Patterns of Carbon Nanotubes by Flow-Directed Deposition on Substrates with Architectured Topographies

We
develop and perform continuum mechanics simulations of carbon
nanotube (CNT) deployment directed by a combination of surface topography
and rarefied gas flow. We employ the discrete elastic rods method
to model the deposition of CNT as a slender elastic rod that evolves
in time under two external forces, namely, van der Waals (vdW) and
aerodynamic drag. Our results confirm that this self-assembly process
is analogous to a previously studied macroscopic system, the “elastic
sewing machine”, where an elastic rod deployed onto a moving
substrate forms nonlinear patterns. In the case of CNTs, the complex
patterns observed on the substrate, such as coils and serpentines,
result from an intricate interplay between van der Waals attraction,
rarefied aerodynamics, and elastic bending. We systematically sweep
through the multidimensional parameter space to quantify the pattern
morphology as a function of the relevant material, flow, and geometric
parameters. Our findings are in good agreement with available experimental
data. Scaling analysis involving the relevant forces helps rationalize
our observations.