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Hysteresis and interfacial energies in smooth‐walled microfluidic channels
Author(s) -
Liu Yihong,
Nolte D. D.,
PyrakNolte L. J.
Publication year - 2011
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2010wr009541
Subject(s) - wetting , contact angle , hysteresis , materials science , imbibition , microfluidics , capillary action , saturation (graph theory) , capillary pressure , surface energy , adsorption , surface tension , porous medium , porosity , composite material , nanotechnology , thermodynamics , chemistry , condensed matter physics , physics , germination , botany , mathematics , combinatorics , biology
Hysteresis in the capillary pressure‐saturation relationship ( P c – S w ) for a porous medium has contributions from the complex geometry of the pore network as well as the physical chemistry of the grain surfaces. To isolate the role of wettability on hysteresis, we fabricated microfluidic cells that contain a single wedge‐shaped channel that simulates a single pore throat. Using confocal microscopy of the three‐dimensional interfaces under imbibition and drainage, we demonstrate an accurate balance between mechanical work and surface free energy that was evaluated using measured advancing and receding contact angles. The closed‐loop mechanical work per surface water molecule is 95 kJ/mol, which is consistent with physisorption. Therefore, the hysteresis in the P c – S w relationship for a single pore throat is defined by advancing and receding contact angles that are controlled by dissipative surface adsorption chemistry.