Microwave microfluidic sensors for analyzing magnetic bead-based bioliquids: from theory to experimental validation

Area of Science:

• Microwave Engineering
• Microfluidics
• Biosensing

Background:

• Microfluidic devices are crucial for precise liquid handling in biosensing.
• Microwave sensing offers non-invasive material characterization.
• Detecting magnetic beads in solutions requires sensitive and accurate methods.

Purpose of the Study:

• To introduce and validate two novel microwave sensors for magnetic bead solutions.
• To explore the use of coplanar waveguide (CPW) and defect ground structure (DGS) for sensing.
• To investigate the combined effects of permittivity and permeability on microwave sensor performance.

Main Methods:

• Fabrication and experimental validation of a wideband transmission line sensor (1-110 GHz).
• Development and testing of a resonant sensor (approx. 25 GHz) with a spiral DGS.
• Analysis of transmission parameters (|S11|, |S21|) using various solutions and magnetic beads.
• Utilizing terahertz (THz) spectroscopy to measure permittivity of magnetic bead solutions.

Main Results:

• The transmission line sensor effectively detects magnetic beads via |S11| variations across a broad frequency range.
• The resonant sensor shows a redshift in resonance frequency with increased real permeability and reduced quality factor with increased imaginary permeability.
• A decrease in |S21| was observed with increased real permeability, aiding signal detection.
• THz spectroscopy provided insights into the permittivity of magnetic bead solutions.

Conclusions:

• The developed microwave microfluidic sensors demonstrate high sensitivity for magnetic bead detection.
• Co-utilization of permittivity and permeability enhances detection sensitivity in biosensors.
• These sensors show potential for applications in cell sorting and precise bioliquid analysis.