific urine concentrations (0%, 20%, 33%, 50%, 66%, 100%), achieving a sensing sensitivity of approximately 3%.

Conclusions:

• The developed microstrip sensor is a viable tool for accurate complex permittivity characterization of urine.
• The sensor's design on FR-4 Epoxy substrate offers a cost-effective solution for urine analysis.
• This technology holds potential for non-invasive and rapid urine diagnostics.