Study on Flow Visualization in Microfluidics Fields

Research Project

Project/Area Number	13650240
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Thermal engineering
Research Institution	IBARAKI NATIONAL COLLEGE OF TECHNOLOGY
Principal Investigator	SHIBATA Yuichi Ibaraki National College of Technology, Mechanical Engineering Department, Associate Professor, 機械工学科, 助教授 (70178911)
Co-Investigator(Kenkyū-buntansha)	OSIKUBO Takeshi Ibaraki National College of Technology, Mechanical Engineering Department, Professor, 機械工学科, 教授 (80123983)
Project Period (FY)	2001 – 2002
Project Status	Completed (Fiscal Year 2002)
Budget Amount *help	¥2,900,000 (Direct Cost: ¥2,900,000) Fiscal Year 2002: ¥1,600,000 (Direct Cost: ¥1,600,000) Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
Keywords	Microfluidics / Microchannel / Visualization / Flow patterns / Gas-liquid two-phase / Bubble generation / T-junction / Capillary wave / 流れの可視化 / キャピラリー / 混合 / 気泡の浮力 / スラグ流 / 混合実験
Research Abstract	The field of microfluidics is developing rapidly with advances in MEMS (micro electro mechanical system) and μTAS (micro total analysis system) technologies. In various devices, controlling the flow rate of liquid or gas accurately at micro or nanoliter volume levels is required. In this work, the gas-liquid two-phase flow patterns in a microchannel T-junction have been examined. The two-phase flow patterns were observed in the T-junction under two different gas and liquid injection conditions. The flow patterns of liquid and gas in the microchannel after the T-junction were also observed and classified into three types depending on the flow rate, and a two-phase flow pattern map was constructed. The mechanism of bubble breakup at a micro T-junction has been experimentally and analytically investigated. Two-phase flow experiments have been performed using air and water in two different micro T-junction with cross sections of 100μm wide and 1mm height, and 100μm wide and 100μm height. In the T-junction with a 100μm wide and 1mm high cross section channel, the two-phase flow patterns could be classified into three types depending on the gas and liquid flow rates. A bubble was torn off from an air layer at the T-junction but the breaking point was not stable showing irregular fluctuations ; however, the basic mechanism of bubble generation due to breakage of an air layer was similar for the three flow patterns. For the micro T-junction with a 100μm wide and 100μm high channel cross section, the mechanism of air breakup was found to be due to an interaction between surface tension and pressure forces. A comparison of experimental results and a linear stability analysis showed good agreement, indicating the role of a capillary wave instability in causing the bubble generation at the T-junction.