Sensing Characteristics of Shear-Mode AlN Solidly Mounted Resonators with a Silicone Microfluidic System in Viscous Media

AlN solidly mounted resonators with silicone microfluidic systems vibrating in shear mode are fabricated and characterized. The fabrication process is compatible with integrated circuits and the c-axis tilted AlN films are deposited, which allow in-liquid operation through excitation of the shear mode. The silicone microfluidic system is mounted on top of the sensor chip to transport the analyses and confine the flow to the active area. The properties of sensor operation in air, deionized water, ethanol, isopropanol, 80% glycol aqueous solution, glycol, and olive oil are characterized. The effects of different viscosities on the resonance frequency shift and Q-factor of the sensor have been discussed. The sensitivity and Q value in glycol of the sensor are 1.52 MHz cm²/μg and around 60, respectively. The results indicate the potential of a highly sensitive microfluidic sensor system for the applications in viscous media.