The facile approaches to asymmetric modification of glassy biconical microchannel wall with silver, copper or gold.

The modification of inner surface has significant influence in the properties of the nano or microchannel based on various materials, especially for the ionic current rectification (ICR) that arises from the selective interaction between ions in solution and the inner surface. Herein, we demonstrate a simple strategy to asymmetrically modify the inner wall of a glassy biconical microchannel with silver, copper or gold by means of silver mirror reaction and polydopamine platform, respectively. And the bidirectional ionic current rectification phenomena were observed in all of the modified biconical microchannels. All of the modification methods are simple, facile and low-cost, and can be applied in the modification of other glassy pipettes.