Pressure-Assisted Selective Preconcentration in a Straight Nanochannel

Abstract

We investigate the preconcentration profiles of a fluorescein and bovine serum albumin derivatized with this fluorescent tag in a microfluidic chip bearing a nanoslit. A new preconcentration method in which a hydrodynamic pressure is added to both electroosmotic and electrophoretic contributions is proposed to monitor the location of the preconcentration frontline. A simple predictive model of this pressure-assisted electropreconcentration is proposed for the evolution of the flow profile along this micro/nano/microfluidic structure. We show with a small analyte such as fluorescein that the additional hydrostatic pressure mode enables to stabilize the concentration polarization (CP) effect, resulting in better control of the cathodic focusing (CF) peak. For BSA (bovine serum albumin), we exhibit that the variation of the hydrodynamic pressure can have an even more drastic effect on the preconcentration. We show that, depending on this hydrodynamic pressure, the preconcentration can be chosen, either in the cathodic side or in the anodic one. For the first time, we prove here that both anodic focusing (AF) and cathodic focusing (CF) regimes can be reached in the same structures. These results also open new routes for the detection and the quantification of low abundance biomarkers.

Dielectric properties of a single nanochannel investigated by high-frequency impedance spectroscopy

“…The unbalanced ionic transport between anionic and cationic species through a nanofluidic structures initiates a polarization effect related to the concentration domain, which can be applied for focusing and locally preconcentrate ionic species. [12], [13] Compared to the classical microfluidic field, the nanometer dimension of the channel requires specific theoretical predictions and experimental discussions. [14], [15], [16], [17].…”

Theory of multi-species electrophoresis in the presence of surface conduction

“…This is of practical significance as gradients in binary electrolyte are observed during FASS and concentration polarization at the interface of a microchannel and nanochannel [13]. The latter phenomenon has found applications in shockelectrodialysis for deionization of water [10].…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2012–2014)

“…Stability of the depletion or concentration zones for as long as possible means increased enhancement factors. Louer et al demonstrated the use of external hydrodynamic pressure to achieve concentration on the anodic or cathodic side of the NMI using the same device design and demonstrated stable ICP . The 150‐nm nanochannels were made in glass.…”