Macroscopic 1D vdW heterostructures and their potential applications. (A) Various types of starting SWCNTs that may serve as the skeleton for the fabrication of macroscopic 1D vdW heterostructures; (B) schematic showing the expected geometry of macrostructures; (C) optical images of a macroscopic SWCNT-BNNT film self-suspending on a silicon frame and a SWCNT-BNNT-MoS₂ heterostructure film on a ceramic washer (scale bar 5 mm); (D) possible band alignments of a hetero-nanotube-based photovoltaic device.