Electro hydrodynamic atomization: An emerging technique

Electrohydrodynamic atomisation (EHDA) is an emerging technique for the production of micron and nano-scaled particles. The process often involves Taylor cone enablement, which results in a fine spray yielding formulated droplets, known as electrospraying, which then undergo drying during deposition.

Multi tip devices have been designed and engineered to be utilised in potential up-scaled EHDA, in comparison to the traditional single needle system.

Figure 1: EHDA jetting examples from a single nozzle system showing: (a) Formulation flow with no applied voltage – dripping; (b) Unstable jetting; (c) Stable jetting – Taylor cone; (d) Multiple-jets from a single nozzle. (e) The coaxial nozzle system used for jetting with two co-flows (Inner and outer nozzles). 

The physical properties of solutions used in this technique have an undeniable impact on the particles formed. The physical characteristics of the solutions are, but not limited to, viscosity (Dependent on polymer concentration); surface tension and electrical conductivity. The properties can be manipulated to result in the sister technique of electrospinning, the formation of fibers, as oppose to particles with electrospraying.

Multiple characterization techniques can be applied to this engineering technique in order to ensure desired particles are formed, these are but not limited to: differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM).

The applications of EHDA are vast and have demonstrated high potential in both the pharmaceutical and biomedical field. Most recently, research into the use of EHDA and polymer solutions to create drug delivery systems has been extremely popular worldwide. Furthermore, research into its utilization in food science is fast emerging. As a result, the advantages of this one step engineering method have overcome limitations faced in these sectors.