Aerosol Production by Vibrating Membrane Technology: Analysis of the Electrolyte Effect on Generated Droplet Size and Nebulizer Output Rate

The performance of vibrating membrane technology (i.e., aerosol droplet size and output rate) depends on the specific electrolyte concentration. However, the underlying factors, which determine nebulizer performance, are currently only poorly understood. This study compared the charge of aerosol droplets (Dekati® BOLAR™) nebulized with the eFlow® rapid and the streaming potential (SurPASS®) forming at the liquid/metal interface. Nebulization of 0.01 mM sodium chloride resulted in a rather large droplet size of >8 μm and an output rate of only ∼0.4 g/min. Increasing the sodium chloride content to 10 mM led to a droplet size of <5 μm and an output rate of ∼1.0 g/min. No significant difference was detected when comparing the net charge-to-mass ratios of generated aerosols. In contrast, the streaming potential (i.e., adversary of droplet detachment) differed remarkably between the 2 electrolyte solutions. The higher salt concentration compensated the electrical potential difference formed at the liquid/metal interface and, thus, caused an increased output rate (and a delivery of smaller aerosol droplets). Overall, this study identified the streaming potential as a significant parameter with impact on vibrating membrane nebulizer performance. The presented results will promote progress in this specific subfield of aerosol drug delivery.