# Stability of Silver-Nanowire-Based Flexible Transparent Electrodes under Mechanical Stress
## 3 Results and Discussion
The AgNW-exposed electrode also showed a much smaller increase in the RMS roughness than that of the ITO/PET electrode in the AFM image. The RMS roughness values before and after applying the compressive stress were 9.8 and 12.9 nm, respectively. The SEM and AFM images indicate that although some of the AgNW s can be bent or broken owing to compressive stress, this is rare. Therefore, the surface morphology can generally be maintained, resulting in a minor increase in the sheet resistance. The AgNW-embedded electrode showed a more stable surface morphology under compressive stress than the ITO/PET and AgNW-exposed electrodes, regardless of the type of polymer used for the embedding process. Figure 4 shows SEM and AFM images of the AgNW-embedded electrodes prepared with NOA  
RMS roughness of 1.6 and 2.7 nm, respectively, before and after compressive stress was applied, thereby maintaining a low level. In conclusion, the AgNW-embedded electrode exhibited low resistance even after applying compressive stress 1000 times because the effect of compressive stress on the surface morphology is too small to generate cracks. This is attributed to the ability of the polymer to release the applied compressive stress and maintain the AgNW network. Next, the sheet resistance was measured as a function of the number of tensile stresses to examine the effect of tensile stress on the sheet resistance of the flexible electrodes. Figure 5 shows the change in sheet resistance due to the application of tensile stress to the ITO electrode on the PET film, the AgNW-exposed electrode, and the AgNW-embedded  
Figure 4: (**a**–**d**) SEM and (**e**,**h**) AFM images of AgNW-embedded electrode in (**a**,**b**,**e**,**f**) NOA63 and (**c**,**d**,**g**,**h**) NOA71 (**a**,**c**,**e**,**g**) before and (**b**,**d**,**f**,**h**) after applying compressive stress. The RMS roughness values of the AgNW-embedded electrode in NOA63 were 3.7 nm and 3.4 nm before and after applying compressive stress, respectively. The RMS roughness values of the AgNW-embedded electrode in NOA71 were 1.6 nm and 2.7 nm before and after applying compressive stress, respectively. Figure 3: (**a**,**b**) SEM and (**c**,**d**) AFM images of AgNW-exposed electrode on a PET film (**a**,**c**) before and (**b**,**d**) after applying compressive stress. The RMS roughness values before and after applying compressive stress were 9.8 nm and 12.9 nm, respectively. electrode, which were prepared using NOA63 and NOA71. As shown in Figure 5a, the sheet resistance of the ITO electrode rapidly exceeded 10,000 \(\Omega\)/sq even when the tensile stress was applied just 100 times. When the tensile stress was applied 1000 times, the sheet resistance was 87,833 \(\Omega\)/sq, indicating insulating characteristics. Considering that the sheet resistance was approximately 3173 \(\Omega\)/sq when compressive stress was applied 1000 times, the increase in sheet resistance by the application of tensile stress is very large. The AgNW-exposed electrode also showed an increase in sheet resistance when tensile stress was applied. Similar to the ITO electrode, the sheet resistance increased at a higher rate when tensile stress was applied than when compressive stress was applied. As shown in Figure 5b, the sheet resistance was 573 \(\Omega\)/sq after applying tensile stress 500 times and 1856 \(\Omega\)/sq after applying tensile stress 100 times. Similar to the application of compressive stress, the AgNW-embedded electrode exhibited the smallest increase in sheet resistance when tensile stress was applied. When NOA63 was used as the polymer in the embedding process, the initial sheet resistance was 106 \(\Omega\)/sq. The sheet resistance increased to 281 \(\Omega\)/sq when tensile stress was applied 500 times and to 296 \(\Omega\)/sq when tensile stress was applied 1000 times. When adopting NOA71 as an embedding polymer, the sheet resistance was 93 \(\Omega\)/sq. When tensile stress was applied 500 times and 1000 times, the sheet resistance changed to 156 \(\Omega\)/sq and 159 \(\Omega\)/sq, respectively.