Microbubble formations in MEMS-fabricated rectangular channels: A high-speed observation

Abstract A microfluidic device that consists of MEMS-fabricated rectangular channels is developed for stable and sequential production of monodispersed microbubbles. The central inlet for gas phase is located between two inlets for liquid phases, where the device works as a two-fluid atomizer. The interfacial flow mechanism of microbubble formation at the junction of the inlets in the device is investigated using a high-speed visualization technique and digital image processing. The periodic formation process is successfully realized by the consideration of the wettability between the microbubble and the channel wall. The produced microbubbles are relatively uniform in size, and the size is controlled from 113 to 153 μm by changing the flow rates of the liquid and gas phases. Furthermore, a simple theoretical model to predict the equivalent diameter of microbubbles is developed by considering the mass balance of the gas phase in the formation process, where the experimental and theoretical results are in reasonable agreement.

[1]  Chih-Ming Ho,et al.  Transport of bubbles in square microchannels , 2002 .

[2]  Mo Bai,et al.  Formation of bubbles in a simple co-flowing micro-channel , 2007 .

[3]  G. Whitesides,et al.  Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up. , 2006, Lab on a chip.

[4]  Brochard-Wyart,et al.  Dynamics of dewetting. , 1991, Physical review letters.

[5]  G. Whitesides,et al.  Nonlinear dynamics of a flow-focusing bubble generator: an inverted dripping faucet. , 2005, Physical review letters.

[6]  Paul A Dayton,et al.  On-chip generation of microbubbles as a practical technology for manufacturing contrast agents for ultrasonic imaging. , 2007, Lab on a chip.

[7]  H. Kotera,et al.  Development of Atomization Method in Microchannel and Its Basic Characteristics , 2005 .

[8]  S. Quake,et al.  Dynamic pattern formation in a vesicle-generating microfluidic device. , 2001, Physical review letters.

[9]  Mitsutoshi Nakajima,et al.  The generation of highly monodisperse droplets through the breakup of hydrodynamically focused microthread in a microfluidic device , 2004 .

[10]  Toshiro Higuchi,et al.  Droplet formation in a microchannel network. , 2002, Lab on a chip.

[11]  Satoyuki Kawano,et al.  Micro cell encapsulation and its hydrogel-beads production using microfluidic device , 2007 .

[12]  S. Kawano,et al.  Sequential Production of mm-Sized Spherical Shells in Liquid-Liquid Gas Systems , 1996 .

[13]  K. Suslick,et al.  Air-filled proteinaceous microbubbles: synthesis of an echo-contrast agent. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[14]  S. Kawano.  Molecular dynamics of rupture phenomena in a liquid thread , 1998 .

[15]  Toru Torii,et al.  Controlled production of monodisperse double emulsions by two-step droplet breakup in microfluidic devices. , 2004, Langmuir : the ACS journal of surfaces and colloids.

[16]  S. Quake,et al.  Microfluidics: Fluid physics at the nanoliter scale , 2005 .