Surfactant-induced electroosmotic flow in microfluidic capillaries.

Area of Science:

• Microfluidics
• Surface Chemistry
• Polymer Science

Background:

• Electroosmotic flow (EOF) control is vital for microfluidic applications, including protein/DNA sizing and drug screening.
• Poly(methyl methacrylate) (PMMA) is increasingly used in microfluidics, necessitating an understanding of surfactant effects on EOF within PMMA capillaries.

Purpose of the Study:

• To investigate the impact of anionic (SDS), nonionic (Brij35), and cationic (CTAB) surfactants on EOF in PMMA microfluidic capillaries.
• To explore the combined effects of binary surfactant systems and neutral polymer coatings on EOF in PMMA devices.

Main Methods:

• Measurement of EOF mobility in PMMA capillaries using Tris-Glycine buffer.
• Systematic addition of SDS, Brij35, and CTAB at various concentrations to assess their individual and combined effects on EOF.
• Evaluation of neutral polymer coatings (HPMC, PDMA) in conjunction with SDS to modulate EOF.

Main Results:

• Surfactant concentration significantly alters EOF; SDS increased EOF by 257%, CTAB decreased it by 238%, and Brij35 reduced it by 70%.
• Binary surfactant systems showed that oppositely charged CTAB was more effective than nonionic Brij35 in reducing SDS-induced EOF.
• Neutral polymer coatings like HPMC reduced EOF by 50%, while PDMA had no significant effect.

Conclusions:

• Surfactants exert significant and concentration-dependent control over EOF in PMMA microfluidic devices.
• The choice of surfactant (anionic, cationic, nonionic) and their combinations can be used to tune EOF for specific microfluidic applications.
• This research provides insights into optimizing PMMA-based microfluidic systems through surface modification for enhanced performance.