Molecular-Level Contact of Graphene/Silver Nanowires through Simultaneous Dispersion for a Highly Stable Wearable Electrothermal Heater

Abstract

Silver nanowires (AgNWs) with low sheet resistances are excellent potential candidates for high-performance wearable electrothermal heaters operated through Joule heating. However, the thermal oxidation and electrical instability of AgNWs caused by high contact resistance and poor adhesion to different substrates considerably limit their use in devices. Graphene is used in a AgNW/graphene hybrid owing to its low oxygen permeability, lower contact resistance with AgNWs, and good van der Waals interactions. Molecular-level contacts between AgNWs and graphene must be achieved to maximize the synergy of these properties. In this study, a multifunctional polymer possessing styrene sulfonate-based copolymer and disulfide groups is designed; these groups allow the simultaneous dispersion of AgNWs and graphene in an aqueous solution through self-assembly. Since this polymer promotes molecular-level contact between AgNWs and graphene, the oxidation and Joule-heating stabilities of the hybrid dramatically increase. In addition, a freestanding AgNW/graphene film is readily prepared, exhibiting good attachable properties on various substrates and superior stability under harsh conditions (85 degrees C and 85% relative humidity for 7 days). The AgNW/graphene hybrid film displays a low sheet resistance (0.36 +/- 0.02 omega sq(-1)) with good performance as a high-performance electrothermal heater (200 degrees C at 1.5 V).