Highly flexible, transparent and conductive ultrathin silver film heaters for wearable electronics applications

We fabricate highly flexible and conducive (sheet resistance of 6.2 Ohm/sq.) ultrathin Ag film heaters sandwiched by ZnO layers to achieve high visible light transparency (average transmittance of 90.2%). The transparent resistive heaters exhibit high spatial thermal uniformity, fast thermal response time, outstanding heater durability, robustness under mechanical bending and low-voltage operation enabled by the high conductivity. The excellent heating capability was evident with various heating tests either in the bent or unbent form, which qualifies this heating element for various wearable electronics including biomedical devices. The electrical parameters required to reach various temperatures were evaluated based on the square-shaped heaters having areas in the range of 25-2,025 mm(2), which confirms the suitability of the heating element for large-scale (200 mm x 200 mm) applications via a direct connection with a portable rechargeable battery having the output dc 12 V.