# Cation dependent electroosmotic flow in glass nanopores

## TL;DR

This study investigates how different Group 1 cations affect electroosmotic flow in glass nanopores, revealing flow reversal phenomena and cation-dependent flow behaviors under various voltages.

## Contribution

It demonstrates the influence of specific cations on electroosmotic flow and explains flow reversal through the interaction of internal and external flows.

## Key findings

- Flow reversal observed for all salts under negative voltage
- Flow strength decreases with larger cations like Cs under negative voltage
- Unique flow reversal for Cs under positive voltage

## Abstract

We present our findings on the changes to electroosmotic flow outside glass nanopores with respect to the choice of Group 1 cation species. In contrast with standard electrokinetic theory, flow reversal was observed for all salts under a negative driving voltage. Moving down Group 1 resulted in weaker flow when the driving voltage was negative, in line with the reduction in the zeta potential on the glass surface going down the periodic table. No trend emerged with a positive driving voltage, however for Cs, flow was uniquely found to be in reverse. These results are explained by the interplay between the flow inside the nanopore and flow along the outer walls in the vicinity of the nanopore.