Wettability transparency and the quasiuniversal relationship between hydrodynamic slip and contact angle

Bladimir Ramos-Alvarado, Satish Kumar, G. P. Peterson

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Abstract

The universality of the scaling laws that correlate the hydrodynamic slip length and static contact angle was investigated by introducing the concept of the wettability transparency of graphene-coated surfaces. Equilibrium molecular dynamics simulations of droplet wettability for Si(111), Si(100), and graphene-coated silicon surfaces were performed to determine the conditions required to obtain similar contact angles between bare and graphene-coated surfaces (wettability transparency). The hydrodynamic slip length was determined by means of equilibrium calculations for silicon and graphene-coated silicon nanochannels. The results indicate that the slip-wettability scaling laws can be used to describe the slip behavior of the bare silicon nanochannels in general terms; however, clear departures from a general universal description were observed for hydrophobic conditions. In addition, a significant difference in the hydrodynamic slippage was observed under wettability transparency conditions. Alternatively, the hydrodynamic boundary condition for silicon and graphene-coated silicon nanochannels was more accurately predicted by observing the density depletion length, posing this parameter as a better alternative than the contact angle to correlate with the slip length.

Original languageEnglish (US)
Article number074105
JournalApplied Physics Letters
Volume108
Issue number7
DOIs
StatePublished - Feb 15 2016

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All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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