Electrokinetic Ion Enrichment in Asymmetric Charged Nanochannels.

Artificial bionic nanochannels have attracted wide attention and successfully used in various fields. In this work, a novel nanochannel with asymmetric surface charge is proposed to investigate the ion enrichment effect. The results show that the proposed nanochannel has excellent ion enrichment performance and the obtained ion enrichment ratio is up to 1500 when the ion concentration is 0.01 mM, which is much higher than precedent researches typically ranging from tens to hundreds. Besides, we found that the forward voltage bias will produce ions enrichment and the reverse voltage bias will produce ions depletion. The ion enrichment ratio is higher at the larger voltage bias, absolute surface charge density and smaller nanochannel height. In addition, the ion enrichment performance is more sensitive to the change of charged wall length and not sensitive to the change of uncharged wall length. The research report offers important information and instructions for the design and optimum on ion enrichment performance.