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.

声波谐振器是重力生物传感的有希望的候选者。然而，它们通常会在液体中受到强烈的声辐射，这限制了它们的品质因数并增加了它们的频率噪声。本文提出了一种基于局部谐振表面声子晶体（SPC）的无声辐射重力生物传感器，该传感器由周期性高纵横比电极组成，以解决上述问题。 SPC 中产生的声波比水中的声波慢，因此它可以防止声波在流体中传播，并导致能量限制在电极表面附近。这种能量限制可显着提高品质因数并降低频率噪声。所提出的 SPC 谐振器通过有限元分析进行数值研究，并通过基于电镀的制造工艺进行实验实现。实验结果表明，在相似的工作频率下，SPC 谐振器的液体品质因数比传统瑞利波谐振器高 15 倍。所提出的使用SPC的辐射抑制方法也可以应用于其他类型的声波谐振器。因此，该方法可以作为提高许多声学生物传感器的液体品质因数和传感性能的通用技术。