title: Measurement of electroosmotic and electrophoretic velocities using pulsed and sinusoidal electric fields.
abstract: In this work, we explore two methods to simultaneously measure the electroosmotic mobility in microchannels and the electrophoretic mobility of micron-sized tracer particles. The first method is based on imposing a pulsed electric field, which allows to isolate electrophoresis and electroosmosis at the startup and shutdown of the pulse, respectively. In the second method, a sinusoidal electric field is generated and the mobilities are found by minimizing the difference between the measured velocity of tracer particles and the velocity computed from an analytical expression. Both methods produced consistent results using polydimethylsiloxane microchannels and polystyrene micro-particles, provided that the temporal resolution of the particle tracking velocimetry technique used to compute the velocity of the tracer particles is fast enough to resolve the diffusion time-scale based on the characteristic channel length scale. Additionally, we present results with the pulse method for viscoelastic fluids, which show a more complex transient response with significant velocity overshoots and undershoots after the start and the end of the applied electric pulse, respectively.
authors.affiliation: CEFT, Departamento de Engenharia Mecânica, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal.
authors.forename: Samir H
authors.initials: SH
authors.lastname: Sadek
authors.affiliation: CEFT, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal.
authors.forename: Francisco
authors.initials: F
authors.lastname: Pimenta
authors.affiliation: CEFT, Departamento de Engenharia Mecânica, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal.
authors.forename: Fernando T
authors.initials: FT
authors.lastname: Pinho
authors.affiliation: CEFT, Departamento de Engenharia Química, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal.
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Alves
mesh_terms: D004058:Diffusion; D004560:Electricity; D053841:Electroosmosis / Q000379:methods*; D004586:Electrophoresis / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D008962:Models, Theoretical; D010316:Particle Size; D011137:Polystyrenes / Q000737:chemistry; D012212:Rheology / Q000379:methods
chemical_list: D011137:Polystyrenes
keywords: Electroosmotic mobility; Electrophoretic mobility; Particle tracking velocimetry; Zeta-potential measurement