Synthesizing microcapsules with controlled geometrical and mechanical properties with microfluidic double emulsion technology.

Using lithography-based microfluidic technology, we produce monodisperse single-core microcapsules with UV-cured TPGDA (triprophylene glycol diacrylate) shells. We show that the geometrical and mechanical characteristics of the microcapsules can be predicted on a quantitative basis and tuned by varying the flow conditions. Shell thicknesses are varied by changing the flow rates of the inner or intermediate phases, according to mass conservation constraint. Off-centering of the core with respect to the shell is controlled by varying the shell phase viscosity. The mechanical properties of the capsules can be varied by changing the flow conditions and are quantitatively predicted by a numerical simulation. The simulation moreover provides a correct qualitative description of their rupture. As a whole, the work carried out in the present paper shows, on a quantitative basis, that microfluidic technology allows to finely control the geometrical and mechanical properties of microcapsules generated on chip. The level of control we reach here is not accessible, by far, to conventional technologies. Combined with parallelization, the present work opens routes toward the production of novel families of monodisperse microcapsules with tunable properties.