Highly stretchable and conductive conductors based on Ag flakes and polyester composites

In stretchable electronics, the development of conductors that have high stretchability and low electrical resistance is a crucial technical issue. In this study, we developed a highly stretchable Ag conductor composed of Ag flakes and a polyester binder. We focused on the IR-curing technique to develop the stretchable Ag conductor, which was printed on the polyurethane elastomer substrate. The effects of the temperature and duration of curing on the electrical resistance and electromechanical properties of the Ag conductor were investigated. The electromechanical properties of the stretchable Ag conductor were evaluated in stretching, bending, and cyclic endurance tests. We achieved stretchable conductors with a low sheet resistance of 46 mΩ/sq., a superior stretchability of 150%, and a bending radius of 1 mm. The Ag conductor also exhibited outstanding mechanical durability in the cyclic stretching and bending endurance tests. In this study, the optimized IR-curing duration and temperature were 5 min and 130 °C, respectively. However, in future research, the curing duration could be further reduced by the optimization of the IR parameters. The results of the pencil hardness test and the peel-off adhesion test (i.e., the cross-cut test) indicated that the stretchable Ag conductor had excellent hardness and strength of adhesion between the conductor and the substrate.