Dynamics of tandem bubble interaction in a microfluidic channel.

Abstract

The dynamics of tandem bubble interaction in a microfluidic channel (800 × 25 μm2, W × H) are investigated using high-speed photography with resultant fluid motion characterized by particle imaging velocimetry. Single or tandem bubble is produced reliably via laser absorption by micron-sized gold dots (6 μm in diameter with 40 μm in separation distance) coated on a glass surface of the microfluidic channel. Using two pulsed Nd:YAG lasers at λ = 1064 nm and about 10 μJ/pulse, the dynamics of tandem bubble interaction (individual maximum bubble diameter of 50 μm with a corresponding collapse time of 5.7 μs) are examined at different phase delays. In close proximity (γ = 0.8), the tandem bubble interacts 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.