柔性MEMS流速传感器的制造及其电路设计

Fabrication and Circuits Design of Flexible MEMS Flow Sensor

摘要:

针对流速传感器大多存在测量量程小、柔性小而无法适应较大量程和复杂曲面的测量问题, 提出了一种宽量程柔性MEMS流速传感器, 结合热损失和热温差的工作原理实现对流速的测量。选取聚酰亚胺(PI)作为柔性衬底材料和铂(Pt)薄膜为热敏材料, 采用金属牺牲层MEMS工艺制造了带空腔的柔性流速传感器芯片, 尺寸为9 mm×7 mm×30 μm。设计了采用双惠斯通电桥的恒温差测控电路。测量结果表明: 制造的柔性MEMS流速传感器的TCR为0.2418%/℃, 实验实现了0~36 m/s的输入风速测量, 在低速、高速段内的灵敏度分别为2和0.295 mV/(m/s)。同时, 测量电路还展现出良好的温度补偿效应。所提出的柔性MEMS流速传感器具有宽量程、测试精度高、灵敏度高和易于实施温度补偿的优点, 有望用于航空航天、国防等领域。

Abstract:

Nowadays, most of the flow sensors have the disadvantages of small measuring range and poor flexibility, thus they are unable to adapt to larger scale and complex surface measurements. This paper proposed a type of flexible MEMS flow sensor with wide measuring range, which was based on the combination of working principles of thermal loss and thermal temperature difference. Polyimide (PI) was selected as the substrate material and platinum (Pt) thin film was used as the thermal sensing elements. The flexible MEMS flow sensor chip with the size of 9 mm×7 mm×30 μm was fabricated employing MEMS process based on metal sacrificial layer. The constant temperature difference measurement and control circuit based on double Wheatstone bridge was designed. The testing results show that the temperature coefficient of resistance (TCR) of the fabricated flow sensor was 0.2418%/℃, the input air speed measurement in the range of 0~36 m/s was realized, and the sensitivity in high-speed and low-speed ranges were 2 mV/(m/s) and 0.295 mV/(m/s) respectively. In addition, The designed circuits demonstrated excellent effect of temperature compensation for accurate measuring results. The proposed flow sensor has the features of wide measuring range, high accuracy, high sensitivity and easiness to implement temperature compensation, and is expected to be applied to the aerospace, national defense and other fields.