Anomalous contact angle hysteresis of a captive bubble: Advancing contact line pinning

Siang Jie Hong, Feng Ming Chang, Tung He Chou, Seong Heng Chan, Yu Jane Sheng, Heng Kwong Tsao

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

Contact angle hysteresis of a sessile drop on a substrate consists of continuous invasion of liquid phase with the advancing angle (θa) and contact line pinning of liquid phase retreat until the receding angle (θr) is reached. Receding pinning is generally attributed to localized defects that are more wettable than the rest of the surface. However, the defect model cannot explain advancing pinning of liquid phase invasion driven by a deflating bubble and continuous retreat of liquid phase driven by the inflating bubble. A simple thermodynamic model based on adhesion hysteresis is proposed to explain anomalous contact angle hysteresis of a captive bubble quantitatively. The adhesion model involves two solid-liquid interfacial tensions (γsl > γsl′). Young's equation with γsl gives the advancing angle θa while that with γsl′ due to surface rearrangement yields the receding angle θr. Our analytical analysis indicates that contact line pinning represents frustration in surface free energy, and the equilibrium shape corresponds to a nondifferential minimum instead of a local minimum. On the basis of our thermodynamic model, Surface Evolver simulations are performed to reproduce both advancing and receding behavior associated with a captive bubble on the acrylic glass.

Original languageEnglish
Pages (from-to)6890-6896
Number of pages7
JournalLangmuir
Volume27
Issue number11
DOIs
StatePublished - 7 Jun 2011

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