Particle-stabilized gel-core microcapsules: Synthesis and properties

•Processing of particle-stabilized gel-core microcapsules of 3–300μm diameter.•Capsules are mechanically stable and can be harvested as a dry powder.•Particle's microstructure is discussed as a function of gel-former concentration.•The swelling behavior of the capsules is described.•We discuss the release of dye as a function of particle size and capsule properties. We propose a new and versatile synthesis route for the formation of particle-stabilized gel-core microcapsules. With this route, microcapsules can be produced in a large size range of a few to hundreds of micrometres. Due to the high mechanical stability developed upon gelation, the capsules can be harvested as dry powders. Implementing in-situ hydrophobization to modify the wetting properties of particles allows preparing capsule shells from almost any kind of particulate materials. In the present work, we demonstrate the formation of microcapsules with shells from 60nm gamma alumina and 200nm alpha alumina particles. These particle shells are combined with sodium acrylate and poly(ethylene glycol) based gel-cores. Shape, gel-core microstructure, and swelling of the capsules in deionized water are characterized. Modelling the release of a low molecular weight dye from the capsules reveals Fickian kinetics for 16 and polymer relaxation dominated kinetics for 280μm sized capsules, respectively. Given the flexibility in materials selection, our processing route could lead to the design of new microcapsule systems for sensing and release applications.