Freeform Three-Dimensional Microstructures Using Single-Walled Carbon Nanotubes

Project Overview

Single-walled carbon nanotubes (SWCNTs) are hollow, tubular carbon molecules with exceptional mechanical, thermal, electrical, optical, and chemical properties. Current state-of-the-art production methods yield either loose powders or straight bundles. We sought to produce SWCNT microstructures that are curved and/or have otherwise complex trajectories. SWCNT microstructures with complex trajectories are expected to add an orthogonal dimension to conventional SWCNT material engineering, enabling development of material systems with unprecedented properties.

We focused on chemical vapor deposition synthesis of SWCNTs utilizing substrate bound catalysts that typically produce uniform vertically aligned SWCNTs. As the individual SWCNTs in the microstructure grow collectively, their growth rates are all the same, which results in straight microstructures. We sought to induce local growth rate variations, which would then lead to the microstructures curling over/deforming during growth. We adjusted the local SWCNT growth rate by varying the catalyst stack spatially, and successfully demonstrated that SWCNT microstructures with non-straight trajectories can be produced. This is the first demonstration of SWCNT microstructures with complex trajectories, which opens opportunities for applications requiring specific geometries.

Mission Impact

Lawrence Livermore National Laboratory (LLNL) has multiple SWCNT technologies in its arsenal for deployment in its critical missions. As an example, SWCNT yarns have been utilized to suspend fuel capsules in nuclear fusion experiments. The developed freeform SWCNT microstructures in this project will add another tool to LLNL's toolbelt regarding what geometry is possible to achieve with SWCNT materials. Multiple programs (Global Security, National Ignition Facility, Engineering, Physical and Life Sciences) are expected to benefit from the results of this project and follow on research, by harnessing the improved properties of material systems deployed to meet their goals. Further funding and personnel can be attracted to LLNL as the technology finds uses in LLNL's mission critical development projects. Moreover, other DOE/NNSA organizations and even the broad scientific community will be able to apply this technology to meet their goals, provided that the technical details are made available to them.