Suspended microfluidic resonators enable detection of fluid density and viscosity with high sensitivity. Here, a two-legged suspended microchannel resonator that probes pico-litres of liquid is presented. The higher resonant modes (flexural and torsional) were explored for increased sensitivity and resolution. Unlike other reported microchannel resonators, this device showed an increase in the quality factor with resonant frequency value. The performance of the resonator was tested by filling the channel with three liquids, one at a time, over a density range of 779 - 1110 Kg/m^3 and a viscosity range of 0.89 - 16.2 mPa.s. The highest resolution obtained was 0.011% change in density. Measurements with torsional mode showed an improvement of about six times in sensitivity and about fifteen times in resolution compared to the first flexural mode. When the empty channel was filled with liquids of different viscosity, the quality factor of the first flexural mode remained overall constant with a variation below 3.3% between the fluids, and confirming the inherent property of suspended microchannel resonators. However, it significantly decreased for second flexural and torsional modes. No noticeable difference was observed in the quality factor between different liquid viscosities for all modes.

中文翻译：

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用于液体密度测量的悬浮微流体谐振器中的第二弯曲和扭转振动模式

悬浮式微流体谐振器能够以高灵敏度检测流体密度和粘度。在这里，提出了一种探测皮升液体的双腿悬浮微通道谐振器。探索更高的共振模式（弯曲和扭转）以提高灵敏度和分辨率。与其他报道的微通道谐振器不同，该器件的品质因数随谐振频率值而增加。谐振器的性能通过在 779 - 1110 Kg/m^3 的密度范围和 0.89 - 16.2 mPa.s 的粘度范围内填充三种液体（一次一种）来测试谐振器的性能。获得的最高分辨率是密度变化 0.011%。与第一种弯曲模式相比，扭转模式的测量显示灵敏度提高了约 6 倍，分辨率提高了约 15 倍。当空通道充满不同粘度的液体时，第一弯曲模式的品质因数保持总体恒定，流体之间的变化低于 3.3%，这证实了悬浮微通道谐振器的固有特性。然而，对于第二弯曲和扭转模式，它显着降低。对于所有模式，不同液体粘度之间的品质因数没有观察到明显差异。