AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Preventing the Spray Break-up in Electrohydrodynamic Atomization
CHRISTIAN LUEBBERT, Jan Marijnissen, Wolfgang Peukert, FAU Erlangen-Nuremberg, Germany
Abstract Number: 286 Working Group: Instrumentation and Methods
Abstract Electrohydrodynamic atomization is a process, where a liquid is disintegrated into small droplets under the influence of electrical stress. The mostly used cone-jet-mode is well understood and known to produce almost mono-dispersed particles as an outstanding property [1]. With this type of electrospray, the droplets emitted from liquid jets are strongly affected by the space charge. Therefore, the initially well aligned particle beam, emitted from the liquid jet under axial break-up conditions, spreads up into the typical spray-cone. This seemingly inevitable behavior prevents in practice the patterned deposition of the electrosprayed particles. Recent strategies in direct pattern formation from electrosprays have shown to be limited in mono-dispersity, precision of the deposition and might as well suffer from the plugging risk due to the small capillaries used (e.g.[2]).
We propose a robust and easy to clean setup, in which the spraying process is carried out under modified conditions. The resulting spraying mode produces highly mono-disperse microdroplets at a constant emission frequency under conditions of a constant volumetric flow rate and dc voltage. The break-up of the spray-cone can be prevented resulting in perfectly aligned particle chains for comparably long distances in the cm-range. Hence, an operation mode for well-defined pattern deposition was found.
The influence of the applied voltage and the volumetric flow-rate on the emission frequency will be discussed in detail. Requirements on the liquid and limitations on the obtainable particle size will be shown for various liquids. Experimental results are discussed in comparison to theoretical predictions based on analytical estimations for the interactions between the spray and the external electric field.
[1] Ganan-Calvo, A. M.; Davila J.; Barrero, A. J. Aerosol Sci. 1997 (28) No. 2, pp. 249-275.
[2] Schirmer, N. C.;Ströhle, S.; M. K. Tiwari, M. K.; D. Poulikakos D. Adv. Funct. Mater. 2011 (21), pp. 388–395.