Automated Platform for Investigating Aligned Carbon Nanotube Films*

The one-dimensional nature of single-wall carbon nanotubes (SWCNTs) creates highly anisotropic thermal, electrical, and optical behaviors. The incorporation of SWCNTs into solid-state devices and optoelectronics to take advantage of these anisotropic behaviors, however, requires researchers to macroscopically align SWCNT ensembles from solution.  Recently, the goal of producing wafer-scale aligned nanotube films was demonstrated using a human-controlled, vacuum filtration process.  Unfortunately, this has proven difficult to replicate and augment.  Here, we incorporate machine vision, a pressure feedback loop, and parallelized filtration units with SWCNTs of high quality to scale-up and optimize aligned film throughput.  Using this platform, we produce sets of aligned SWCNT films with differing parameters to explore the alignment mechanism. We use a host of optical techniques to determine the nematic order parameter, S, a representation of alignment. Specifically, we show that disrupting the electrostatic environment around the SWCNT via the addition of NaCl suppresses nematic ordering.  This novel, automated SWCNT alignment capability provides a route for researchers to scale-up aligned nanotube film production.