AC and DC microelectrophoresis of non-aqueous colloidal suspensions of controllable charge*

Non-aqueous density- and refractive-indexed matched colloidal suspensions have been very important in colloidal self-assembly [1], including recent work on colloids with dipolar and depletion interactions [2]. Electrophoresis is a powerful tool to determine the surface potential and charge of the colloidal suspension under study. However, because of refractive index matching, standard electrophoresis measurements are not possible. We carry out microscope-based micro-electrophoresis in order to measure particle charge for a range of solvent conditions.

We use the suspension of PMMA in CHB and cis-trans decalin for this study. A detailed depth analysis of the mobility of the system is conducted. Microelectrophoresis experiments are carried out in DC mode and in AC mode as a function of frequency to test for the electrode polarization effect. We find limited evidence for the electrode polarization effect. We examine microelectrophoresis in this system with varying salt concentrations.

References

[1]  Yethiraj, A., van Blaaderen, A. A colloidal model system with an interaction tunable from hard sphere to soft and dipolar. Nature 421, 513-517 (2003). https://doi.org/10.1038/nature01328

[2]  Semwal, S., Yethiraj, A., Tunable colloids with dipolar and depletion interactions: towards field-switchable crystals and gels, Physical Review X, accepted (2022)