Sample Preconcentration in Channels with Nonuniform Surface Charge and Thick Electric Double Layers

A. Eden [1], C. McCallum [1], B. Storey [2], C. D. Meinhart [1], S. Pennathur [1],
[1] University of California Santa Barbara, Santa Barbara, CA, USA
[2] Olin College, Needham, MA, USA
Veröffentlicht in 2016

We present a novel method for concentrating and focusing small analytes by taking advantage of the nonuniform ion distributions produced by thick electric double layers (EDLs) in nanochannels with heterogeneous surface charge. Specifically, we apply a voltage bias to a gate electrode embedded within the channel wall, tuning the surface charge in a region of the channel and subsequently altering the electric field in that region relative to the rest of the channel. The resulting field gradients "stack" charged sample ions near an interface where a step change in zeta potential occurs, providing enhancement ratios superior to those exhibited in traditional microfluidic methods. Numerical simulations are performed to demonstrate the phenomenon, and resulting velocity and salt concentration profiles show good agreement with analytical results.

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