Modeling of a Novel Multi-Jet Emitter for ESI-MS Applications

This paper presents the concept and simulation of a novel multiple electrospray emitters for electrospray ionization mass spectrometric (ESI-MS) applications. The proposed emitter is based on an array of carbon nanofibers (CNF) vertically grown around the orifice of a microscale thermoplastic capillary. The electrospray ionization process is simulated using a CFD code that utilizes Taylor-Melcher leaky-dielectric formulations for the electrohydrodynamics and volume-of-fluid (VOF) method for tracking the interface. The modeling results predict that under steady state conditions, individual cone-jets are established around each of the CNFs resulting in an array of electrosprays. Effects of several design and operational parameters on the electrospray performance are thoroughly investigated. The results of the present study will facilitate design, fabrication and experiments using the CNF emitter. Higher spray current and lower jet diameter indicate that the proposed emitter can perform equivalent to nanospray emitters exhibiting improved MS sensitivity while using a microscale orifice. Use of microscale orifice benefits in terms of higher sample throughput and eliminates potential clogging problem inherent in nanoscale capillaries. Overall, the proposed emitter is believed to be a suitable candidate for ESI-MS applications.