Energy Loss for Droplets Bouncing Off Superhydrophobic Surfaces

Calvin Thenarianto, Xue Qi Koh, Marcus Lin, Ville Jokinen, Dan Daniel

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

A water droplet can bounce off superhydrophobic surfaces multiple times before coming to a stop. The energy loss for such droplet rebounds can be quantified by the ratio of the rebound speed UR and the initial impact speed UI; i.e., its restitution coefficient e = UR/UI. Despite much work in this area, a mechanistic explanation for the energy loss for rebounding droplets is still lacking. Here, we measured e for submillimeter- and millimeter-sized droplets impacting two different superhydrophobic surfaces over a wide range of UI (4–700 cm s–1). We proposed simple scaling laws to explain the observed nonmonotonic dependence of e on UI. In the limit of low UI, energy loss is dominated by contact-line pinning and e is sensitive to the surface wetting properties, in particular to contact angle hysteresis Δ cos θ of the surface. In contrast, e is dominated by inertial-capillary effects and does not depend on Δ cos θ in the limit of high UI.
Original languageEnglish (US)
JournalLangmuir
DOIs
StatePublished - Feb 16 2023

ASJC Scopus subject areas

  • Spectroscopy
  • General Materials Science
  • Surfaces and Interfaces
  • Electrochemistry
  • Condensed Matter Physics

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