Fabrication, Electrokinetics and Applications of Carbon Nanotube Membranes

Recently carbon nanotube (CNT) membrane has been a subject of intensive research activities due to their unique attributes, such as i) a dramatically enhanced fluid flow, ii) functional chemistry at the CNT tip entrance for effective chemical and biological separations, and iii) electrically conductive carbon nanotubes allowing for efficient electrochemical functionalization and electro-osmosis pumping.1-5 Meanwhile, the estimated overall costs of drug addiction and abuse in the United States alone exceed half a trillion dollars annually as reported by National Institute on Drug Abuse (NIDA). Classical transdermal patches for drug addiction and abuse treatments like nicotine patch can only provide constant dosing rates. However many drug abuse and addiction treatments demands variable dosing rates. Herein, a relatively low-cost microtoming method has been developed to fabricate carbon nanotube (CNT) membranes in large scale. The tips of CNT membranes were functionalized using an efficient electrochemical grafting method, following by a series of chemical coupling reactions. It was demonstrated that Ionic mobilities through CNT cores are enhanced by a factor of ~4 with a significant rectification seen for large anion/cation mixtures. High electro-osmotic flows of ~3 cm/s-V is seen for ~ 1nm single walled CNTs and ~0.15 cm/s-V for ~ 7nm multi-walled CNTs. The enhanced electrophoretic and electro-osmotic phenomenon of CNT membranes have been successfully applied to a programmed transdermal nicotine patch that can provide therapeutically useful fluxes ranging from high (1.3±0.65 µmol/hr-cm2) and to low (0.33±0.22 µmol/hr-cm2) for efficient smoking cessation treatments (in vitro (human skin) & in vivo (hairless guinea pig)).