Electrospraying and electrospinning in the production of oil-based microcapsules and microfibers

Abstract

Electrospraying and electrospinning are electrohydrodynamic techniques that are applicable to the production of both capsules and fibers on a micro scale. Electrical forces are applied to the surface of the polymer solution to form a charged jet that stretches towards the collector with simultaneous solvent evaporation, forming beads (microcapsules) or microfibers with polymer coating; the morphology heavily influenced by the stability of the jet. These methods can be used to achieve carriers for biologically active hydrophobic substances, such as oils, fatty acids, and oil-soluble substances due to the fact that they do not require the use of high temperatures or toxic solvents. They enable the encapsulation of liquids in polymeric structures and limit possible oxidative degeneration of sensitive compounds. A potential application for electrosprayed microcapsules and electrospun microfibers is functional food production. Careful selection of polymers of various sources and solvents, as well as process parameters, allows for sealing the oil in the shell. The obtained products show more favorable properties in comparison with oils in the bulk, as well as capsules produced using other common encapsulation techniques. Several properties of the solutions such as their viscosity, surface tension, conductivity, and the degree of polymer chain entanglement directly influence bead or fiber formation. One of the strategies for encapsulation of oils is to disperse it in the polymer solution and use the obtained w/o emulsion as the spraying liquid. Multiple emitters are also used, in the so-called coaxial (or multiaxial) electrospraying/electrospinning. This review discusses the fundamental principles of the electrohydrodynamic processes, as well as various parameters of those techniques (related to solution properties, polymer and solvent selection, the equipment used, and the methods applied to product analysis in terms of its morphology, encapsulation efficiency, and oxidation).

Keywords

• electrospinning
• microfibers
• microcapsules
• electrospraying
• oil encapsulation