Research Papers

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

[+] Author and Article Information
Yong Huang

e-mail: yongh@clemson.edu
Department of Mechanical Engineering,
Clemson University,
Clemson, SC 29634

Roger Markwald

Department of Regenerative Medicine
and Cell Biology,
Medical University of South Carolina,
Charleston, SC 29425

1Corresponding author.

Manuscript received May 31, 2012; final manuscript received January 4, 2013; published online April 8, 2013. Assoc. Editor: Ye Zhou.

J. Fluids Eng 135(5), 051203 (Apr 08, 2013) (8 pages) Paper No: FE-12-1271; doi: 10.1115/1.4023646 History: Received May 31, 2012; Revised January 04, 2013

Double-layered 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 nozzle-based jetting has been favored due to its efficiency and precise control of the core-shell compound structure. Thus far, little is known about the underlying formation mechanism of double-layered microcapsules in compound nozzle jetting. This study aims to understand the formability of double-layered 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 materials-nozzle system. The proposed formability prediction methodology has been implemented to model a water-poly (lactide-co-glycolide) (PLGA)-air compound jetting system.

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Fig. 1

Schematic of the compound nozzle and a compound jet

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Fig. 2

Schematic of the stretching and squeezing modes with inner and outer interfaces illustrated

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Fig. 5

Representative simulation results of compound jetting (a) case 1 (50 kHz) and (b) case 2 (60 kHz) (the microcapsule structure might be best viewed in a colored display)

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Fig. 3

The growth rate ratio with respect to the wave number

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Fig. 4

Computational domains setup

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Fig. 6

Growth rate as a function of wave number and some representative simulation results (radius ratio a = 1.87, density ratio b = 0.87, interfacial tension ratio γ = 1.08, and viscosity ratio m = 1.38 as specified in Table 1)

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Fig. 7

Growth rate ratio as a function of wave number and some simulation results using the same material properties and nozzle geometry as for Fig. 6




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