Hybrid Metal–Carbon Ink for Printed Stretchable Temperature Sensors

Conductive polymer composites for printed stretchable temperature sensors must remain functional during many strain cycles despite unavoidable changes in their microstructure and thus the electrically conductive network. In this study, we introduce screen‐printable inks with electrical conductivities and temperature coefficients of resistance (TCR, α ) that are suitable for application in temperature sensors while retaining thermal and mechanical stability upon stretching the printed sensors. Silver flakes (AgF) and carbon black (CB) or graphite flakes (GR) at different ratios were combined as conductive fillers in dragon skin (DS) elastomer and screen printed. Their electrothermal properties were characterized within the temperature range of 20°C–120°C. Samples with constant α in suitable ranges were selected and characterized electrically for stability during thermal cycling and mechanically during 30 000 strain cycling. The DS‐AgF‐CB12‐180°C and DS‐AgF‐GR10‐180°C composites exhibited linear resistance changes with α = 2.29 × 10 −3 /°C and 1.75 × 10 −3 /°C, respectively. The resistance of DS‐AgF‐GR drifted below 2% over 10 thermal cycling and relative resistance changes ( R/R 0 ) increased up to 8 after 30 000 strain cycling at 0%–10%. We show that the carbon particles modify the metal–matrix interactions in the hybrid composites, thus increasing stability and reliability of temperature sensing.