Electrospray characterization based on an emitter of cone-shaped porous medium for the high-throughput microliter aerosol generation

Abstract

A compact electrospray system has been developed using a cone-shaped porous medium. The cone-jet conditions with a stable spraying mode were measured using ethanol and lavender oil, and the average diameter and size distribution of the sprayed droplets were investigated according to the applied voltage. In addition, the spray stability over time was analyzed because the fluid was supplied with a capillary action without the use of a pump. The average diameter of the droplets was 3.6-6.7 mu m (ethanol) and 6.4-8.6 mu m (lavender oil). We observed that the average particle size clearly increased with the applied voltage; the cause was determined based on the electric stress due to the potential difference ("electric pressure") between the tip of the porous medium and ground ring. Moreover, the mean droplet size according to the electrical potential was proportional to E-0.5 (ethanol) and E-0.85 (lavender oil). The penetration time in the porous medium of the proposed system was controlled by the physical properties of the fluid, such as surface tension and viscosity, and affected the spray stability when spraying for a long time. Thus, the spray stability could be improved by controlling the applied voltage in the cone-jet mode region.