Frequency-Switchable Microfluidic CSRR-Loaded QMSIW Band-Pass Filter Using a Liquid Metal Alloy

Area of Science:

• Electromagnetics
• Microwave Engineering
• Materials Science

Background:

• Substrate-integrated waveguide (SIW) filters are crucial components in microwave circuits.
• Achieving tunable or switchable filter characteristics is essential for advanced wireless systems.
• Complementary split-ring resonators (CSRRs) offer versatile electromagnetic response manipulation.

Purpose of the Study:

• To propose and demonstrate a frequency-switchable band-pass filter.
• To integrate microfluidic channels with liquid metal for dynamic frequency tuning.
• To investigate the performance of a complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) filter.

Main Methods:

• Design and fabrication of a CSRR-loaded QMSIW band-pass filter.
• Integration of microfluidic channels using polydimethylsiloxane (PDMS) and 3D-printed frames.
• Utilizing eutectic gallium-indium (EGaIn) liquid metal for frequency switching.
• Characterization of filter performance in both initial and loaded states.

Main Results:

• The filter exhibits two distinct states with tunable center frequencies (2.205 GHz and 2.56 GHz).
• Fractional bandwidth is switchable from 6.80% to 9.38% with minimal change in coupling coefficient.
• The liquid metal injection alters the CSRR shape and external quality factor, enabling frequency shift.
• Repeatable performance was confirmed after liquid metal removal.

Conclusions:

• The proposed CSRR-loaded QMSIW filter effectively demonstrates frequency-switchable operation.
• Microfluidic integration with liquid metal provides a viable method for dynamic filter tuning.
• The design shows potential for reconfigurable RF front-end applications.