Dynamic nozzles for drop generators

Abstract

In this paper, a novel mechanism allowing greater control over the formation of droplets is presented. This is achieved via the use of a dynamic nozzle of adjustable diameter. It is demonstrated that, by using such a nozzle, it is possible to greatly modify the formation and breakup of the ligament behind the main drop, leading to an overall reduction in the number of satellite droplets. Furthermore, by adjusting the delay between the beginning of the forming of the drop and the start of the nozzle constriction, a greater control over both the number of satellites and the size of the main drop can be achieved. It is also shown that only a minimal reduction of the nozzle’s effective diameter is required in order to exploit the positive effects of the technique presented here. This opens the possibility of incorporating the technique into current droplet generator systems, e.g., via the use of piezoelectric driven nozzles or other micro-mechanical actuation technology.

Experimental Investigation on the Dynamics of On-Demand Ferrofluid Drop Formation under a Pulse-Width-Modulated Nonuniform Magnetic Field

“…The studies on droplet formation from a nozzle have been started a long time before those in microfluidics. Dripping drops from a nozzle are omnipresent and play important roles in a wide range of science, industrial, and engineering applications, that is, inkjet printing, emulsion formation, 3D microprinting, medicine, and agriculture. ,− The gravity has a major effect on droplet formation from a nozzle, whereas it is usually neglected in comparison with other forces in microfluidics. The droplet pinch-off by gravity at the nozzle is the most widely used method for drop generation, due to its low cost and simplicity .…”

Drop-on-demand satellite-free drop formation for precision fluid delivery

“…In the case of DOD, finding the working conditions for the suppression of satellites for viscous fluids remains a trial-and-error process for the formation of both microlitre (Castrejón-Pita et al 2008, 2011Harris et al 2015) and picolitre drops (Wang et al 2012;Dong, Carr & Morris 2006;Kwon 2010). Castrejón-Pita et al (2015) fitted a nozzle with an iris to allow variation of the nozzle diameter in their L-drop generator in order to control the number of satellites. Their results suggest a strong correlation between the conditions required to eliminate the satellite droplet and the drop volume, which could limit the flexibility to create drops of pre-defined size.…”