文摘
This paper presents a study of bubble dynamics in a resonator-shaped microfluidic chamber, including the bubble generation, radial oscillation and translation. The microfluidic chamber is incorporated with a piezoelectric actuator as part of the chamber wall, and DI-water is pumped throughout the chamber. Our experiments show that under the actuation at 1 kHz, the bubbles are generated, starting near the center of the chamber, growing up in size and even moving upstream against the main flow. Such type of bubble generation is different from those conventional bubble generations in microchannels by introducing external gas or laser radiation, and the bubble dynamics presented in this study is different from existing studies focusing on high-frequency actuations. To interpret our experimental findings, both numerical simulations and analytical modeling are conducted for studying the bubble dynamics in the low-frequency actuation case. The results show that the bubble generation and oscillations are due to the high-amplitude pressure fluctuations inside the chamber, corresponding to the actuations. Specifically, under the low-frequency actuation, the primary Bjerknes force becomes insignificant and the bubble translation against the main flow is attributed to the chamber sidewall attracting effect on the bubbles.