A Generic Signal Shielding Technique for MEMS Resonators in Conductive Liquid

The challenges of operating Micro-Electro-Mechanical Systems (MEMS) resonators in conductive liquid medium were addressed in this study, which is crucial for applications in biomedical sensing, chemical analysis, and environmental monitoring. High ionic conductivity has been encountered by traditional approaches, leading to substantial feedthrough interference that conceals resonant signals. We introduce a novel shielded signal pad/interconnect configuration to overcome these limitations. By driving/sensing the resonator through the shielded pad/interconnect and grounding the exposed ones, feedthrough effects were reduced, and resonance readability was enhanced across a much broader frequency spectrum compared to previous method. Improved performance of AlN-based MEMS resonators in liquid medium was demonstrated through experimental results, with phase noise performance in ionic environments of −22.17 dBc/Hz at 10 Hz offset and −99.45 dBc/Hz at 10 kHz offset. A mass resolution of 3.3 pg in ionic liquids is achieved by the resonator/oscillator, proving its applicability for real-time sensing. These findings offer a robust solution for maintaining MEMS resonator/oscillator functionality in conductive liquid and pave the way for future advancements.