Electrostatic repulsion-based graphene multi-cavity array resonators for molecular-level detection

Resonant sensors offer high stability and sensitivity. Conventional silicon-based resonant sensors focused on micro sizes and kHz-level resonant frequencies ( f re ). Graphene, a two-dimensional material with remarkable electromechanical response efficiency, allows for the fabrication of resonators with MHz-level resonant frequencies, exhibits exceptional sensitivity to gases. The current single-cavity structure suffers from limitations such as low-quality factors, small sensitive area, and structural defects. This paper introduces a graphene multi-cavity array resonant (GMCAR) structure and a driving detection scheme based on electrostatic repulsion. The sensor achieves a fundamental f re of 126.16 MHz and a quality factor (Q) up to 135 at ambient temperature and pressure. Moreover, this sensor successfully detects nitrogen dioxide (NO 2 ) gas. The f re decreases approximately by 0.4 kHz, indicating the detection of NO 2 gas at a molecular level, with an estimated mass of 0.6 fg. The second vibration mode of the sensor is also detected and used for gas sensing.