Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

R&D strategy for functional capsules

The flow-induced synthesis of non-spherical gel beads and microcapsules succeeds, when these particles are orientated and stretched due to the action of velocity gradients and are chemically fixed at the same time by polymerisation reactions. The simultaneous superposition of flow, gelation and relaxation leads to the formation of unusual shapes, such as rod-like particles, pearl strings or parachute shaped particles.

The synthesis of these capsules can be performed in a double capillary apparatus. In this instrument, the inner capillary is filled with an aqueous solution of calcium lactate and the outer tube contains a dilute solution of sodium alginate. As soon as these two liquids get in contact, a surface gelation occurs and a stable gel phase forms within a few milliseconds. The double capillary generates two concentric droplets, and the inner phase, containing the calcium ions, always remains in a liquid state.

The outer droplet finally forms the elastic biopolymer shell (skin). The inner phase can also contain additive chemical compounds like dyes or vitamins, unless it does not weaken the mechanical stability of the surrounding shell. The double capillary is inserted in a larger tube, where sunflower oil is flowing. As soon as the concentric droplets are formed at the tip of the double capillary, they are suspended to shear forces, which lead to large deformations. Due to the action of flow different types of non-spherical capsules and gel beads were synthesised.

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Universität - Gesamthochschule Essen
Universitaetstr. 3-5
45141 Essen
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