Microelectrophoresis in a laser trap: A platform for measuring electrokinetic interactions and flow properties within microstructures

Kahl, V.; Gansen, A.; Galneder, R.; Rädler, J. O.
July 2009
Review of Scientific Instruments;Jul2009, Vol. 80 Issue 7, p073704
Academic Journal
We describe a combination of microelectrophoresis and laser-trap methodology to accurately measure the electric force acting on a charged microsphere which is trapped in an optical tweezer. This field/trap apparatus allows measuring of the zeta potential with submillivolt accuracy and high temporal resolution. The combination with stop-flow techniques in principle provides a mean to observe adsorption or enzyme kinetics with single molecule sensitivity. We show that it is possible to accurately profile the position and frequency dependent hydrodynamic and electro-osmotic flow inside a microchannel structure of dimensions typically used in microfluidic applications without the need of fluorescent markers. We found good agreement to the theory of electrophoretic flow when retardation effects for rapidly alternating electric fields are included.


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