Surfactant‐induced electroosmotic flow in microfluidic capillaries

Abstract

Control of EOF in microfluidic devices is essential in applications such as protein/DNA sizing and high-throughput drug screening. With the growing popularity of poly(methyl methacrylate) (PMMA) as the substrate for polymeric-based microfludics, it is important to understand the effect of surfactants on EOF in these devices. In this article, we present an extensive investigation exploring changes in EOF rate induced by SDS, polyoxyethylene lauryl ether (Brij35) and CTAB in PMMA microfluidic capillaries. In a standard protein buffer (Tris-Glycine), PMMA capillaries exhibited a cathodic EOF with measured mobility of 1.54 ± 0.1 (× 10⁻⁴ cm²/V.s). In the presence of surfactant below a critical concentration, EOF was independent of surfactant concentration. At high concentrations of surfactants, the electroosmotic mobility was found to linearly increase/decrease as the logarithm of concentration before reaching a constant value. With SDS, the EOF increased by 257% (compared to buffer), while it was decreased by 238% with CTAB. In the case of Brij35, the electroosmotic mobility was reduced by 70%. In a binary surfactant system of SDS/CTAB and SDS/Brij35, addition of oppositely charged CTAB reduced the SDS-induced EOF more effectively compared to nonionic Brij35. We propose possible mechanisms that explain the observed changes in EOF and zeta potential values. Use of neutral polymer coatings in combination with SDS resulted in 50% reduction in the electroosmotic mobility with 0.1% hydroxypropyl methyl cellulose (HPMC), while including 2% poly (N,N-dimethylacrylamide) (PDMA) had no effect. These results will potentially contribute to the development of PMMA-based microfluidic devices.

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high‐voltage

“…As the condition of the electroosmotic flow can be changed by CTAB , in order to maximize the ions selectivity, a BGE containing His/MES and CTAB was prepared in different proportions to investigate its effect on separation quality. Since the two microchips are made of the same material, here we still use the bent channel to experiment.…”

Zeta Potential of Poly(methyl methacrylate) (PMMA) in Contact with Aqueous Electrolyte–Surfactant Solutions

“…12 Here, the control of the electroosmotic flow (EOF) is important to obtain an accurate analysis, especially in polymeric substrates. [13][14] Furthermore, it is desirable to tune the surface chemistry of the channel substrate to suppress any analyte-wall interactions in order to improve resolution and reproducibility. 6,8 In this regard, several techniques have been proposed to manipulate EOF including altering the background electrolyte (pH and ionic strength) and permanent and dynamic coating.…”

“…6,8 In this regard, several techniques have been proposed to manipulate EOF, including altering the background electrolyte (pH and ionic strength) and permanent and dynamic coating. 6,8,14 Among these techniques, dynamic coating is perhaps the most convenient way to control EOF and analyte−wall interactions. It consists of the addition of surface-active polymers or surfactants to the system that can cause suppression, decrease, or increase of the EOF, as well as a change of the substrate wettability.…”

“…33 We choose poly(methyl methacrylate) (PMMA) as a model substrate, since it is extensively used in microfluidics, because of its good mechanical, electrical, and optical properties. 14,34 The ZP of PMMA in aqueous electrolytes, without the addition of surfactants, was extensively investigated in our previous work. 35 Here, we investigate the influence of anionic, cationic, and zwitterionic surfactants.…”

Simultaneous Determination of Inorganic Cations and Anions in Microchip Electrophoresis Using High-voltage Relays

“…As the condition of the electroosmotic flow can be changed by CTAB, [15][16][17][18] in order to attain the best selectivity, a BGE containing His/MES and CTAB was prepared in different proportions to investigate its effect on separation quality. The His/MES concentration was fixed at 20 mM, and the CTAB concentration ranged from 0 to 1 mM (0, 0.01, 0.05, 0.1, 0.5, 1 mM).…”