Periodic generation and transport of micro air bubble in co-flowing of water in microchannels

The periodic generation of monodisperse micro air bubbles in water flowing in silicon microchannels having a trapezoidal cross section is investigated experimentally with the aid of high-speed CCD imaging technology. Air and water, used as the discontinuous and carrier fluid, are first co-flowing in the air microchannel and two adjacent water microchannels separately, and then converge in the main microchannel downstream. After breakup of the air bubble injected from the air microchannel, slug/bubbly flow regimes are formed periodically in the main microchannel. Correlations for the dimensionless bubble length and the dimensionless bubble formation frequency are obtained in terms of appropriate dimensionless parameters respectively.