Influence of Nozzle Wettability and Surface Roughness on Liquid Jet Breakup Length

The breakup of liquid jets is ubiquitous in a wide range of industrial processes, with the breakup length widely concerned as it dictates the performance of applications such as inkjet printing, fiber manufacture, and drug delivery. However, how the nozzle properties influence the breakup length of liquid jets remains elusive. Here, we study the impact of nozzle wettability and surface roughness on the breakup length of liquid jets, using an experimental platform with reduced background noise to minimize the effect of external disturbances. Results show that the wettability of the nozzle alone has minimal influence on the jet breakup length, despite notable distinctions existing in the menisci formed at the nozzle outlet with different contact angles. An increase in surface roughness of hydrophilic nozzles is found to increase the breakup length, while for hydrophobic nozzles, the increased surface roughness decreases the breakup length. This may be because the surface roughness decreases the initial disturbance by enhancing pinning effect on the meniscus on hydrophilic nozzles, while it increases the initial disturbance when meniscus vanishes on hydrophobic nozzles. Our findings reveal the roles of nozzle wettability and roughness on liquid jet breakup, and thus, provide guidance for the practical control of jet breakup length by nozzle design.