Ion Transport in 2-NM Nanochannels

In this paper, we report ion transport in 2-nm-deep nanochannels. These nanochannels are formed by controlled dry etching in silicon wafer and following anodic bonding with pyrex substrate. Our results show that surface charge dominates ion transport in these channels at concentration up to 100 mM. Due to geometry confinement effect, these nanochannel take ultra long time to reach a steady state, 3 or 4 magnitude longer than bulk diffusion. Conductance data at different ionic concentrations are compared with simulation results from a one dimensional model that accounts for salt & pH-dependent surface charge. Difference between model and experimental data indicates that proton mobility at low concentration is one magnitude higher than bulk mobility while Na⁺/K⁺ mobility doens’t change at this length scale.