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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 47: Wetting, Droplets, and Microfluidics (joint session DY/CPP)
CPP 47.2: Talk
Thursday, March 21, 2024, 15:15–15:30, BH-N 334
Investigation of nonlinear electrophoresis in microfluidics with alternating voltages — •Robert Epkenhans1, Ralf Eichhorn2, Dario Anselmetti1, and Martina Viefhues1 — 1Bielefeld University — 2Nordita Stockholm
Electrophoresis (EP) is a common phenomenon in microfluidics used for controlled migration of biomolecules like DNA or for size selective migration in gels. In the linear, low-field regime the EP-mobility is dependent only on the particle-zeta and the ambient electrolyte. Yet, recent studies reveled a polynomial velocity increasement for colloid particles exposed to high electric fields above roughly 100 kV/m with the underlying physical mechanisms still under debate.
In our studies, we quantified the nonlinear response in the mobility of charged particles in a microfluidic PDMS-chip as a function of the applied electric field strength. Therefore, we used 1) a superimposition of low DC-fields (0-13 kV/m) and high sinusoidal alternating fields up to 260 kV/m, 2) asymmetric potentials yielding a vanishing time-averaged mean, but non-vanishing higher-order mean value. We present several data sets for the particle velocities with a variation of ionic concentration and types and the respective higher-order electrophoretic mobilities. Our results suggest that nonlinear-EP forces are rather relevant in insultorbased microfluidics instead of dielectrophoresis. This opens new possibilities for particle separation devices, e.g. DNA-molecules, since the up to date data indicates size- and shape-dependent electrophoresis in the nonlinear regime. Concerning these matters, we provide suggestions for future studies on nonlinear electrophoresis.
Keywords: electrophoresis; microfluidics; colloids; zeta-potential; dielectrophoresis