Vibration-assisted preparation of core-shell capsules by millifluidics

• A vibration-assisted microfluidic system is developed for the controlled preparation of core-shell capsules. • The periodic vibration shifts the breakup dynamics from interfacial tension-dominated to vibration-dominated schemes. • Systematic investigations reveal a large operational range for the stable preparation of single-core capsules. • The capsules demonstrate tunable size, good monodispersity , high encapsulation efficiency and strong mechanical strength . • Probiotics-loaded capsules show a good storage stability and are capable of controlling the release of probiotics. Core-shell capsules are good carriers for various applications, such as food administration and drug delivery. The precise control of the emulsification process is essential for the controlled preparation of core–shell capsules. Here, a vibration-assisted millifluidic system is developed to achieve the controlled preparation of millimeter-size core–shell capsules with tunable size and property. With vibration, the breakups of the inner and middle phases are dominated by the large-amplitude vibration. The phase diagram of core–shell capsules with vibration shows a larger area of one-core capsules. The influences of experimental parameters on capsule properties are systematically investigated and analyzed. Probiotics-loaded core–shell capsules show a small size distribution, strong mechanical strength and good storage stability. Encapsulated probiotics could be released by crushing the shell or dissolving the shell in warm water. Therefore, the vibration-assisted millifluidic system provides a good platform for the stable preparation of biocompatible core–shell capsules for controlled release.