Silver flake/polyaniline composite ink for electrohydrodynamic printing of flexible heaters

Printed flexible electrical heaters with excellent heating performance and mechanical durability are highly desirable for deicing and wearable thermotherapy devices. However, the performance of the conventional heaters is stilled limited by low-resolution fabrication methods when applied in high-precision heating in desirable regions. Moreover, the poor conductivity and mechanical stability of the ink also increase the power consumption. Herein, a high-resolution (45 μm) heater with low power consumption was fabricated by a facile electrohydrodynamic (EHD) printing method. A highly printable and stable hybrid conductive ink was obtained by doping PANI nanoparticles into silver flake/thermoplastic polyurethane (TPU) composite. After adding 0.5 wt% PANI nanoparticles into 40 wt% silver flake/TPU composite and low temperature sintering (80 °C), the bulk resistivity decreased from 96.03 × 10 Ω·m to 1.26 × 10 Ω·m. Thanks to the ultrahigh conductivity of the ink, the EHD printed flexible heater shows high saturation temperature (127.0 °C) under low applied voltage (2 V), wide heating range (33.9 °C~127.0 °C) under a small range of driving voltages (0.5 V ~ 2.0 V), the rapid response time (20 s) and excellent repeatability during 10-time cyclic heating-cooling possess. Furthermore, the printed flexible heaters exhibit great flexibility and durability. The resistance of the heater remains stable after 3000 outer bending cycles with a radius of 0.5 mm, indicating outstanding mechanical stability. Moreover, the heater can be attached to the human body, showing the potential for emerging wearable electronic applications.