On the basis of the rational analysis about the fluidic property of the system, an ultralow gas flow chemical vapor deposition (CVD) strategy was designed to prepare large-scale horizontally aligned ultralong single-walled carbon nanotube (SWNT) arrays. SWNT arrays could be well obtained under extremely low feeding flow of 1.5 sccm in a 1 in. quartz tube reactor. It was confirmed that the tubes grew floatingly and could cross microtrenches or climb over micro-obstacles in ultraslow gas flow. SWNTs arrays also could be formed no matter the substrate was placed vertically or upside down. The growth mechanism was discussed. Both the buoyancy effect induced by gas temperature/density difference and gas flow stability played dominant roles. More attractively, simultaneous batch-scale preparation of SWNT arrays was realized by the ultralow gas flow strategy. This new strategy turns to be more abstemious, efficient, promising, and flexible compared with the high gas flow rate fast-heating CVD processes.

Gas flow is used to guide the growth of ultralong single-walled carbon nanotubes (SWCNTs) with complex shapes. Large-area cross-shaped networks of ultralong SWCNTs are obtained by a two-step chemical vapor deposition process. Also non-straight SWCNTs of different shapes are prepared by modifying the gas flow with tiny barriers. The shapes of the SWCNTs replicate the streamline patterns accordingly. The SWCNTs with designed patterns and shapes may be used in high performance nanoelectronics.

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