SUMMARY

The Array of Micromachined UltraSonic Electrospray (AMUSE) ion source aims to eliminate many of the limitations of conventional electrospray ion sources utilized in mass spectrometry. By decoupling analyte charging and ion formation, AMUSE provides a unique tool for exploring the mechanisms of analyte ionization. Analyte charging through electrochemically introduced ions and protonation by the addition of a weak acid will be investigated utilizing computational fluid dynamics simulations and mass spectrometry experiments of the associated ion transport phenomena. Initial tests have shown, through the application of an electric field, charge separation within the fluid reservoir will allow for the ejection of increasingly charged droplets, improving signal. Electrohydrodynamic models of increasing complexity will be used to capture the effects that Maxwell stresses, induced by electric field, have on the evolving fluid interface, droplet charge density, and ejection mode. Experimental characterization of the ejection phenomena, using stroboscopic visualization, and mass spectrometric signal under these electric fields will complete the investigation of analyte charging mechanisms and droplet ejection in the presence of an electric field. These investigations will enable the development of an ejection regime map based on relevant parameters and design and operating guidelines for improved operation of the novel AMUSE ion source.