Virtualization of fluid-dynamics in micro-air assisted extruders for food microfluidic based encapsulation

Microfluidic technique represents an interesting technological solution for the production of alginate microbeads in pharmaceutical, food and cosmetics industry. Given the characteristic small size of microfluidic devices and the extremely complex dynamics which are at the base of transport phenomena involved in this process, a purely experimental approach is not able to provide all significant data to design cheap but trustable devices. In this work, a virtual approach based on computational fluid dynamics analysis has been proposed to analyze the behavior of a micro air-assisted extruder and to provide mechanistic insight into the particle formation dynamics. The particle formation was characterized by a complex periodic dynamics, during which elongations and instabilities brought to merging of liquid droplets, of different main size, into bigger drops. Jet instabilities dominating the drops break-up dynamics were greatly influenced by geometric parameters: the fluid-dynamic analysis showed that small misalignment can dramatically change the jet breakup dynamics, introducing a completely different framework. The analysis proposed in this work represents a powerful tool for the design of simple and cheap microfluidic devices, capable of mass production of small (around 300 mu m of diameter) and regular alginate microbeads, at least for matrix encapsulation. (C) 2017 Elsevier Ltd. All rights reserved.