Experimental study on electrospray modes and steady spray characteristics with multiple metal capillaries

Electrospray is an atomization process, in which the liquid is broken byelectrical forces. It's applied widely in nano-material preparation,mass-spectrometer, et al. Coupled with MEMS fabrications, multi-emitterelectrospray attracts great attention for its high output, integration andminiaturization.In this study, both single and multiple emitter electrospray apparatus areset up based on traditional metal capillaries to study the spray modes andsteady spray characteristics. Two of the crucial behaviors are comparedbetween the two setups, the onset voltage (V_C) of ``cone-jet'' spray modeand the relationship between electrical current (I) and flow rate (Q).Though the capillary configuration influences the spray states on differentneedles, V_C and I for both setups are proportional to \sqrt \cos \theta (\theta is the cone degree) and Q^1/2,respectively. It implies that the resulted jet is affected mainly by ratherthe local electrical distribution around the cone-jet transition region,than the external global conditions. The further electrospray withmicro-fabricated multi-emitter arrays can be supported by these results.