Acoustic radiation-free surface phononic crystal resonator for in-liquid low-noise gravimetric detection

Abstract

Acoustic wave resonators are promising candidates for gravimetric biosensing. However, they generally suffer from strong acoustic radiation in liquid, which limits their quality factor and increases their frequency noise. This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal (SPC) consisting of periodic high aspect ratio electrodes to address the above issue. The acoustic wave generated in the SPC is slower than the sound wave in water, hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface. This energy confinement results in a significant quality factor improvement and reduces frequency noise. The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process. Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency. The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators. Thus, this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.

Phononic Crystal Sensors: A New Class of Resonant Sensors—Chances and Challenges for the Determination of Liquid Properties

“…Anchor losses no more dominate the Q (Ardito et al, 2016). Very recently, Gao et al (2021) have exploited the surface phononic crystal (SPC) concept for SPC resonators operating in a liquid (Gao et al, 2021). They show the velocity of Rayleigh waves in the proposed sensor can be reduced to a value lower than the sound velocity in water, thereby suppressing the propagation of acoustic waves and hence eliminating acoustic radiation.…”

Shear Horizontal Phononic Metasurface for In-Liquid Gravimetric Biosensing

“…The acoustic wave produced in the PM has a velocity lower than the sound velocity in water, which _______ cannot propagate in water and thus eliminates the acoustic radiation. The previously reported vertically polarized PM (VP-PM) resonator derived from the classical Rayleigh waves demonstrated the radiation suppression phenomenon 7 . However, the vertical polarization together with the processinduced defects in the HARE compromised the suppression effect, leading to a limited Q factor improvement.…”

“…Nevertheless, the shear polarization cannot prevent the energy leakage through acoustic radiation. To address this problem, phononic metasurface (PM) is introduced 7,8 .…”

A High-Sensitivity Gravimetric Biosensor Based on S1 Mode Lamb Wave Resonator

“…Recently, a potential method was proposed to suppress acoustic radiation and improve the mass sensitivity in water at high frequencies. This idea was exploited in biosensors based on Lamb wave resonators (LWRs) [ 18 , 19 , 20 , 21 ]. Similarly to other acoustic wave resonators, the application of Lamb wave resonators in mass sensing mainly depends on the frequency shift of the device.…”