Fabrication of silver plated copper powders to apply in flexible conductive films for strain sensor

Copper powders have high electrical conductivity; however, ultrafine copper powders have a large specific surface area and are easy to oxidize, which greatly reduce the conductivity of copper. In this paper, silver plated copper (Ag@Cu) powders were prepared to avoid the oxidation of copper powders and the average particle size of Ag@Cu powders is about 1.19 μm. The Ag@Cu powders are blended with polydimethylsiloxane (PDMS) to form a paste, which is printed and cured to form Ag@Cu/PDMS conductive films. When the content of Ag@Cu conductive filler is 60wt%, the resistivity of conductive film is 1.6 × 10 –2 Ω·cm. The Ag@Cu/PDMS films possess super stretchability, excellent electrical conductivity and favorable long stability. The conductive films have excellent reversible tensile, torsional and bending abilities and can be used as flexible conductors. Then, using this Ag@Cu/PDMS conductive film as a conductive layer, a sandwich structured PDMS-Ag@Cu/PDMS-PDMS flexible strain sensor was fabricated. The relative resistance variation of the strain sensor under the cycles of stretching and releasing indicates that the strain sensor has excellent stability, sensitivity and repeatability (gauge factor of 2.83 and 2.43 in strain of 15% and 30%). The uniform sensor signals suggest a remarkable sensitive of the strain sensors and have potential applications in human motion monitoring systems and electronic skins.