Facile real-time evaluation of the stability of surface charge under regular shear stress by pulsed streaming potential measurement

Self-assemblies of polyelectrolytes have been widely used to tailor surface charges, but their stability varies significantly due to the diverse properties of both polyelectrolytes and surfaces. Fast and reliable evaluation of the stability of the assembled layers is essential to optimize the assembling processes and select the proper working conditions. In this work, the applicability of the pulsed streaming potential measurement for real-time evaluation of stability of assembled layers was demonstrated. Polyethyleneimine (PEI) with a molecular weight of 1800 was selected as the model polyelectrolyte and the results confirmed the dependence of the stability of the assembled layers on the assembling conditions. A parameter SR, which is defined as the relative zeta potential change rate, was adopted to reflect the difference of the positively charged layer. Effect of assembling conditions, including pH, polyelectrolyte concentration and contact time, on the change of the streaming potential were evaluated based on SR values. The feasibility of the technique for the evaluation of the stability of adsorbed proteins, oligonucleotides and cells onto the formed PEI layer was also investigated and its reliability was confirmed by capillary electrophoresis.