There is an indispensable need for fluid flow rate and direction sensors in various medical, industrial and environmental applications. Besides the critical demands on sensing range of flow parameters (such as rate, velocity, direction and temperature), the properties of different target gases or liquids to be sensed pose challenges to the development of reliable, inexpensive and low powered sensors. This paper presents an overview of the work done on design and development of Microelectromechanical system (MEMS)-based flow sensors in recent years. In spite of using some similar principles, diverse production methods, analysis strategies, and different sensing materials, MEMS flow sensors can be broadly categorized into three main types, namely thermal sensors, piezoresistive sensors and piezoelectric sensors. Additionally, some key challenges and future prospects for the use of the MEMS flow sensors are discussed briefly.

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Design and applications of MEMS flow sensors: A review

Coriolis mass flowmeter (CMF) is a kind of flow measurement instrument, which can directly measure the high-precision transient mass flow parameters. Also, the vibration characteristic of the U-shaped measuring tube inside is one of the important factors that determine the measuring accuracy. The pulsating flow through the measuring tube will lead to the motion component except for the main vibration frequency, which will affect the phase difference calculation and reduce the measurement accuracy of the mass flowmeter. This article presents a method to improve the accuracy of U-tube CMF based on variable step-size least-mean-square (LMS) filter and Hilbert transform with interval shifting under pulsating flow. Experimental work was conducted on a dynamic experimental platform of pulsating flow. Experimental results show that the stability and accuracy of the proposed algorithm are better than that of the traditional CMF phase difference calibration method. The mean time difference error is $9.0525~\mu \text{s}$ , and the mean time difference relative error is 5.806%. The calibration effect is more than 88.0934% better than other traditional algorithms. It is verified that it has a good error calibration effect for pulsating flow at various frequencies.

Error Analysis and Accuracy Calibration Method of U-Tube Coriolis Mass Flowmeter Under Pulsating Flow

On nonlinear stability of fluid-conveying imperfect micropipes

https://northumbria-test.eprints-hosting.org/id/document/270123

Viscoelastically coupled mechanics of fluid-conveying microtubes

As the first endeavour, the influence of a pulsatile flow on the large-amplitude bifurcation behaviour of viscoelastic microtubes subject to longitudinal pretention is studied with special consideration to chaos. The viscoelastic microtube is surrounded by a nonlinear spring bed. A modified size-dependent nonlinear tube model is developed based on a combination of the couple stress theory and the Euler–Bernoulli theory. Hamilton’s principle, as an equation derivation technique, and Galerkin’s procedure, as a discretisation technique, are used. Finally, the discretised differential equations of the pulsatile fluid-conveying viscoelastic microscale tube are solved using a time-integration approach. It is investigated that how the bifurcation response for both motions along the axial and transverse axes is highly dependent of the mean value and the amplitude of the speed of the pulsatile flow.

/pdf/chaotic-oscillations-of-viscoelastic-microtubes-conveying-2h4u2iovsn.pdf

Chaotic oscillations of viscoelastic microtubes conveying pulsatile fluid

This work presents the modelling, design, fabrication and test of the first micro Coriolis mass flow sensor fully fabricated in SU-8 by photolithography processes The sensor consists of a channel with rectangular cross-section with inner opening of 100 μm × 100 μm and is actuated at resonance by Lorentz forces Metal tracks for the actuation current are deposited on top of the chip The chip has been tested over a flow range of 0–800 mg/min in the case of water and 0–650 mg/min for isopropyl alcohol (IPA) to confirm that the sensor measures true mass flow (at the maximum flow of the tested range, 0–800 μl/min for both water and IPA, it results in a pressure drop of 098 bar for water and 197 bar for IPA)

Su-8 micro coriolis mass flow sensor

The cross-sectional shape of microchannels is, dependent on the fabrication method, never perfectly circular. Consequently, the channels deform with the pressure, which is a non-ideal effect in flow sensors, but may be used for pressure sensing. Multiple suspended channels with different lengths were modeled, fabricated, and characterized to verify the use and the scalability of this effect for pressure sensing. Furthermore, it is shown that the pressure dependence can be distinguished from the Coriolis effect in microfabricated Coriolis mass flow sensors, enabling the measurement of the pressure next to flow and density with only the flow sensor itself. In addition, this allows for further improvement in the accuracy of the flow measurement by correcting for the small pressure dependence.

Integrated pressure sensing using capacitive Coriolis mass flow sensors

Coriolis mass flow sensors mechanically detect mass flows using a vibrating channel. For microfabricated sensors, thermomechanical noise causes random vibrations and defines therefore a fundamental limit to the resolution of the sensor. This is modeled using the equipartition theorem. In an experimental setup, the displacement of the channel due to thermomechanical noise is measured using a laser Doppler vibrometer for temperatures between approximately 300 K and 700 K. The results show RMS vibration amplitudes of 38 pm to 57 pm for a bandwidth of 13 Hz, as predicted by the model. This corresponds to a noise equivalent mass flow of 0.3 ng s−1. It is shown that the resolution of the currently most sensitive Coriolis mass sensor is still one to two orders of magnitude above the thermal noise limit.

Experimental analysis of thermomechanical noise in micro Coriolis mass flow sensors

https://ris.utwente.nl/ws/files/6777143/alveringh_mee_original.pdf

Improved capacitive detection method for Coriolis mass flow sensors enabling range/sensitivity tuning

This paper reports on a fluid viscosity sensor consisting of pressure sensors fully integrated with a Coriolis mass flow sensor. The sensor is capable of measuring viscosities of both liquids and gases through a mathematical model. For liquids, this model is simply the Hagen-Poiseuille equation. For gases, a more elaborate model is derived, taking into account compressibility and additional pressure losses due to channel geometry. Viscosities of (mixtures of) water and isopropanol were measured and correspond well with values found in literature. Viscosities of nitrogen and argon were measured with accuracies of −0–12%, depending on input pressure and mass flow rate. Improvement of the mathematical model could lead to higher accuracy and less dependence on mass flow or pressure.

Dennis Alveringh

Papers

Su-8 micro coriolis mass flow sensor

Integrated pressure sensing using capacitive Coriolis mass flow sensors

Experimental analysis of thermomechanical noise in micro Coriolis mass flow sensors

Improved capacitive detection method for Coriolis mass flow sensors enabling range/sensitivity tuning

Fully integrated mass flow, pressure, density and viscosity sensor for both liquids and gases