Controllable Droplet Generators by Light-Heat Energy Conversion for Selective Particle Encapsulation

Water-in-oil droplet generation for object encapsulation is of increasing importance in biochemical reaction, drug diagnostics, and environmental science. Optofluidic technique is a powerful tool for manipulating mesoscopic particles and droplets within a continuous liquid phase. Here, we report a flexible and miniaturized droplet generator based on a microvortex chip by light-heat energy conversion to fuse, trap, and release picoliter aqueous droplets in the immiscible carrier oil. The droplet sizes in the generators can be tuned by the flow rate of the vortices. Further, it is demonstrated that the generated droplet can realize size-selective encapsulation of micro-matters with tunable rotating trajectories. The results showed that the microvortex-based droplet generator propose a method for the stable fusion and encapsulation of droplet with controllable positions and volumes. This system will provide a controllable microfluidic environment for droplet tweezers, micro-reactors, micro-mixers, and object encapsulation in practical applications.