Nanomechanical resonators are routinely used for identification of various analytes such as biological and chemical molecules, viruses, or bacteria cells from the frequency response. This identification based on the multimode frequency shift measurement is limited to the analyte of mass that is much lighter than the resonator mass. Hence, the analyte can be modeled as a point particle and, as such, its stiffness and nontrivial binding effects such as surface stress can be neglected. For heavy analytes (>MDa), this identification, however, leads to incorrectly estimated masses. Using a well-known frequency response of the nanomechanical resonator in air, we show that the heavy analyte can be identified without a need for highly challenging analysis of the analyte position, stiffness, and/or binding effects just by monitoring changes in the quality factor (Q-factor) of a single harmonic frequency. A theory with a detailed procedure of mass extraction from the Q-factor is developed. In air, the Q-factor depends on the analyte mass and known air damping, while the impact of the intrinsic dissipation is negligibly small. We find that the highest mass sensitivity (for considered resonator dimensions ∼zg) can be achieved for the rarely measured lateral mode, whereas the commonly detected flexural mode yields the lowest sensitivity. Validity of the proposed procedure is confirmed by extracting the mass of heavy analytes (>GDa) made of protein and Escherichia coli bacteria cells, and the ragweed pollen nanoparticle adsorbed on the surface of the nanomechanical resonator(s) in air, of which the required changes in the Q-factor were previously experimentally measured. Our results open a doorway for rapid detection of viruses and bacteria cells using standard nanomechanical mass sensors.

中文翻译：

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通过监测空气中纳米机械谐振器品质因数的变化，对重分析物和大型生物聚集体进行质谱分析。

纳米机械谐振器通常用于根据频率响应来识别各种分析物，例如生物和化学分子，病毒或细菌细胞。这种基于多模频移测量的识别仅限于质量比谐振器质量轻得多的分析物。因此，可以将分析物建模为点粒子，这样，可以忽略其刚度和诸如表面应力之类的重要结合作用。但是，对于重分析物（> MDa），这种识别会导致错误估计质量。利用空气中纳米机械共振器的众所周知的频率响应，我们表明无需对分析物的位置，硬度，单谐波频率的Q因子）。建立了一种从Q因子中提取质量的详细过程的理论。在空气中，Q因子取决于分析物的质量和已知的空气阻尼，而固有耗散的影响很小。我们发现，对于很少测量的横向模式，可以实现最高的质量灵敏度（对于所考虑的谐振器尺寸〜zg），而通常检测到的挠曲模式的灵敏度最低。通过提取由蛋白质和大肠杆菌制成的重分析物（> GDa）的质量，可以验证所提出方法的有效性。细菌细胞，以及豚草花粉纳米颗粒吸附在空气中的纳米机械共振器表面上，其中先前需要对Q因子进行必要的测量。我们的结果为使用标准的纳米机械质量传感器快速检测病毒和细菌细胞打开了大门。