Enabling direct dense encapsulation of water-insoluble powder in hydrogel microcapsules by bubble-assisted encapsulation method

Encapsulating powder ingredients into hydrogel with programmable release ability is highly demanded in many fields including food engineering, medical and healthcare fields. However, directly adding water-insoluble powders into pre-gel solution makes the mixture susceptible to clogging problems during processing, thus limiting the loading rate. To address this problem, a new way to encapsulate water-insoluble powder ingredients without addition of any organic solvent named bubble-assisted encapsulation method is developed in this study. The powders were firstly encapsulated in hydrogel bubbles and further dispersed by T-shaped microfluidic flow to form the core/shell-structured powder in hydrogel microcapsules (P/H microcapsules). The obtained P/H microcapsules had an exceptionally high loading rate of water-insoluble powders up to 94.76%. The P/H microcapsules were freeze-dried for long-term storage, and meanwhile, the as-prepared microcapsules were able to swell rapidly to soft state before use. Moreover, with the well-defined core–shell structure, the P/H microcapsules were endowed with dual release capabilities to external stimuli. The bubble-assisted encapsulation method that enables direct dense encapsulation of powder ingredients at a high loading rate appears promising for water-insoluble food or pharmaceutical ingredients delivery.