Newsletter  2023.11  Index

Theme : "Mechanical Engineering Congress, 2023 Japan (MECJ-23)" Preface Hideo MORI, Tetsuya KANAGAWA Why do mistakes communicate and spread? (Diffusion and prevention of misperceptions regarding fluid mechanics) Ryozo ISHIWATA (Kanagawa Institute of Technology) Toward Digital Twin Numerical Turbine Satoru YAMAMOTO (Tohoku University) Measurements of turbulent wall pressure fluctuation field in a turbulent boundary layer and the wing-flat plate juncture flow using the many-channel microphone array Yoshitsugu NAKA (Meiji University) PSP and TSP for measuring pressure and temperature fields on wall surfaces and their applications Yasuhiro EGAMI (Aichi Institute of Technology) Flow measurement using MEMS differential pressure sensor Hidetoshi TAKAHASHI (Keio University), Takuto Kishimoto (Keio University), Kei Ohara (Keio University), Kyota Shimada (Keio University) Flexible Sheet Sensor for Advanced Flow Monitoring Masahiro MOTOSUKE (Tokyo University of Science)

 

Flexible Sheet Sensor for Advanced Flow Monitoring

Abstract

Masahiro MOTOSUKE Tokyo University of Science

In this article, our recent researches on the development of flexible flow sensors for advanced flow monitoring are summarized. The need for flow measurement in narrow gaps or tiny spaces and on curved surfaces has been strongly required. Our group developed a thin, small, and flexible flow sensor based on microelectromechanical systems (MEMS) technology, which can simultaneously measure the flow velocity (or wall shear stress) at the sensor and flow direction. The principle of flow sensing relies on thermal measurement around a microheater embedded on the sensor surface (Fig. 1).

Here, we introduced two applications of this flexible flow sensor; one is the detection of three-dimensional flow separation and the other is perspiration monitoring. In both cases, microelectrode patterns are integrated with a thin polyimide film (Fig. 2). Before the actual fabrication of the sensor, numerical simulation was performed to optimize the geometry and structure of the sensor.

In the detection of flow separation, we developed a 1-mm circular heater with six temperature sensors around it. Flow velocity or wall shear stress can be determined from the energy consumption of the heater, and flow direction can be measured from surrounding temperature sensors (Fig. 3). A correlation curve for wall shear stress under different velocities from 30 to 150 m/s was obtained. Also, a correlation of flow direction with temperature sensor outputs was acquired with a 360º range. This multi-directional flow sensor successfully evaluated complicated three-dimensional flow separation in fluid machinery.

In perspiration monitoring, a microchannel made of flexible rubber to introduce sweat flow to the detection part is bonded on the sensor so that the sensor structure is flexible (Fig. 4). This sensor can be simply attached to human skin to continuously monitor the sweat rate of the human during exercise. A temperature compensation successfully works in different temperature environments. (Fig. 5)

Key words

Flexible flow sensor, Flow separation, Microelectromechanical systems (MEMS), Sweat rate

Figures

Fig. 1 Principle of MEMS-based thermal flow sensor.

Fig. 2 Developed flexible flow sensor.

Fig. 3 A picture of wind tunnel (top), relationship between heater output and wall shear stress (left), and relationship between three outputs from temperature sensor pairs and flow angle (right).

Fig. 4 Developed flexible sensor for perspiration monitoring.

Fig. 5 Performance of temperature compensation. Temperatures of reference sensor and microheater under different flow rate (left) and temperature difference (right).