. Formation of Cu nanowires directed by liquid-crystalline structure of the medium^[14]

. SEM images and diameter distribution of Cu nanowires synthesized by using different halide ions^[16] (a, e) 2.6 mmol Cl^-; (b,f) 2.0 mmol Cl^-; (c,g) 1.6 mmol Cl^-; (d,h) 1.6 mmol Br^-

. (A) SEM image of Cu-Ni NWs with inset showing high resolution SEM image of Cu-Ni NWs; (B) Dark field optical microscopy images of Cu-Ni NWs; (C-H) The distribution of Cu and Ni elements of Cu-Ni NWs with different contents of nickel^[23]

. Schematic diagram of the vaccum transfer method (a)^[35], the spray-coating method (b)^[36], the meyer rod coating method (c)^[37], and the roll-to-roll coating method (d)^[37]

. (a-c) Schematic diagram of the experimental setup of a typical plasma treatment process; (d) SEM image of the nanowire junction after plasma treatment; (e) Current-voltage measurement of LED lamps connected by stretchable Cu NW conductors at various strains. Insets are digital photos of the whole setup at 0 and 250% strain^[48]

. Schematic diagram (a) of the preparation procedure of Cu NWs/PA electrode. SEM (b), TEM (c), HRTEM (d) and EELS spetra (e) of the Cu NWs film after TiO₂ nanopartical sol treatment. Raman spectra (f) of Cu NWs before post-treating, after H₂ plasma treatment and TiO₂ nanopartical sol treatment. Plot of the transmittance (at a wavelength of 550 nm) with respect to the sheet resistance (g) for films of Cu NWs with H₂ annealing, H₂ plasma treatment and TiO₂ nanopartical sol treatment. Sheet resistance variation (h) of the commercial ITO/PET and Cu NWs/PA electrodes during the bending test of 10⁴ cycles^[53]

. (a) Time-dependent temperature curves of Cu NW-1000 on PET films at input voltages of 1.5-5 V under ambient conditions; (b) PET/ITO transparent heaters during 10⁴ cycles of bending tests; (c) Infrared photograph and (d) application examples of Cu NW-based stretchable heater^[61]

Table 1. Summary of representitive synthetic methods of Cu nanowires