In microfluidic chip applications, the flow rate plays an important role. Here we propose a simple liquid flow rate sensor by using a tilted fiber Bragg grating (TFBG) as the sensing element. As the water flows in the vicinity of the TFBG along the fiber axis direction, the TFBG’s spectrum changes due to its contact with water. By comparing the time-swept spectra of the TFBG in water to that of the TFBG with water flowing over it, a spectral sweep comb was formed, and the flow rate can be detected by selecting a suitable sweeping frequency. The proposed sensor has a high $Q$-value of over 17,000 for the lower rate and a large detectable range from 0.0058 mm/s to 3.2 mm/s. And the calculated corresponding lower detectable flow rate of 0.03 nL/s is 3 orders magnitude better than that of the current fiber flowmeter. Meanwhile, the proposed sensor has the temperature self-compensation function for the variation of the external temperature. We believe that this simple configuration will open a research direction of the TFBG-deriving theory and configuration for lower flow rate measurements for microfluidic chip applications.

中文翻译：

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光谱扫梳液流量传感器

在微流控芯片应用中，流速起着重要作用。在这里，我们通过使用倾斜的光纤布拉格光栅（TFBG）作为传感元件，提出了一种简单的液体流速传感器。当水沿纤维轴方向在TFBG附近流动时，TFBG的光谱因与水接触而发生变化。通过将水中的TFBG的时间扫描光谱与流过水的TFBG的时间扫描光谱进行比较，形成了光谱扫描梳，可以通过选择合适的扫描频率来检测流速。建议的传感器具有很高的$问$-较低的速率值超过17,000，可检测范围从0.0058 mm / s至3.2 mm / s。所计算出的相应的较低可检测流速为0.03 nL / s，比当前的纤维流量计好3个数量级。同时，所提出的传感器具有针对外部温度变化的温度自补偿功能。我们相信，这种简单的配置将为TFBG衍生理论和配置的研究方向打开，以便为微流控芯片应用提供较低的流量测量。