Supersonically sprayed carbon nanotubes and silver nanowires as efficient heat spreaders and cooling films

Abstract

With the ever-decreasing size of portable electronics to achieve greater versatility, the power density of electronic devices has increased substantially, to the point where efficient cooling has become a major concern for achieving stable device operation. Herein, we introduce a heat-dissipating film coated with carbon nanotubes (CNTs) entangled with silver nanowires (AgNWs), prepared by supersonic spraying. Low thermal resistance was obtained from the strong adhesion between the deposited nanomaterials and the substrate. The optimal hybrid film for achieving maximal cooling was identified by varying the number of spraying sweeps and the composition of the nanomaterials. The hybrid film, comprising both CNTs and AgNWs, afforded superior cooling owing to its improved thermal conductivity. Surface-texturing of the film also significantly impacted the convective-cooling performance. In addition, the superior heat-spreading capability of the hybrid film was demonstrated by comparing infrared images of the bare substrate, pure CNTs, and hybrid CNT/AgNW films. The wettability of these films was also studied to identify the wetting condition that would provide the maximum heat transfer. The hybrid CNT/AgNW film possessed the most hydrophilic surface, providing the most efficient spray-cooling scenario. The hydrophilic surface captured and held the sprayed droplets firmly throughout the process. Hence, these CNT/AgNW hybrid films represent a commercially viable solution for addressing hotspots in portable electronic devices.