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Deposition of pharmaceuticals by electro-aerodynamically assisted spraying (EAAS)

Berri, Nael; (2019) Deposition of pharmaceuticals by electro-aerodynamically assisted spraying (EAAS). Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The coating of engineered support substrates with proteins and other active ingredients is gaining momentum in numerous fields, such as in the chemical and pharmaceutical industries. The literature describes many coating techniques with one of the most successful being conventional electrospray (ES) deposition, which uses liquid precursors dissolved in a carrier solvent. A dry deposit is usually desired and ES, used in a “cone jet” mode has the ability to coat a support with good homogeneity, a degree of control, and little or no waste. However, one major drawback remains that the cone jet mode is often destabilized with coating formulations of high electrical conductivity (>30000 µS/m) and this in turn limits the range of formulations that can be successfully electrosprayed. The research described here is aimed towards the development of a hybrid technique for industrial use that could overcome the limiting factors of ES by combining it with another method of spray deposition that utilizes “aerodynamic assistance”. The basis of the work is an investigation into the design of a novel industrial spraying system, principally for the coating of epicutaneous patches used in the treatment of allergens, but which could be used for a host of other applications where a liquid precursor is used to coat a substrate. The hybrid process uses compressed gas passing within a chamber to form an aerodynamic sheath around a conventional ES exit nozzle setup. The liquid to be sprayed emerges from the nozzle and the gas flow envelops the air-liquid meniscus and creates a suction within the nozzle chamber giving the meniscus a shape very similar to the one obtained in a conventional electrospray cone-jet mode (with minor differences). Both the electrostatic forces (in the case of ES) and pneumatic suction (in the case of aerodynamically assisted jetting/spraying) counteract liquid surface tension and are able to refine the liquid “cone” exiting from the delivery system, and in turn lead to a jet and a spray of precursor/solvent droplets of controlled size that evaporate during and after transport to the surface, leaving behind a dry deposit. The benefit of aerodynamic assistance (on its own) is that it can replace from ES when higher conductivity fluids are employed, although there remain significant issues with process control, and with overspray and hence wastage and deposit uniformity. This thesis posits that the combination of electrospray and aerodynamically assisted jetting/spraying could eventually lead to a process which combines the benefits of both techniques, with mitigation of their deficiencies and will thus be able to generate high yields of active ingredients directly on to supports, such as epicutaneous patches.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Deposition of pharmaceuticals by electro-aerodynamically assisted spraying (EAAS)
Event: UCL (University College London)
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Licence (https://creativecommons.org/licenses/by-nc-nd/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
URI: https://discovery.ucl.ac.uk/id/eprint/10080709
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