High-Sensitivity Slot-Loaded Microstrip Patch Antenna for Sensing Microliter-Volume Liquid Chemicals with High...

Area of Science:

• Electromagnetics and Microwave Engineering
• Sensor Technology
• Materials Science

Background:

• Accurate measurement of liquid chemical properties is crucial in various scientific and industrial applications.
• Existing microwave sensors often face challenges with high-permittivity and high-loss tangent liquids.
• Microstrip patch antennas (MPAs) are versatile for sensing applications but require optimization for specific liquid analytes.

Purpose of the Study:

• To develop a high-sensitivity microwave sensor for measuring microliter volumes of liquid chemicals.
• To enhance the relative permittivity sensitivity of a microstrip patch antenna (MPA) using a novel slot design.
• To investigate the sensor's performance with liquids exhibiting high relative permittivity and high loss tangents.

Main Methods:

• A rectangular single-ring complementary split ring resonator (SR-CSRR) slot with a bottom-edge center split (BCS) was integrated into an MPA.
• The SR-CSRR-BCS slot-loaded MPA was designed and fabricated on an RF-35 substrate.
• A quarter-wavelength transformer was used to mitigate impedance mismatch for high loss tangent liquids.
• Resonant frequency shifts of the input reflection coefficient were measured using water, methanol, and ethanol.

Main Results:

• The SR-CSRR-BCS slot-loaded MPA demonstrated the highest sensitivity for relative permittivity changes (1-10) compared to other slot designs.
• The sensor achieved a measured sensitivity of 0.45% for water with 15 μL volume.
• The proposed sensor design outperformed existing antenna-based microwave sensors in terms of sensitivity.

Conclusions:

• The novel SR-CSRR-BCS slot-loaded MPA design significantly enhances sensitivity for measuring liquid chemicals.
• The sensor is effective for analyzing microliter volumes of liquids with high relative permittivity and high loss tangents.
• This work presents a promising advancement in microwave sensing technology for chemical analysis.