Low-voltage electrohydrodynamic (EHD) spray drying of respirable particles

Area of Science:

• Pharmaceutical Engineering
• Materials Science
• Chemical Engineering

Background:

• Traditional spray drying yields powders with broad, uncontrolled particle size distributions.
• Electrohydrodynamic (EHD) atomization offers enhanced control over particle size and morphology in spray drying.
• Conventional EHD spray drying requires droplet discharging to prevent Rayleigh breakup, adding complexity and hindering electric field collection.

Purpose of the Study:

• To introduce a novel electrohydrodynamic (EHD) spray drying setup utilizing a low-voltage nozzle.
• To demonstrate the capability of this new setup to produce pharmaceutical powders with tailored particle size and morphology.
• To characterize the performance of the low-voltage EHD spray dryer regarding particle characteristics, output, and yield.

Main Methods:

• Development of a novel EHD spray drying apparatus featuring a low-voltage nozzle.
• Characterization of the spray-dried particles for size distribution and morphology.
• Evaluation of the process output and yield of the developed EHD spray dryer.
• Utilizing an auxiliary electric field for controlled collection of moderately charged particles.

Main Results:

• The low-voltage EHD nozzle imparts moderate droplet charge, obviating the need for discharging.
• Generated pharmaceutical powders exhibit a very narrow particle size distribution.
• The process allows for the production of both porous and completely spherical particles.
• A yield of 20% was achieved, comparable to conventional small-scale spray dryers.
• An effective output of 75 mg/hr of dry powder was demonstrated with five nozzles.

Conclusions:

• The novel low-voltage EHD spray drying setup simplifies the process by eliminating the need for droplet discharging.
• This method provides precise control over particle size and morphology, producing narrow distributions.
• The ability to collect charged particles using an electric field enhances process efficiency.
• The technology is scalable, with nozzle repulsion preventing coalescence and allowing for increased nozzle density.