An approach for gas flow velocity measurement at two different closely located points using a simple device incorporating only one thermal sensing element, is introduced and the feasibility to determine different velocities is experimentally demonstrated. An electrostatically actuated initially curved bistable microbeam heated by an electric current and convectively cooled by airflow is switched between two stable locations through the snap-through (ST) and snap-back (SB) buckling mechanisms. The velocities of an air flow at these positions are obtained by measuring the critical ST and SB values of the actuation voltage. In the experiments, our $500~\mu \text{m}$ long, $2~\mu \text{m}$ wide single-crystal Si beam with $\approx \, 2.5\,\mu \text{m}$ nominal initial elevation demonstrated sensitivity of $S_{\text {ST}} \approx 0.25$ V/(m/s) and $S_{\text {SB}} \approx 0.84$ V/(m/s) at the ST and SB points, respectively. In the present device, the distance between the two measurement points is $\approx 10~\mu \text{m}$ . Our experimental results indicate that the suggested approach can be used for the velocity gradient measurements. The sensing principle relying on a single bistable sensing element opens new opportunities for measurement of gas flow velocity and velocity gradients at scales significantly smaller than the state-of-the-art multi hot-wire sensors.

中文翻译：

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使用单个弯曲双稳态微束进行流速梯度传感

介绍了一种使用仅包含一个热传感元件的简单设备在两个不同的靠近位置测量气体流速的方法，并通过实验证明了确定不同速度的可行性。由电流加热并由气流对流冷却的静电驱动的初始弯曲双稳态微束通过快速通过 (ST) 和快速回退 (SB) 屈曲机制在两个稳定位置之间切换。这些位置的气流速度是通过测量致动电压的临界 ST 和 SB 值获得的。在实验中，我们的 $500~\mu \text{m}$ 长， $2~\mu \text{m}$ 宽单晶硅光束 $\approx \, 2.5\,\mu \text{m}$ 标称初始高程显示灵敏度 $S_{\text {ST}} \约 0.25$ V/(m/s) 和 $S_{\text {SB}} \大约 0.84$ 分别在 ST 和 SB 点的 V/(m/s)。在本装置中，两个测量点之间的距离为 $\approx 10~\mu \text{m}$ . 我们的实验结果表明所建议的方法可用于速度梯度测量。依赖于单个双稳态传感元件的传感原理为以比最先进的多热线传感器小得多的尺度测量气体流速和速度梯度开辟了新的机会。