Search

To quantitatively study the pressure fluctuations induced by the process of droplet formation in a T-junction microdroplet generator, the mathematical model which can accurately predict the amplitude and the frequency of the pressure fluctuations is demonstrated. Different geometries of the T-junction microchannels are designed for the experiments of droplet formation, and the time-varying pressure difference between the upstream and downstream of each droplet is measured during the droplet production progress. From both theoretical and experimental study, it can be observed the pressure difference is a periodic function of time for the whole process of droplet generation. In particular, the frequency of the pressure fluctuations coincides with the production rate of droplets, and the amplitude of the pressure fluctuations varies with the geometrical parameters of the T-junctions. Additionally, good agreements are shown between the theoretical calculations and the experimental measurements of the magnitude of the pressure fluctuations. Therefore, our mathematical model is validated experimentally, and the magnitude of the pressure fluctuations can be drastically reduced by optimization of the geometrical parameters of the T-junction. [ABSTRACT FROM AUTHOR]

To precisely control the size of monodisperse droplets for droplet microfluidics, we here establish a closed-loop control system with real-time feedback of droplet length during droplet generation. Particularly, the microvalves are integrated into the system to control the flow rates of the two immiscible fluids. From experimental measurements, we observe that the droplet length is a linear function of the flow-rate ratio for low capillary numbers ( C a ≤ 0.1). More importantly, the coefficients of the linear relation are determined by the geometry of the microchannel, and independent of the viscosity of the fluids. Based on MATLAB Simulink, the deviation between the predicted and measured droplet length is quantitatively studied. By using a PI controller, both the response speed and control accuracy of the droplet length can be greatly improved for the closed-loop control system. As a result, high monodispersity and uniformity of droplet generation can be achieved in a T-junction microdroplet generator. [ABSTRACT FROM AUTHOR]