Dynamics of tandem bubble interaction in a microfluidic channel

The dynamics of tandem bubble interaction in a microfluidic channel (800 x 21 mu m, W x H) have been investigated using high-speed photography, with resultant fluid motion characterized by particle imaging velocimetry. A single or tandem bubble is produced reliably via laser absorption by micron-sized gold dots (6 mu m in diameter with 40 mu m in separation distance) coated on a glass surface of the microfluidic channel. Using two pulsed Nd:YAG lasers at lambda = 1064 nm and similar to 10 mu J/pulse, the dynamics of tandem bubble interaction (individual maximum bubble diameter of 50 mu m with a corresponding collapse time of 5.7 mu s) are examined at different phase delays. In close proximity (i.e., interbubble distance = 40 mu m or gamma = 0.8), the tandem bubbles interact strongly with each other, leading to asymmetric deformation of the bubble walls and jet formation, as well as the production of two pairs of vortices in the surrounding fluid rotating in opposite directions. The direction and speed of the jet (up to 95 m/s), as well as the orientation and strength of the vortices can be varied by adjusting the phase delay. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3626134]