On-chip encapsulation via chaotic mixing

A microfluidic device for production of uniform size capsules with a prescribed membrane thickness is described. It is versatile, novel and suitable for various polymerization reactions. Parameters such as polymerization time and reagent concentrations can be precisely tuned to control the membrane properties. The device features a part which allows to overcome the diffusion barrier by initiating interfacial polymerization via chaotic mixing. It also allows the termination of the reaction and the collection of the resulting capsules. We observe different typical dynamical phenomena occurring in capsules during their flow along the microchannel, namely wrinkling of the membrane, parachute and bullet shapes and bursting of the capsules due to strong hydrodynamical flow. In addition to production, the monitoring of capsule dynamics in flow gave a possibility to estimate the elastic surface modulus \(E_{{\rm S}}\) and the membrane thickness t. We found that \(E_{{\rm S}}\) can be as low as 6 × 10^?3 N m^?1 and that the thickness can be below 100 nm. This microfluidic device is therefore capable of producing uniform size capsule solutions with suitable membrane properties for the controlled release of drugs, and as a model system of red blood cells for microhydrodynamics experiments.