Fabrication and Evaluation of a Flexible MEMS-Based Microthermal Flow Sensor.

Myoung-Ock Cho,Woojin Jang,Si-Hyung Lim

doi:10.3390/s21238153

Abstract

Based on the results of computational fluid dynamics simulations, this study designed and fabricated a flexible thermal-type micro flow sensor comprising one microheater and two thermistors using a micro-electromechanical system (MEMS) process on a flexible polyimide film. The thermistors were connected to a Wheatstone bridge circuit, and the resistance difference between the thermistors resulting from the generation of a flow was converted into an output voltage signal using LabVIEW software. A mini tube flow test was conducted to demonstrate the sensor’s detection of fluid velocity in gas and liquid flows. A good correlation was found between the experimental results and the simulation data. However, the results for the gas and liquid flows differed in that for gas, the output voltage increased with the fluid’s velocity and decreased against the liquid’s flow velocity. This study’s MEMS-based flexible microthermal flow sensor achieved a resolution of 1.1 cm/s in a liquid flow and 0.64 cm/s in a gas flow, respectively, within a fluid flow velocity range of 0–40 cm/s. The sensor is suitable for many applications; however, with some adaptations to its electrical packaging, it will be particularly suitable for detecting biosignals in healthcare applications, including measuring respiration and body fluids.

Highlights

We developed a flexible microthermal flow sensor for simultaneously measuring high flow rates in gases and liquids from tens to hundreds of milliliters/minute using the micro-electromechanical system (MEMS) process on a flexible substrate
The simulation visualized the temperature difference between the the two thermistors, and the variations provided the magnitude of the output voltage, two thermistors, and the variations provided the magnitude of the output voltage, which which is directly or inversely proportional to the flow velocity depending on the properties is directly or inversely proportional to the flow velocity depending on the properties of of the fluid
According to the computational fluid dynamics (CFD) analysis for the temperature difference between the therthermistors of the sensor electrodes with respect to the flow rate of the fluid, in the case of mistors of the sensor electrodes with respect to the flow rate of the fluid, in the case of gas, gas, ∆T (ThermistorDownstream − ThermistorUpstream ) showed a tendency to increase as the

Summary

Introduction

The use of micro-electromechanical system (MEMS) technology satisfies various demands in the field of microsensors for small size, low power consumption, low cost, mass production, high accuracy, high sensitivity, etc. These advantages have led to multiple advances in the field of micro flow sensors [1]. MEMS-based micro flow sensors are found in various applications in industrial settings. In the field of micro flow sensors, the most notable recent developments have been related to the healthcare sector and the measurement of biosignals, and many studies and advancements are currently underway in this area [4,5,6]

Methods

Results

Conclusion