High angle mass flux of an electrospray plume

Abstract High-resolution mass flux measurements of an electrospray plume are reported at high (&gt;30 $$^{\circ }$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> ) angles, which are relevant to direct impingement of downstream electrodes. Interrogation of the plume edge greatly reduces uncertainty in electrospray device lifetime estimation related to mass flux to electrode surfaces. An angularly-actuated Thermoelectric Quartz Crystal Microbalance (TQCM) provides resolution down to $$\sim$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> </mml:math> 2 pg cm $$^{-2}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> s $$^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> , allowing the highest resolution mass flux measurements of an electrospray plume to be reported herein. In-situ microscopy of the electrospray meniscus revealed changes to the electrode lines-of-sight of approximately 2°–3° due to the increasing meniscus tip height with beam current. Using the TQCM measurements and previous QCM results, a data-driven model is proposed for estimating electrode impingement as a function of beam current and aperture line-of-sight, which quantitatively captures the rapid increase in mass flux at higher beam currents or at low angles. The results show it is possible to guarantee negligible electrode impingement within a specified range of throttle levels.