Design, realization, and functional characterization of a plasma source for electrospray processes

Electrospray (EHDA) is a liquid atomization process involving the formation of very fine liquid droplets from bulk liquid under the influence of high voltage, typically of the order of kilovolts. The bulk liquid droplet is broken into fine liquid droplets of identical charge which helps their dispersion. The stable mode configuration of EHDA is pivotal to achieving a unimodal size droplet distribution. It is particularly desirable in drug delivery since monodispersity provides more controlled and reproducible release profiles, which may be more easily customized for a desired application. Furthermore, the size affects cellular uptake and thus uncontrolled size distribution could lead to different biological responses. When water is employed in the electrospray, very high voltages (in the order of kV) are required to overcome the high surface tension and permittivity, hence a corona discharge is usually ignited. This may in turn introduce instabilities and disturb the electrospray process. Usually, this is the reason why water is avoided as a working fluid, but, during the traineeship, the aim was to explore anyway the possibility to achieve a stable water electrospray with plasma discharge generation. The reason for trying to achieve a micro to nano-sized monodisperse mist is to maximize the surface-to-volume ratio exchanges between self-dispersed droplets and the gaseous plasma species, in this way is possible to enhance the production of plasma-treated water (PTW). During the electrospray, the water is activated by the plasma discharges, which generate intense UV radiation, and reactive species which are effective agents against many biological and chemical matter. This makes the PTW particularly suitable for decontamination and sterilization purposes. The thesis project has been focused on the development of a new plasma-aerosol system based on the electrospray principle and its characterization.