A MEMS-based Air Flow Sensor with a Free-standing Micro-cantilever Structure.

Yu-Hsiang Wang,Che-Ming Chiang,Chia-Yen Lee

doi:10.3390/s7102389

Yu-Hsiang Wang, Che-Ming Chiang + Show 1 more

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https://doi.org/10.3390/s7102389

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Abstract

This paper presents a micro-scale air flow sensor based on a free-standingcantilever structure. In the fabrication process, MEMS techniques are used to deposit asilicon nitride layer on a silicon wafer. A platinum layer is deposited on the silicon nitridelayer to form a piezoresistor, and the resulting structure is then etched to create afreestanding micro-cantilever. When an air flow passes over the surface of the cantileverbeam, the beam deflects in the downward direction, resulting in a small variation in theresistance of the piezoelectric layer. The air flow velocity is determined by measuring thechange in resistance using an external LCR meter. The experimental results indicate that theflow sensor has a high sensitivity (0.0284 ω/ms-1), a high velocity measurement limit (45ms-1) and a rapid response time (0.53 s).

Highlights

Flow measurement is a necessary task in such diverse fields as medical instrumentation, process control, environmental monitoring, and so forth
Many previous studies have demonstrated the successful application of MEMS techniques to the fabrication of a variety of flow sensors capable of Sensors 2007, 7 detecting both the flow rate and the flow direction [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
While the fabrication of the flow sensor was straightforward, the maximum measurable flow rate was of the order of just 20 ms-1, and the practicality of the device for flow rate sensing applications characterized by flow rates as high as 40 ms-1 was severely limited

Summary

Introduction

Flow measurement is a necessary task in such diverse fields as medical instrumentation, process control, environmental monitoring, and so forth. Qiu et al [1] presented a micro gas-flow sensor featuring a heat sink and a flow guide on the underside of the sensing element, and showed that the device had a power consumption of 8 mW and was capable of measuring flow velocities of up to 5 ms-1. Neda et al [2] fabricated a single-wire-type thermal flow sensor incorporating a polysilicon micro-heater, and demonstrated that the device had a broad measurement range of 0.005-35 ms-1, a rapid response time of just 0.14 ms (90%), and a power consumption of 6 mW. An increasing number of non-thermal flow sensors have been developed Such devices have the advantages of a lower power consumption and an improved potential for integration with other sensors. While the fabrication of the flow sensor was straightforward, the maximum measurable flow rate was of the order of just 20 ms-1, and the practicality of the device for flow rate sensing applications characterized by flow rates as high as 40 ms-1 was severely limited

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Conclusion