Microfluidic HMSIW based Self-Diplexing Antenna for Simultaneous Sensing of Liquid Samples

A microfluidic sensor based on a half-mode substrate integrated waveguide (HMSIW) is presented in this paper. For the first time, the simultaneous sensing is proposed utilizing the self-diplexing characteristics of the SIW antenna. Diplexing is achieved by loading a modified T-shaped slot on the top metallic plane of the SIW. The antenna resonates at 4.66 GHz and 4.81 GHz, with a minimum port isolation of $\gt30 {\mathrm {dB}}$. Two microfluidic pockets made up of PDMS are introduced on the diplexer antenna where the electric fields are maximum. For demonstration of simultaneous sensing, one of the fluidic pockets is filled with distilled water, and other is filled with ethanol. The interaction between the liquid materials and the electromagnetic fields provide the shift in the resonant frequency of the diplexer antenna. The self-dipleixng microfluidic sensor achieved a high sensitivity of 57.45 MHz/RIU and 89.76 MHz/RIU for distilled water and ethanol, respectively.