Electroosmotic Flow of Sequence-Defined Polyelectrolyte Solutions in Charged Nanochannels: The Dominant Role of Charge Configuration.

Abstract

Nanoscale electroosmotic flow (EOF) of polyelectrolyte solutions is essential in understanding biological phenomena and developing biotechnologies. However, the lack of understanding of EOF in nanoconfined polyelectrolyte solutions is not conducive to developing these technologies. Here, a charge-configuration sensitive EOF of sequence-defined polyelectrolyte solutions in oppositely charged nanochannels is reported using an advanced dissipative particle dynamics approach, reaching a ≈100% difference in the central velocity between two charge configurations. Specifically, the average EOF velocity v_avg of ABA solutions responds linearly to surface charge density, while AB and BAB solutions show nonlinear responses. Even at zero surface charge density, a considerable net EOF is observed due to PE chain conformations. v_avg of all solutions exhibits non-monotonic behavior with increasing chain stiffness. v_avg decreases consistently with monomer density and chain length but to varying degrees, while increasing with more chain blocks as PE chains get more coiled. As charge fraction rises, v_avg of ABA solutions decreases to the fully charged case, while AB and BAB solutions show non-monotonic trends. The differences in v_avg are gradually screened by added salt. The findings of this study improve the understanding of EOF of complex fluids and can potentially help develop a new nanofluidic pumping system.