We report a simple, versatile, and wafer-scale water-assisted transfer printing method (WTP) that enables the transfer of nanowire devices onto diverse nonconventional substrates that were not easily accessible before, such as paper, plastics, tapes, glass, polydimethylsiloxane (PDMS), aluminum foil, and ultrathin polymer substrates. The WTP method relies on the phenomenon of water penetrating into the interface between Ni and SiO<sub>2</sub>. The transfer yield is nearly 100%, and the transferred devices, including NW resistors, diodes, and field effect transistors, maintain their original geometries and electronic properties with high fidelity.
This paper describes a simple and yet rapid flame synthesis method to produce one dimensional metal oxide
nanostructures by directly oxidizing metals in the post-flame region of a flat flame. α-Fe<sub>2</sub>O<sub>3</sub> nanoneedles grow in the
post-flame region by a solid diffusion mechanism, are highly crystalline, and are aligned perpendicularly to the substrate,
with a large surface coverage density. The growth rate of the nanostructures is almost two orders of magnitude larger
than those demonstrated previously in furnaces or on hotplates. The rapid growth rate is attributed to the large initial
heating rate of the metal substrate in the flame, which generates thin and porous oxide layers that greatly enhance the
diffusion of the deficient species to the nanostructure growth site.