Ion Diffusion Upon Concentrations in Open Nanofluidic Channels

The ion flow in nanochannels is investigated by using nanochannels in an open configuration that allows the direct observation of fluid diffusion through an optical microscope. An “open nanochannel” is a channel with the top open to air such that fluidics can be introduced from both the entrance and the top of the channels. The experimental results showed that the diffusion length of the potassium chloride and phosphate buffer decreased with their concentration. The observed behaviors were analyzed by the contact angle variation due to the electrowetting phenomena involving the interaction between electrical double layer and counter-ions in the solution.