Determination of microcapsule physicochemical, structural, and mechanical properties

Abstract

a b s t r a c tResearch into the fundamental properties of microcapsules and use of the results to develop a wide variety of products in industries such as printing, fast-moving consumer goods, construction, pharmaceuticals, and agrochemicals is a dynamic and ever-progressing field of study. For microcapsules to be effective in providing protection from harsh environments or delivering large payloads, it is essential to have a good understanding of their properties to enable quality control during formulation, storage, and applications. This review aims to outline the commonly used techniques for determining the physicochemical, structural, and mechanical properties of microcapsules, and highlights the interlinked nature of these three areas with respect to the end-use industrial application. This review provides information on techniques that are well supported in the literature, and also examines microcapsule analytical techniques that will become more prevalent as a result of new technological developments or extensions from other areas of study.

Characterization of Core-Shell Alginate Capsules

“…The average diameter of alginate capsules ranged from 1.9 to 2.6 mm depending on curing time (significant differences at p < 0.05), with a size polydispersity lower than 10% (data not shown). Other authors also found that microcapsules produced using microfluidics had extremely narrow size distributions [24]. Using droplets millifluidic process, capsule size depends on droplet dimension before getting into contact with the alginate phase, droplet dimension depending on both the internal diameter of the Teflon tube (which was constant and equal to 1.57 mm throughout the experimental assays) and the dispersed over continuous flow rates ratio (also constant and equal to 0.4).…”

“…Elastic characteristics such as Young modulus are calculated from the initial slope of the force-displacement curve by means of different approaches (e.g. Hertz model) [15,24,29,30]. The advantage of single-bead measurement consists in detailed information of a single object and variations between beads of one production batch can be thoroughly analyzed.…”

“…The advantage of single-bead measurement consists in detailed information of a single object and variations between beads of one production batch can be thoroughly analyzed. Otherwise, it is time consuming to collect substantial, statistical significant data [24,31].…”

Designing biopolymer microgels to encapsulate, protect and deliver bioactive components: Physicochemical aspects

“…Microgel particles are typically semi-solid materials with both solid-like and liquidlike characteristics. The rheology of an individual microgel particle can be characterized by the relationship between the applied stress (force per unit area) and the resulting strain (normalized deformation) [160,161]. The initial slope of a plot of stress versus strain provides information about the elastic modulus, which is related to particle softness or hardness.…”

“…The rheology of microgel particles can be manipulated by controlling the type and concentration of biopolymer and cross-linking agents used[160,162]. Analytical approaches for measuring the rheology of individual microgel particles have been reviewed, and include methods such as deformation in shear flow, optical tweezers, micromanipulation, and atomic force microscopy[161,163].…”