Scalable single-step microfluidic production of single-core double emulsions with ultra-thin shells

We report a versatile and robust device for the continuous production of double emulsion drops with very thin shell thicknesses, of about 5% of the radius: for emulsions 50 μm in radius the shells can be as thin as a few micrometers. Importantly, the viscosity of the oil shell can be varied from that of water up to 70 times that of water without compromising device operation. Furthermore, this device can be easily scaled-up as it is made through soft lithography; this may enable the production of industrial quantities of double emulsion drops with ultra-thin shells, which may serve as templates to form capsules with homogeneous shell thicknesses, useful beyond scientific applications.