A new droplets millifluidic/inverse gelation based process was used to produce core-shell alginate milli-capsules. Water-in-oil (W/O) emulsion dispersed phase containing Ca²⁺ ions was directly injected into a continuous alginate phase to generate a secondary W/O/W emulsion. Due to the cross-linking of alginate molecules by Ca²⁺ ions release, core-shell milli-capsules were formed with a very high oil loading. The influence of the curing time and of the storage conditions on capsules physico-chemical properties were investigated. It was first found as expected that alginate membrane thickness increased with curing time in the collecting bath. However, a plateau was reached for the higher curing times, in close relation with previous observations (Martins, Poncelet, Marquis, Davy, & Renard, 2017b) that an external oil layer surrounded the surface of W/O emulsion drops that acted as a barrier and hindered the release of aqueous CaCl₂ droplets during curing time. Compression experiments on individual capsules revealed that alginate membrane thickness was inversely related to its mechanical properties, i.e. the thicker membrane, the lower surface Young modulus. Surface Young modulus ranged from 61 to 26 N/m at curing times of 3 and 45 min, respectively. This result was explained in terms of enhanced swelling properties of alginate membrane with curing time or storage conditions. Drying capsules led to much more resistant membranes due to the loss of water. Oil loading of 80 wt% was obtained for dry capsules whatever the conditions used.

中文翻译：

---

核壳藻酸盐胶囊的表征

基于微滴/逆凝胶化的新液滴工艺用于生产核-壳藻酸盐毫胶囊。将包含Ca ²⁺离子的油包水（W / O）乳液分散相直接注入连续藻酸盐相中，以生成二次W / O / W乳液。由于藻酸盐分子被Ca ²⁺交联离子释放后，形成的核壳毫胶囊具有很高的油载量。研究了固化时间和贮存条件对胶囊理化性质的影响。首次发现，藻酸盐膜的厚度随收集槽中固化时间的增加而增加。然而，与以前的观察结果（Martins，Poncelet，Marquis，Davy和Renard，2017b）密切相关的是，更长的固化时间达到了平稳状态，即外部油层包围了W / O乳剂液滴的表面，起到了屏障并阻止CaCl ₂水溶液的释放固化过程中出现水滴。对单个胶囊的压缩实验表明，藻酸盐膜的厚度与其机械性能成反比，即膜的厚度更大，表面的杨氏模量更低。在3和45分钟的固化时间下，表面杨氏模量分别为61至26 N / m。用藻酸盐膜随着固化时间或储存条件增强的溶胀性能来解释该结果。由于水分的流失，干燥胶囊导致了更坚固的膜。无论使用何种条件，干胶囊的载油量均为80 wt％。