Coalescence of sessile droplets of varying viscosities for line printing

Min Wook Lee, Na Young Kim, Sanjeev Chandra, Sam S. Yoon

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Coalescence of sessile droplets is studied experimentally with water-glycerin mixtures of different viscosities. Effects of viscosity on the dimensionless spreading length (Ψ) and the center-to-center distance (L) are investigated for two droplets; the first droplet (Ds) is stationary on a substrate and the second droplet (D0) landing at a center-to-center distance L from the first droplet. For a low viscosity fluid, Ψ is maximum when L approaches zero (or λ→1, where λ=1-L/Ds), which represents a head-on collision. For a high viscosity fluid, Ψ is minimum when λ→0.6. The effect of λ on line printing for various viscosities is also examined by printing multiple droplets. We found that the larger the viscosity, the less the breakup between droplets; viscosities smaller than 60wt% glycerin yielded line breakup. The overlap ratio of λ>0.3 produced not a line, but a bigger droplet or puddle because of coalescence. Data obtained in this work can provide insights for the fabrication of conductive microtracks or microinterconnects in printed-electronics applications where a line breakup between droplets would lead to an electrical circuit short.

Original languageEnglish
Pages (from-to)138-148
Number of pages11
JournalInternational Journal of Multiphase Flow
Publication statusPublished - 2013 Oct


  • Coalescence
  • Droplet impact
  • Line printing
  • Spreading
  • Viscosity
  • Wettability

ASJC Scopus subject areas

  • Mechanical Engineering
  • Physics and Astronomy(all)
  • Fluid Flow and Transfer Processes


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