Using design of experiments to understand and predict polymer microcapsule core‐shell architecture

Abstract

Microbubbles (MBs) have tremendous application in a number of fields and strategies to impart them with tunable properties are of great interest to the scientific community. We recently reported a robust platform to produce polymeric MBs (more appropriately termed polymeric microcapsules, PMCs) with highly tunable materials properties by controlling the self-emulsification of oilin-water emulsions. In this study, we used design of experiments to develop a model to predict PMC internal architectures and mean particle diameter as a function of three key processing parameters: concentration of self-emulsifier (0.1% < F68 < 0.25% wt/wt), homogenization speed (1500-3000 rpm), and dilution factor (15 < DF < 30). We show that the homogenization speed and F68 concentration strongly influence both PMC morphology and size, with porous shell hollow cored PMCs being favored at low speeds and high F68 concentrations and nonporous-shelled gas-in-oil cored PMCs (g/o-PMCs) being favored at faster speeds and lower F68 concentrations. Models were subsequently validated by successfully predicting the relative percent yield and mean particle diameter of g-PMCs and g/o-PMCs for four sets of randomly selected factor settings. We anticipate that the results shown here will serve as a roadmap for other investigators interested in evaluating the utility of g-PMCs, g/o-PMCs or, combinations of the two, as novel gas carriers, diagnostic imaging agents, acoustic insulators, shock absorbers, and lightweight building materials, among many others. K E Y W O R D S bioengineering, colloids, manufacturing, surfaces and interfaces 1 | INTRODUCTION Microbubbles (MBs) are gas-filled particles with diameters ranging from a few micrometers to tens of microns. 1 The composition of the bubble shell (e.g., polymers, nanoparticles, and lipids) and the filling gas (air, oxygen, perfluorocarbons, and sulfur hexafluoride) are easily manipulated allowing one to alter important design parameters, such as stability, buoyancy, crush strength, thermal conductivity, and acoustic properties, among many others. 2-4 Intelligent design of the shell materials also permits one to engineer specific MB responses to external stimuli (e.g., to expand in response to increased temperature or ultrasound). 5 Because of this inherent tunablity, MBs continue to be evaluated for their potential use in a number of diverse industrial and medical

Assembly of Metal–Phenolic Networks onto Microbubbles for One‐Step Generation of Functional Microcapsules

“…Despite Zhang et al proposing the one-step microfluidic synthesis of polyelectrolyte microcapsules by combining an aqueous two-phase system and interfacial complexation in water/water/water double emulsion droplets, the oil-free microfluidic approaches are plagued by limited material options and low production rates. [7,8] Moreover, the manufacture of microfluidic devices contains additional manufacturing costs and complex surface treatment. [9] Thus, developing a simple and versatile method that enables the one-step generation of biocompatible microcapsules in large quantities under non-organic solvent conditions is still challenged.…”

Design of Experiment for Optimizing Microencapsulation by the Solvent Evaporation Technique

“…DoE is used to systematically address cause and effect relations between the parameters in study and experimental outputs, enabling to build a model to mathematically predict an output [ 17 , 21 , 22 , 23 , 24 ]. The use of DoE was previously reported for the optimization of MCs obtained using several techniques, such as spray-drying, phase separation, solvent evaporation and in situ and interfacial polymerization [ 25 , 26 , 27 , 28 , 29 , 30 ]. Lock et al reported on the development of a model to predict the internal architecture and mean particle diameters of gas-filled polymeric MCs, produced using phase separation [ 26 ].…”

“…The use of DoE was previously reported for the optimization of MCs obtained using several techniques, such as spray-drying, phase separation, solvent evaporation and in situ and interfacial polymerization [ 25 , 26 , 27 , 28 , 29 , 30 ]. Lock et al reported on the development of a model to predict the internal architecture and mean particle diameters of gas-filled polymeric MCs, produced using phase separation [ 26 ]. The authors considered concentration of emulsifier, stirring speed, and emulsion dilution as factors.…”