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

27 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

Bibliographical note

Funding Information:
This work was supported by the Human Resources Development of the Korea Institute of Energy Technology Evaluation and Planning (KETEP, No. 20124030200120), and the Converging Research Center Program through the Ministry of Education, Science and Technology ( 2010K000969 ).


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

ASJC Scopus subject areas

  • Mechanical Engineering
  • General Physics and Astronomy
  • Fluid Flow and Transfer Processes


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