Controlled growth of crossed ultralong carbon nanotubes by gas flow

Carbon nanotubes (CNTs) work as the promising components of miniature electromechanical systems due to their excellent performances from individual to bundle scales. But it’s challenging to achieve precise patterning at nanoscale resolution with controlled position and orientation. Here, we demonstrate a fluidic strategy to interlace one-dimensional (1D) ultralong CNTs into the crossed pattern in a one-step in-situ process. Semi-circular substrates of different diameters were placed in front of the growth substrate to change the path and momentum of gas flow. Such flow perturbation caused by substrates could be markedly reflected within a micro-channel reactor, which led to formation of crossed ultralong CNTs at definite positions. Furthermore, precise control over the crossing angle as well as the diameter distribution of CNTs was achieved by varying the CNT length and diameter of semi-circular substrates. Our strategy has offered a feasible route for production of crossed ultralong CNTs and will contribute to multidimensional fluidic assembly of flexible nanomaterials.