title: Ambient pressure effects on the electrokinetic potential of Zeonor-water interfaces.
abstract: Using phase-sensitive streaming potential experiments in a vacuum chamber, we demonstrate that lowering the ambient pressure of the air surrounding a hydrophobic, Zeonor microfluidic substrate results in a decrease in the time scale required for equilibration of the electrokinetic potential. At ambient air pressures below 0.74 atm, the electrokinetic potential changes from ∼-84 mV to ∼-11 mV in 5 h, while the same decrease occurs in a period of over 200 h when the system is at 1 atm. Returning a sub-atmospheric system (where the electrokinetic potential had equilibrated to -11 mV) to atmospheric pressure did not result in any additional change in the electrokinetic potential. This can be described as a type of hysteresis of the electrokinetic potential with dissolved gas concentration. No time or pressure dependence was observed for the electrokinetic potential of hydrophilic (silica) substrates.
authors.affiliation: Department of Biomedical Engineering, Cornell University, United States.
authors.forename: Vishal
authors.initials: V
authors.lastname: Tandon
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Kirby
mesh_terms: D001274:Atmospheric Pressure; D003516:Cycloparaffins / Q000737:chemistry*; D046209:Electrophoresis, Microchip / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D011312:Pressure; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D003516:Cycloparaffins; D014867:Water