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

Abstract

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 cm 2 /𝜇g and around 60, respectively. The results indicate the potential of a highly sensitive microfluidic sensor system for the applications in viscous media.

AlN-based film buck acoustic resonator operated in shear mode for detection of carcinoembryonic antigens

“…Simultaneously, the (101) orientation is co-existent corresponding with the c-axis tilted AlN, which enables the sensor excitation of the shear mode wave and is appropriate for the applications in liquid conditions. [14][15][16][17][18] The measured return loss (S 11 ) parameters of the fabricated FBAR-PDMS sensor in air and Tris-HCl buffer are shown in Fig. 4, where both the longitudinal and shear modes are obviously observed.…”

“…This result occurred due to the compression of the longitudinal mode acoustic wave in the liquid, which resulted in the attenuation of the energy as it propagated through the liquid. 14,15 While the shear mode acoustic wave propagates parallel to the lm's surface, conning the energy in the liquid. Thus the energy is reected back from the interface which ensures high performance of the resonator in liquid.…”

“…[7][8][9][10][11][12][13] However, FBAR is usually operated in a purely longitudinal thickness mode, which can cause a severe dissipation of the acoustic energy into the sample liquid resulting in a poor quality factor and a decrease of mass sensitivity. 14 On the other hand, in the FBAR the particle displacement of the shear mode acoustic wave is parallel to the lm surface. Consequently, compression is not produced in the liquid, so there is little energy leakage damping in the liquid.…”

“…Therefore, in liquid, the shear mode wave is more suitable than the longitudinal mode wave. [14][15][16][17][18] For a given FBAR conguration, the c-axis inclined piezoelectric lm is feasible for excitation of the shear mode wave, and the shear mode will result with inclinations of greater than 10 already. 19 When FBAR sensors are used as a biosensor, a common detection method is to drop the analyte on the active area of the FBAR, which affects the nal test results.…”

“…PDMS provides an alternative analyte sampling approach and demonstrates its remarkable advantages, including easy operation, low reagent consumption, lower time-consumption and easy transplantation. 14,20 The integrated FBAR and PDMS microuidic provides a compact system for the measurements in liquid environments.…”