Dramatic transport properties of carbon nanotube membranes for a robust protein channel mimetic platform

Carbon nanotube (CNT) membranes offer an exciting opportunity to mimic natural protein channels due to (1) a mechanism for dramatically enhanced fluid flow, (2) ability to place 'gatekeeper' chemistry at the entrance to pores, and (3) being electrically conductive to localize electric field or perform electrochemical transformations. The transport mechanisms through CNT membranes are primarily (1) ionic diffusion near bulk expectation, (2) gas flow enhanced 1-2 orders of magnitude primarily due to specular reflection, and (3) fluid flow 4-5 orders of magnitude faster than conventional materials due to a nearly ideal slip-boundary interface. Transport can be modulated by 'gatekeeper' chemistry at the pore entrance using steric hindrance, electrostatic attraction/repulsion, or biochemical state. Electroosmotic flow is seen to be highly power efficient and can act as a pump through regions of chemical selectivity. The fundamental requirements of mimicking protein channels are present in the CNT membrane system. This membrane structure is mechanically far more robust than lipid bilayer films, allowing for large-scale chemical separations, delivery or sensing based on the principles of protein channels. Applications ranging from water purification, energy generation and bio-separations are highlighted. (C) 2011 Elsevier Ltd. All rights reserved.