# A Review on the Deformation Behavior of Silver Nanowire Networks under Many Bending Cycles
## 6 Conclusions  
In summary, silver nanowire electrodes showed considerably better reliability, compared to the competitors, such as ITO or Ag thin films, under a high number of bending cycles. Such excellent mechanical reliability was secured even after applying protective layers, such as RGO or metal oxides, on the silver nanowires. Thus, the resistance increase in silver nanowire-based electrodes under a high number of bending cycles was much lower than that of ITO or silver thin films, as summarized in Table 1. The enhanced mechanical reliability was due to the different deformation behavior of silver nanowire  
Figure 19: Resistance change of silver nanowire networks with and without Al\({}_{2}\)O\({}_{3}\) as a function of (**a**) different exposure time at 85 \({}^{\circ}\)C and (**b**) different annealing temperature. Change in (**c**) transmittance and haze and (**d**) sheet resistance of silver nanowire networks with different Al\({}_{2}\)O\({}_{3}\) coating thickness. Reproduced with permission from ref. [52]. Copyright 2019, Elsevier. Figure 18: Resistance change of the silver nanowire network with Al\({}_{2}\)O\({}_{3}\), TiO\({}_{2}\), and HfO\({}_{2}\) overcoating with different thicknesses. Reproduced with permission from ref. [52]. Copyright 2019, Elsevier. electrodes from that of the thin film-type materials, where dislocation accumulation at the substrate-nanowire interface is difficult to form, which suppresses the crack initiation/propagation. In addition, the silver nanowire network has the geometrical advantage in that it can accommodate the imposed strain by stretching its structure. In addition, to provide in-depth insight of the deformation behavior of silver nanowire electrodes under high-cycle bending, the following critical points were discussed through this review as described in Figure 20: (1) the failure mode of silver nanowires under high-cycle bending, (2) enhanced reliability by the mechanical welding of silver nanowires, (3) the deformation mode change under different strains of tension and compression, and (4) the effect of protective coating on the mechanical reliability of silver nanowire electrodes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Materials** & **\# of Bending Cycles** & **Strain** & **R\(-\)R\({}_{0}\)/R\({}_{0}\) (\%)** & **Ref.** \\ \hline \multirow{8}{*}{Silver nanowire} & 200,000 & 2\% & \(-\)2\% & [42] \\ \cline{2-5}  & & 1\% & \(\sim\)1.5\% & \\ \cline{2-5}  & & 2\% & \(-\)3\% & [28] \\ \cline{2-5}  & & 3\% & \(-\)10\% & \\ \cline{2-5}  & & 4\% & \(\sim\)18.8\% & \\ \cline{2-5}  & 800,000 & 1.5\% & \(\sim\)2\% & [49] \\ \hline Silver nanowire/rGO & 800,000 & 1.5\% & \(\sim\)3\% & [49] \\ \hline Silver nanowire/Al\({}_{2}\)O\({}_{3}\) (5 nm) & 300,000 & 2.5\% & \(\sim\)25\% & \\ \hline Silver nanowire/TiO\({}_{2}\) (5 nm) & 300,000 & 2.5\% & \(\sim\)25\% & \\ \hline Silver nanowire/HfO\({}_{2}\) (5 nm) & 300,000 & 2.5\% & \(\sim\)25\% & \\ \hline Silver thin film (100 nm) & 500,000 & 1\% & \(\sim\)78\% & [28] \\ \hline ITO (100 nm) & 500 & 2.5\% & \(\sim\)6000\% & [24] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the change in resistance of different materials after high-cyclic bending. Figure 20: Graphical summary of the review paper. Some of the graphs are reproduced with permission from ref. [28]. Copyright 2014, Wiley. Reproduced with permission from ref. [43]. Copyright 2016, Elsevier. As discussed above, silver nanowires have attracted significant attention for application as transparent electrodes of flexible electronic devices. The different deformation mechanisms in nanosized wires require an in-depth study of the deformation behavior of silver nanowire electrodes. In particular, understanding the deformation mechanism of materials in repetitive and various types of deformation should precede their application in real-life electronics, which must be resilient against various types of deformation and millions of repetitions of deformation.