Vertically-aligned Carbon Nanotube Membranes for Breathable and Protective Fabrics
N. Bui, S. Kim, E. Meshot, J. Pena, S. Guo, K. J. Wu, F. Fornasiero*
Lawrence Livermore National Laboratory, Livermore, CA
U.S. Army Natick Soldier Research, Development and Engineering Center, Natick, MA
Membrane materials with high breathability, high degree of protection from chemical and biological (CB) agents, and rapid response to CB threats are highly desirable for protective fabrics. At LLNL, we recently proposed a CB threat responsive fabric platform based on a carbon nanotube membrane. The membrane consists of an array of a-few-nm-wide vertically-aligned carbon nanotubes (VACNTs) as through pores and a flexible, impermeable parylene-N matrix filling the inter-tube spacing. It promises to provide high water-vapor transport rate and an effective barrier function to CB agents by best leveraging the outstanding mass transport properties of narrow CNT channels. Furthermore, this membrane platform is ideally suited to fundamentally understand the mechanisms of mass transport through CNT pores.
In this work, we empirically investigated the transport properties through the well-aligned, narrow CNT channels at varied length scale. Results showed that these VACNTs membranes sustained an ultrahigh liquid and gas transport rates when compared with conventional theory predictions. Also, they performed outstanding moisture vapor transport rates (> 4000 g.m-2.day-1 at all relative humidities), comparable to or exceeding state-of-the-art breathable fabrics. Selectivity study showed that these membranes completely excluded 5-7nm-Au nanoparticles and charged 3-nm dye molecules during dead-end filtration tests. Furthermore, our membranes demonstrated bioprotection capability through size-exclusion mechanism when Dengue virus was used as a surrogate for a biological threat agent. These findings suggest that, with appropriate functionalization at the CNTs pore entrances, VACNT-polymer composite membranes may provide excellent candidates for next generation of breathable fabrics with active protection from CB threats.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.