(624d) Localized Electro-Osmosis (LEO) Induced by Colloidal Motors

Experiments have shown that speed of colloidal motors decreases as the size of the motors increases. However, previous electrokinetic models have shown that the colloidal motor speed is independent of size, at least for the case of thin double layers for reaction-limited catalysis, which is the usual case observed in experiments. Why do we get conflicting results from experiments and modeling? We hypothesize that it is due to localized electro-osmotic flows at the wall, caused by the colloidal motors. Here, we propose an electrokinetic model that includes wall effects to describe the colloidal motor speed. With localized electro-osmosis, we are able to show that motor speed is dependent upon size, and the result from our model is compared to data in the literature. Also, we compare the electro-osmotic flow induced by an applied electric field with that by a self-generated electric field to distinguish situations where each is important, such as confined spaces and pores.