PVA-Concentration-Regulated Conductive Inks for Low-Voltage-Driven Flexible Joule Heating Devices with Tunable Performance and Mechanical Robustness

Polyvinyl alcohol (PVA) concentration plays a key role in the printability, electrical conductivity, and electrothermal performance of conductive inks for flexible Joule heating devices. In this work, PEDOT:PSS/Cu@Ag composite inks with 5 wt%, 10 wt%, and 15 wt% PVA were prepared and systematically investigated. The viscosities of the three solutions were 454.09, 884.14, and 2917.01 mPa·s, respectively. Flexible devices were fabricated on polyimide substrates via doctor-blade printing and thermal curing. The 10 wt% PVA-based device exhibited the optimal performance, reaching 100°C at approximately 3 V. By designing single-line, series, and shunt electrode configurations, the shunt-connected device achieved the highest heating temperature of 110.7°C at 3 V. Bending tests demonstrated that the device maintained stable circuit continuity under a bending radius down to 2 mm at 3 V driving. This study provides an effective strategy for designing low-voltage-driven, mechanically robust flexible heating devices for wearable electronic applications.