Polarity-Dependent Electrochemically Controlled Transport of Water through Carbon Nanotube Membranes

Abstract

We demonstrate here that water can be efficiently wet and pumped through superhydrophobic aligned multiwalled nanotube membranes by application of a small positive dc bias. At a critical bias ( approximately 1.7 V), with the membrane acting as anode, there is an abrupt transition from a superhydrophobic to hydrophilic state. Interestingly, this phenomenon is strongly polarity dependent; for a negative bias applied to the membrane, 2 orders of magnitude higher bias is required for the transition. The polarity and voltage-dependent wetting that we report could be used to controllably wick fluids through nanotube membranes and could find various applications.