Highly Sensitive Corrugated QMSIW Microfluidic Sensor for Biofuel Adulteration Detection

This paper introduces a microfluidic sensor that employs a corrugated quarter-substrate integrated waveguide (QMSIW) antenna for detecting biofuel adulteration. The selfdiplexing capability is achieved by incorporating a diagonal rectangular slot in the top metallic layer of the antenna. The sensor resonates at two distinct frequencies, 2.83 GHz and 3.24 GHz, while maintaining an isolation of more than 35 dB between the two antenna elements. Two microfluidic pockets made of PDMS are integrated onto the antenna, each dedicated to analyzing different biofuel adulteration scenarios. The interaction between the biofuels and the electromagnetic fields results in a shift in the resonant frequencies, enabling both simultaneous and individual detection of adulterants. A frequency shift of 500 MHz is observed for pure biofuel. The sensor achieves high sensitivities of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.5 \text{GHz} /$</tex> RIU and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.47 \text{GHz} /$</tex> RIU for detecting different adulterants in biofuels, making it a reliable solution for fuel quality monitoring and contamination detection.