A simple microfluidic device for fabrication of double emulsion droplets and polymer microcapsules

We demonstrate that by using a syringe needle, plastic tubing, two glass capillaries and epoxy glue a microfluidic device can be fabricated straightforwardly that allows for the production of double emulsions, or in other words the generation of droplets-in-droplets. The device in essence is a serial combination of droplet generation by co-flow and a T-junction. To reduce potential issues with channel wetting, we established that an "obstructed'' T-junction outperformed a conventional T-junction. We illustrate the versatility of our device through production of a range of polymer microcapsules, including ones that contain a waterborne dispersion of colour changing pigment, and microcapsules with compartmentalized ferrofluidic segments, that is capsules that contain more than one droplet of ferrofluid.