Microfluidic chemical sensor based on SIW cavity

This paper presents a substrate-integrated-waveguide (SIW) cavity resonator with an introduction of a microfluidic channel to achieve a non-contact sensor for chemical sensing applications. The dominant mode resonant frequency of the cavity resonator is switched by injecting a very small amount of liquid (chemical) into microfluidic channel, which further results in a change in the effective dielectric constant. Initially, the two layers of SIW resonator are constructed, and then the microfluidic channel is etched on Polydimethylsiloxane (PDMS) material stuck between the two SIW layers for non-contact chemical sensing applications. S-parameters of the proposed SIW resonator are simulated and measured. The dominant mode frequency of the proposed structure is successfully switched from 18.46 GHz to 14.83 GHz when ethanol is injected and the frequency becomes 14.11 GHz when DI-water is injected into the microfluidic channel. The capability of the SIW cavity resonator to function as a chemical sensor is successfully demonstrated.