Droplet generation in co-flow microfluidic channels with vibration

We quantitatively characterize the perturbed droplet generation in co-flow microfluidics with mechanical vibration by estimating the fluctuations in the flow rate of inner fluid. We show the variation of generation frequency and uniformity of droplets as the frequency and amplitude of vibration. Synchronized droplet generation occurs in certain range of the vibration frequency that is predicted by our model. Besides, we scale the droplet size by incorporating the effects of vibration, inner and outer flows. The vibration is found to be capable of promoting the dripping, suppressing the jetting and even shifting the jetting into the dripping when the jet length is sufficiently short. The delayed dripping-jetting transition is characterized in a phase diagram by taking vibration into consideration. Our results unveil the mechanism of mechanically perturbed droplet generation and provide valuable guidelines for practical applications of vibration-enhanced droplet generation.