Printable elastic conductors by in situ formation of silver nanoparticles from silver flakes

Printable elastic conductors promise large-area stretchable sensor/actuator networks for healthcare, wearables and robotics. Elastomers with metal nanoparticles are one of the best approaches to achieve high performance, but large-area utilization is limited by difficulties in their processability. Here we report a printable elastic conductor containing Ag nanoparticles that are formed in situ , solely by mixing micrometre-sized Ag flakes, fluorine rubbers, and surfactant. Our printable elastic composites exhibit conductivity higher than 4,000 S cm −1 (highest value: 6,168 S cm −1 ) at 0% strain, and 935 S cm −1 when stretched up to 400%. Ag nanoparticle formation is influenced by the surfactant, heating processes, and elastomer molecular weight, resulting in a drastic improvement of conductivity. Fully printed sensor networks for stretchable robots are demonstrated, sensing pressure and temperature accurately, even when stretched over 250%. Printing and heating of a fluorinated elastomer mixed with silver flakes, a fluorine surfactant and methylisobutylketone leads to the formation of in situ silver nanoparticles, which boost the conductivity of this highly stretchable composite material.