Wet-Spun Graphene Sheets as Flexible Heat Spreaders for Efficient Thermal Management

With the shrinkage of chip size and the increase of integration density, chip heat flux increases dramatically. Efficient heat dissipation becomes critical for the performance, reliability and service life of electronics. Therefore, advanced lateral heat spreader materials such as carbon allotropes and their derivatives are highly desirable in modern electronics. Graphene attracts great attention as a lateral heat spreader material due to its unique thermal transfer property (theoretical thermal conductivity ca. 5300 W m(-1) K-1 ) and its natural two-dimensional (2D) structure. However, an efficient method to accomplish large scale production and ordered assembly structures of graphene sheets is critical for real application in heat dissipation in electronics. Conventional production methods to produce graphene sheets such as filtration method, solvent evaporation method, chemical vapor deposition, electrostatic spray deposition etc. have some limitations-long production time, high energy consumption and great difficulties in controlling the sheet geometry, for instance. In this contribution, graphene sheets were fabricated by a wet-spinning method of graphene oxide (GO) solution followed by chemical reduction of GO to reduced graphene oxide (rGO). The wet-spinning method was able to produce graphene sheets in a high rate (similar to 1.2 m/min) and in different dimensions. Here sheets with different thickness (8 mu m and 16 mu m) are demonstrated. A series of characterizations are performed for the produced GO and rGO sheets including their Raman and infrared spectra, X-ray diffraction pattern, scanning microscopic pictures and atomic force microscopic pictures. These data show that the reduction is sufficient and the GO sheets are piled up parallel during the wet-spinning process, which is beneficial for the lateral heat transport. The rGO has an in-plane electrical conductivity ca. 6848.41 S/m and thermal conductivity ca. 1024.86 W m(-1)K(-1) . In addition, the film displayed excellent heat dissipation performance when attached on top of a light emitting diode (LED) light strip. The research results indicate our approach is facile and capable of fabricating scalable and controllable heat spreader materials with high performance.