Spreading of an inkjet droplet on a solid surface with a controlled contact angle at low weber and Reynolds numbers

Yangsoo Son, Chongyoup Kim, Doo Ho Yang, Dong June Ahn

Research output: Contribution to journalArticle

110 Citations (Scopus)

Abstract

Even though the inkjet technology has been recognized as one of the most promising technologies for electronic and bio industries, the full understanding of the dynamics of an inkjet droplet at its operating conditions is still lacking. In this study, the normal impact of water droplets on solid substrates was investigated experimentally. The size of water droplets studied here was 46 μm and was much smaller than the most of the previous studies on drop impact. The Weber number (We) and Reynolds number (Re) were 0.05-2 and 10-100, respectively, and the Ohnesorge number was fixed at 0.017. The wettability of the solid substrate was varied by adsorbing a self-assembled monolayer of octadecyltrichlorosilane followed by the exposure to UV-ozone plasma. The impact scenarios for low We impacts were found to be qualitatively different from the high to moderate We impacts. Neither the development of a thin film and lamella under the traveling sphere nor the entrapment of small bubbles was observed. The dynamics of droplet impact at the conditions studied here is found to proceed under the combined influences of inertia, surface tension, and viscosity without being dominated by one specific mechanism. The maximum spreading factor (β), the ratio of the diameter of the wetted surface and the drop diameter before impact, was correlated well with the relationship In β = 0.090 In We/(fs - cos θ) + 0.151 for three decades of We/(fs - cos θ), where θ is the equilibrium contact angle, and f s is the ratio between the surface areas contacting the air and the solid substrate. The result implies that the final shape of the droplet is determined by the surface phenomenon rather than fluid mechanical effects.

Original languageEnglish
Pages (from-to)2900-2907
Number of pages8
JournalLangmuir
Volume24
Issue number6
DOIs
Publication statusPublished - 2008 Mar 18

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Colloid and Surface Chemistry

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