Fig. 4.

Electrothermal properties of the flexible Cu mesh film (Coverage ratio = 15.3%, thickness = 2.5 μm). a Time-dependent surface temperatures of Cu mesh film under different supplied voltages. b Corresponding current values to different supplied voltages (Compliance currents = 1.05 A). c Infrared images of the Cu mesh film at different supplied voltages. d Time-varying surface temperature of the Cu mesh films with different coverage ratios at 0.50 V supplied voltage. e Temperature stability of the film during 5 h under continuous 0.50 V voltage supplied. Insets shows that a Cu mesh film is used as a heater. f Thermal response of the film under cycle-to-cycle voltage on–off at 0.50 V. g Infrared images of the Cu mesh film under different tensile strains (ε = 0%, 10%, 20% and 30%)