Failure mechanism of Ag nanowire-coated conductive transparent electrode for wearable devices under folding and torsional fatigue condition

Foldable electrodes with a low electrical resistance and high mechanical fatigue resistance are expected for next generation electronic devices. The failure mechanism of fatigued Ag nanowire (AgNW) electrode and its effect on the electrical degradation was investigated. Instead of bending fatigue of previous research, electrical resistance was measured in-situ during folding and torsion fatigue tests up to 100,000 cycles in this study. The damage mechanism of the AgNW including welding of network junction, nanocracking, and fragmentation were revealed by microscopic observation of the fatigued or interrupted specimens. Under the high strain folding fatigue condition, electrical resistance was observed to decrease initially and then subsequently to keep increasing. This initial decrease is attributed to the junction welding phenomenon and the continuous increase is due to nanocracking or fragmentation. For torsion fatigued electrodes, electrical resistance increased with increasing torsional degree. The increase in resistance with torsional degree was correlated with number of fragments of AgNW. Under the functional failure criterion of 10% change in electrical resistance, feasibility for foldable and wearable applications of the AgNW electrode was considered.