Encapsulation and suspension of hydrophobic liquids via electro‐hydrodynamics

Abstract

There are situations in which bioactive products of interest in biotechnology turn out to be hydrophobic. To reach high uniform levels of such products in water-based host fluids, such as those existing in many biological environments, one strategy consists on dividing the bioactive product into tiny micrometer (or sub-micrometer) pieces, since these are much more amenable of being uniformly dispersed and stabilized in the host fluid. On the other hand, if the bioactive product must act at specific locations, these micrometer pieces need to be hold in place, an objective that may be achieved by encapsulating them in mats of fibers. Here we demonstrate how these tasks may be accomplished by resorting to the generation and control of electrified coaxial jets of a hydrophilic liquid surrounding the hydrophobic liquid carrying the bioactive substance. When the process is carried out inside a dielectric liquid, double oil/water/oil and simple oil/water emulsions may be formed. On the other hand, when the process runs in air and a biopolymer is added to the hydrophilic liquid, then non woven mats of beaded nanofibers, encapsulating the bioactive product in the beads, are generated.

A novel direct fibre generation technique for preparing functionalized and compound scaffolds and membranes for applications within the life sciences

“…Hence, we threaded two immiscible polymeric media having a varied nanoparticulate and a nanotube concentration which was found to form threads with diameters ranging from a few hundred nanometres to a few micrometres (figures 3(a) and (b)). This effect on fibre diameter as a function of particulate loading has been observed and reported with electrospinning [29,30]. It was clear that the flow rates of media within the needles together with the applied pressure formed threads having a varied structure.…”

Stable Electrospinning of Core-Functionalized Coaxial Fibers Enabled by the Minimum-Energy Interface Given by Partial Core–Sheath Miscibility

“…The encapsulation of an industrial oil (Elf SAE-15W50) as a core inside DMF-dissolved PVP by Díaz et al 63 and Díaz Gómez et al, 62 as well as inside water-dissolved PEO by Díaz Gómez et al, 62 is interesting, as Díaz et al point out that low γ cs is required, 63 yet the oil–water interface when using aqueous PEO as sheath should have quite significant γ cs . However, the industrial oil actually contains surfactants; 63 hence, this is an example where surfactant addition is a viable means of reducing γ cs .…”

“…The original confusion remains, with different teams publishing conflicting views on the matter, both for core–sheath electrospinning and for the closely related challenge of core–sheath electrospray. Several papers reported on spinning cores and sheaths that are fully miscible, 14 , 15 , 37 , 41 , 43 − 46 , 49 , 53 , 58 , 61 , 62 some emphasizing the importance of low interfacial tension, γ cs , between the two liquids. 15 , 63 Others have maintained that cores and sheaths should be immiscible, 16 − 18 , 30 , 42 , 55 , 64 − 66 often referring to the original Li and Xia work, which even showed evidence of loss of core–sheath structure when miscible fluids were spun.…”

Surface tension effects on submerged electrosprays

“…it also permits encapsulation of substances by the combination of two liquids into the so-called "coaxial-jet electrospray" 17 . The technique has proved to be extremely efficient encapsulating substances, not only as spherical micro-capsules, but also in the shape of micro/nano-fibers [18][19][20] . An interesting perspective would be to implement such a powerful atomization technique into a microfluidic device to benefit from the enhanced control of such systems.…”