Acoustic aligning and trapping of microbubbles in an enclosed PDMS microfluidic device

Manipulation of microbubbles has become an increasingly important technique for numerous lab-on-a-chip bioengineering researches and applications, such as the microbubble based molecular imaging and targeted drug delivery. In this paper, a microfluidic device consisting of an enclosed polydimethylsiloxane (PDMS) microcavity integrated with a surface acoustic wave (SAW) generator is developed to align and trap the microbubbles. The microbubbles are lined up to multiple parallel lines by a standing SAW (SSAW) generated by the reflection at the PDMS boundary. Moreover, the microbubbles may be trapped at the center of the microcavity by the acoustic streaming generated by the bulk compressional wave in the confined fluid due to the mode-conversion originated from SAW. The trapping rate increases with increasing input power or decreasing fluid flow rate. With the advantages of low power consumption, miniaturization, rapid and simple fabrication, this micro device could potentially be a useful tool in some biomedical applications.