Analysis of Tandem Bubble Interaction and Jet Formation in a Microfluidic Channel

Abstract

Tandem bubble interactions have been shown to produce jets that can be used to create membrane poration on single cells, and jet speed has been implicated as a critical parameter for tandem bubble-induced bioeffects. In this thesis, the dynamics of single and tandem bubbles in a microfluidic channel (25 × 800 μm in height and width) are investigated to access the effects of bubble size on tandem bubble interaction and resultant jet. Experimentally, the dynamics of bubble oscillation produced by laser irradiation of a gold dot (15 nm thick and 6 μm in diameter) coated on the glass substrate of the microfluidic channel are captured by a high-speed camera, from which the time history of bubble size and jet speed are determined. Numerically, the bubble dynamics are simulated using 3DynaFS-BEM (DYNAFLOW, INC.) based on a potential flow model solved by boundary element method (BEM). By adjusting the initial conditions in the BEM code, the dynamics of laser-generated single bubbles of different sizes were matched with experimental results. The model was subsequently used to simulate the tandem bubble interactions in anti-phase oscillation. The results show that jet shape and volume are predominately controlled by the maximum diameter of the first bubble (D1) while jet speed is linearly correlated with the maximum diameter of the second bubble (D2). In comparison, jet momentum and kinetic energy are more sensitive to variations in bubble size and increase more rapidly with both D1 and D2, especially at large bubble sizes.