Experimental investigation of bubble formation in a microfluidic T-shaped junction

We have successfully fabricated a glass microfluidic device with a confined T-shaped junction in an ordinary laboratory without a clean room. In the microfluidic T-shaped junction, the bubble formation regime and the bubble volume generated were studied under different combinations of gas inlet pressure, liquid flow rate, liquid viscosity, and surface tension. It was found that both the minimum and the maximum gas inlet pressures for generating bubbles were larger than and proportional to the liquid pressure drop from the T-shaped junction to the channel outlet. The capillary number was found to have a significant influence on the bubble volume. An empirical relation is proposed to predict the bubble volume based on the capillary number and the liquid pressure drop from the T-shaped junction to the channel outlet.