Fabrication of Double-Layered Alginate Capsules Using Coaxial Nozzle

Abstract

Multilayered encapsulation has been of great interest for various pharmaceutical, chemical, and food industries. Fabrication of well-defined capsules with more than one shell layer still poses a significant fabrication challenge. This study aims to investigate the feasibility of using a coaxial nozzle to fabricate double-layered (core–shell–shell) capsules during vibration-assisted dripping. A three-layered coaxial nozzle has been designed, manufactured, and tested for double-layered capsule fabrication when using sodium alginate solutions as the model liquid material for inner and outer shell layers and calcium chloride solution as the core fluid. To facilitate the droplet formation process, a vibrator has been integrated into the fabrication system to provide necessary perturbation for effective breakup of the fluid flow. It is demonstrated that double-layered alginate capsules can be successfully fabricated using the proposed three-layered coaxial nozzle fabrication system. During fabrication, increasing the core flow rate leads to an increase in capsule and core diameters while the inner and outer shell layer thicknesses decrease. Increasing annular flow rate results in an increase in capsule diameter and inner shell layer thickness while the outer shell layer thickness decreases. An increase in the sheath flow rate leads to an increase in capsule diameter and outer shell layer thickness but has no significant effect on the core diameter and inner shell layer thickness.

A novel semi-flexible coaxial nozzle based on fluid dynamics effects and its self-centering performance study

“…Ibrahim T Ozbolat et al 24 used stainless steel fixtures made by fine milling to align the two tubes to ensure their coaxiality; Buu Minh Tran 4 made triple-flow microfluidic devices through mold; Qing Gao 28 used porous clasps to ensure the coaxiality of coaxial nozzles; Alessandri 39 and S. Cem Millik 40 utilized a digital light processing 3D printer to fabricate microfluidic coaxial nozzles. Jin et al 41 manufactured a three-layer stainless steel nozzle, assembled through bolts, and fine-tuned the alignment of the three channels coaxially under a microscope. Jiaxing Gong et al 42 used epoxy resin to concentrically fix the inner and outer needles to ensure the coaxiality of the nozzle.…”

3D coaxial bioprinting: process mechanisms, bioinks and applications

“…Along the same lines, Attalla et al have showcased the fabrication of concentric human umbilical vein endothelial cell (HUVEC) and mouse 3T3 fibroblast laden tri-layered hollow fibers to mimic the compartmentalization in native blood vessels [21] similar to the work of Silva et al on the in-silico and in-vitro assessment of coaxial nozzles for the fabrication of perfusable constructs with dimensions similar to that of human arteries [22]. Reproduced with permission from [20]. Copyright © 2021 The American Society of Mechanical Engineers.…”

“…This process enables for a simple single-step generation of tissue constructs. Jin et al have also shown that a double layered capsule can be formed wherein the extruded structure is arranged in core-shell-shell morphology for a potential application in controlled drug release [20]. Along the same lines, Attalla et al have showcased the fabrication of concentric human umbilical vein endothelial cell (HUVEC) and mouse 3T3 fibroblast laden tri-layered hollow fibers to mimic the compartmentalization in native blood vessels [21] similar to the work of Silva et al on the in-silico and in-vitro assessment of coaxial nozzles for the fabrication of perfusable constructs with dimensions similar to that of human arteries [22].…”

“…© IOP Publishing Ltd. CC BY 3.0. (c) A triple nozzle coaxial setup for fabrication of dual-shell constructs enabling better mimicry of native blood vessels.Reproduced with permission from[20]. Copyright © 2021 The American Society of Mechanical Engineers.…”

Advances in Coaxial Additive Manufacturing and Applications

“…Jin et al. [ 39 ] studied the feasibility of coaxial fabrication of doubled‐layer (core–shell–shell) capsules in a vibration‐assisted dripping process. The authors designed a three‐layered coaxial nozzle and carried a simulation, using ANSYS, of the fluid velocity distribution within the annular and the sheath channel of the nozzle in order to optimize the design before manufacturing the device.…”