Flexible on-chip droplet generation, switching and splitting via controllable hydrodynamics

Flexible droplet preparation and manipulation are significant for lots applications such as immunoreaction and monocellular culture. Herein, we present a novel method for effective on-chip droplet generation, splitting and switching via controllable hydrodynamics. The microchannel of the designed chip has 6 inlets and 3 three outlets. The water solution is injected from a specific inlet (inlet d), and the other 5 inlets are used to inject oil fluids. Under the shearing effect of immiscible oils, the water phase breaks into dispersed droplets first, and the generated droplets can be further split into daughter drops or switched into side outlets from the middle outlet. To investigate the hydrodynamic droplet manipulation behaviors, a two-dimensional simulation model based on phase-field method is established. Utilizing the computational model, we systematically analyze the influences of the flow rates of continuous and dispersed fluids and the manipulation modes on droplet generation, splitting and switching. The numerical results indicate that the droplets can be generated with controlled sizes. For instance, at Q(d) = 5 mu L/min and Q(c1), 2 = 5 mu L/min, the droplet diameter decreases from 89.2 mu m to 49.2 mu m as Q(s1,2) gradually rises from 15 mu L/min to 40 4/min. Moreover, the prepared droplets can realize on-demand splitting and switching. When Q(d), Q(c1,2), and Q(s1,2 )are fixed at 5 mu L/min, 5 mu L/min and 25 mu L/min, respectively, the generated droplet is split into different proportional daughter drops with the rising of Q(s3) (or Q(s4)) at first, and finally it is switched into the side-outlets when Q(s3) (or Q(s4)) is higher than 80 mu L/min. Therefore, this proposed droplet manipulation approach will be promising for various applications, and the numerical simulations can provide useful guidelines on the design and operation of droplet-based microfluidic systems.

Automated summary

This paper presents a method for effective on-chip droplet generation, splitting, and switching using controllable hydrodynamics. A two-dimensional simulation model based on the phase-field method is established to analyze the hydrodynamic droplet manipulation behaviors. The numerical results show that the droplets can be generated with controlled sizes and can realize on-demand splitting and switching.