The generation of water-in-water droplets have recently received great attention because of their highly biocompatible nature, but the controllable formation of such droplets is still challenging based on conventional flow-focusing microfluidic approaches. Serval alternative microfluidic techniques have been introduced with either active perturbation or passive formation. The first approach requires external components to perturb the flow, such as a piezoelectric disc to oscillate channel walls, a vibration table to oscillate the flow, or a peristaltic pressure pump to pulsate the fluid pressure. These approaches enable high throughput formation of water-in-water droplets but necessitate additional perturbation modules. The second approach simplifies the formation system by eliminating the external component requirement but suffers from droplet size-selectivity and throughput.<br/><br/>Here, we introduce a simple modification to the passive system of water-in-water droplets. The modification involves the integration of a microneedle into the conventional flow-focusing geometry. The integrated microneedle induces 3D flow focusing of the dispersed phase fluid, which significantly improves the formation of water-in-water droplets. With the microneedle-assisted microfluidic scheme, we are able to generate water-in-water droplets in a high throughput manner with great control over their size, ranging from 5 to 65 um.

High throughput creation of water-in-water droplets in a microfluidic flow-focusing device

2019 Fall National Meeting

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