Methodology for the Evaluation of Double Layered Microcapsule Formability Zone in Compound Nozzle Jetting Based on Growth Rate Ratio

Abstract

Doublelayered microcapsules, which usually consist of a core (polymeric) matrix surrounded by a (polymeric) shell, have been used in many industrial and scientific applications, such as microencapsulation of drugs and living cells. Concentric compound nozzlebased jetting has been favored due to its efficiency and precise control of the coreshell compound structure. Thus far, little is known about the underlying formation mechanism of doublelayered microcapsules in compound nozzle jetting. This study aims to understand the formability of doublelayered microcapsules in compound nozzle jetting by combining a theoretical analysis and numerical simulations. A linear temporal instability analysis is used to define the perturbation growth rates of stretching and squeezing modes and a growth ratio as a function of the wave number, and a computational fluid dynamics (CFD) method is implemented to model the microcapsule formation process in order to determine the good microcapsule forming range based on the growth ratio curve. Using a pseudobisection method, the lower and upper bounds of the good formability range have been determined for a given materialsnozzle system. The proposed formability prediction methodology has been implemented to model a waterpoly (lactidecoglycolide) (PLGA)air compound jetting system.